Merging upstream version 1.71.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

28 files changed, 624 insertions, 534 deletions

diff --git a/compiler/rustc_mir_build/Cargo.toml b/compiler/rustc_mir_build/Cargo.toml
index f24b165d7..58449ee9e 100644
--- a/compiler/rustc_mir_build/Cargo.toml
+++ b/compiler/rustc_mir_build/Cargo.toml
@@ -14,6 +14,7 @@ rustc_apfloat = { path = "../rustc_apfloat" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_index = { path = "../rustc_index" }
 rustc_errors = { path = "../rustc_errors" }
+rustc_fluent_macro = { path = "../rustc_fluent_macro" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_infer = { path = "../rustc_infer" }
 rustc_macros = { path = "../rustc_macros" }
diff --git a/compiler/rustc_mir_build/messages.ftl b/compiler/rustc_mir_build/messages.ftl
index f346cd483..cb265cf2c 100644
--- a/compiler/rustc_mir_build/messages.ftl
+++ b/compiler/rustc_mir_build/messages.ftl
@@ -1,62 +1,40 @@
-mir_build_unconditional_recursion = function cannot return without recursing
-    .label = cannot return without recursing
-    .help = a `loop` may express intention better if this is on purpose
-
-mir_build_unconditional_recursion_call_site_label = recursive call site
-
-mir_build_unsafe_op_in_unsafe_fn_call_to_unsafe_fn_requires_unsafe =
-    call to unsafe function `{$function}` is unsafe and requires unsafe block (error E0133)
-    .note = consult the function's documentation for information on how to avoid undefined behavior
-    .label = call to unsafe function
-
-mir_build_unsafe_op_in_unsafe_fn_call_to_unsafe_fn_requires_unsafe_nameless =
-    call to unsafe function is unsafe and requires unsafe block (error E0133)
-    .note = consult the function's documentation for information on how to avoid undefined behavior
-    .label = call to unsafe function
-
-mir_build_unsafe_op_in_unsafe_fn_inline_assembly_requires_unsafe =
-    use of inline assembly is unsafe and requires unsafe block (error E0133)
-    .note = inline assembly is entirely unchecked and can cause undefined behavior
-    .label = use of inline assembly
+mir_build_adt_defined_here = `{$ty}` defined here
 
-mir_build_unsafe_op_in_unsafe_fn_initializing_type_with_requires_unsafe =
-    initializing type with `rustc_layout_scalar_valid_range` attr is unsafe and requires unsafe
-    block (error E0133)
-    .note = initializing a layout restricted type's field with a value outside the valid range is undefined behavior
-    .label = initializing type with `rustc_layout_scalar_valid_range` attr
+mir_build_already_borrowed = cannot borrow value as mutable because it is also borrowed as immutable
 
-mir_build_unsafe_op_in_unsafe_fn_mutable_static_requires_unsafe =
-    use of mutable static is unsafe and requires unsafe block (error E0133)
-    .note = mutable statics can be mutated by multiple threads: aliasing violations or data races will cause undefined behavior
-    .label = use of mutable static
+mir_build_already_mut_borrowed = cannot borrow value as immutable because it is also borrowed as mutable
 
-mir_build_unsafe_op_in_unsafe_fn_extern_static_requires_unsafe =
-    use of extern static is unsafe and requires unsafe block (error E0133)
-    .note = extern statics are not controlled by the Rust type system: invalid data, aliasing violations or data races will cause undefined behavior
-    .label = use of extern static
+mir_build_assoc_const_in_pattern = associated consts cannot be referenced in patterns
 
-mir_build_unsafe_op_in_unsafe_fn_deref_raw_pointer_requires_unsafe =
-    dereference of raw pointer is unsafe and requires unsafe block (error E0133)
-    .note = raw pointers may be null, dangling or unaligned; they can violate aliasing rules and cause data races: all of these are undefined behavior
-    .label = dereference of raw pointer
+mir_build_bindings_with_variant_name =
+    pattern binding `{$name}` is named the same as one of the variants of the type `{$ty_path}`
+    .suggestion = to match on the variant, qualify the path
 
-mir_build_unsafe_op_in_unsafe_fn_union_field_requires_unsafe =
-    access to union field is unsafe and requires unsafe block (error E0133)
-    .note = the field may not be properly initialized: using uninitialized data will cause undefined behavior
-    .label = access to union field
+mir_build_borrow = value is borrowed by `{$name}` here
 
-mir_build_unsafe_op_in_unsafe_fn_mutation_of_layout_constrained_field_requires_unsafe =
-    mutation of layout constrained field is unsafe and requires unsafe block (error E0133)
-    .note = mutating layout constrained fields cannot statically be checked for valid values
-    .label = mutation of layout constrained field
+mir_build_borrow_of_layout_constrained_field_requires_unsafe =
+    borrow of layout constrained field with interior mutability is unsafe and requires unsafe block
+    .note = references to fields of layout constrained fields lose the constraints. Coupled with interior mutability, the field can be changed to invalid values
+    .label = borrow of layout constrained field with interior mutability
 
-mir_build_unsafe_op_in_unsafe_fn_borrow_of_layout_constrained_field_requires_unsafe =
-    borrow of layout constrained field with interior mutability is unsafe and requires unsafe block (error E0133)
+mir_build_borrow_of_layout_constrained_field_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
+    borrow of layout constrained field with interior mutability is unsafe and requires unsafe function or block
     .note = references to fields of layout constrained fields lose the constraints. Coupled with interior mutability, the field can be changed to invalid values
     .label = borrow of layout constrained field with interior mutability
 
-mir_build_unsafe_op_in_unsafe_fn_call_to_fn_with_requires_unsafe =
-    call to function `{$function}` with `#[target_feature]` is unsafe and requires unsafe block (error E0133)
+mir_build_borrow_of_moved_value = borrow of moved value
+    .label = value moved into `{$name}` here
+    .occurs_because_label = move occurs because `{$name}` has type `{$ty}` which does not implement the `Copy` trait
+    .value_borrowed_label = value borrowed here after move
+    .suggestion = borrow this binding in the pattern to avoid moving the value
+
+mir_build_call_to_fn_with_requires_unsafe =
+    call to function `{$function}` with `#[target_feature]` is unsafe and requires unsafe block
+    .note = can only be called if the required target features are available
+    .label = call to function with `#[target_feature]`
+
+mir_build_call_to_fn_with_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
+    call to function `{$function}` with `#[target_feature]` is unsafe and requires unsafe function or block
     .note = can only be called if the required target features are available
     .label = call to function with `#[target_feature]`
 
@@ -70,55 +48,24 @@ mir_build_call_to_unsafe_fn_requires_unsafe_nameless =
     .note = consult the function's documentation for information on how to avoid undefined behavior
     .label = call to unsafe function
 
-mir_build_call_to_unsafe_fn_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
-    call to unsafe function `{$function}` is unsafe and requires unsafe function or block
-    .note = consult the function's documentation for information on how to avoid undefined behavior
-    .label = call to unsafe function
-
 mir_build_call_to_unsafe_fn_requires_unsafe_nameless_unsafe_op_in_unsafe_fn_allowed =
     call to unsafe function is unsafe and requires unsafe function or block
     .note = consult the function's documentation for information on how to avoid undefined behavior
     .label = call to unsafe function
 
-mir_build_inline_assembly_requires_unsafe =
-    use of inline assembly is unsafe and requires unsafe block
-    .note = inline assembly is entirely unchecked and can cause undefined behavior
-    .label = use of inline assembly
-
-mir_build_inline_assembly_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
-    use of inline assembly is unsafe and requires unsafe function or block
-    .note = inline assembly is entirely unchecked and can cause undefined behavior
-    .label = use of inline assembly
-
-mir_build_initializing_type_with_requires_unsafe =
-    initializing type with `rustc_layout_scalar_valid_range` attr is unsafe and requires unsafe block
-    .note = initializing a layout restricted type's field with a value outside the valid range is undefined behavior
-    .label = initializing type with `rustc_layout_scalar_valid_range` attr
-
-mir_build_initializing_type_with_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
-    initializing type with `rustc_layout_scalar_valid_range` attr is unsafe and requires unsafe function or block
-    .note = initializing a layout restricted type's field with a value outside the valid range is undefined behavior
-    .label = initializing type with `rustc_layout_scalar_valid_range` attr
+mir_build_call_to_unsafe_fn_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
+    call to unsafe function `{$function}` is unsafe and requires unsafe function or block
+    .note = consult the function's documentation for information on how to avoid undefined behavior
+    .label = call to unsafe function
 
-mir_build_mutable_static_requires_unsafe =
-    use of mutable static is unsafe and requires unsafe block
-    .note = mutable statics can be mutated by multiple threads: aliasing violations or data races will cause undefined behavior
-    .label = use of mutable static
+mir_build_confused = missing patterns are not covered because `{$variable}` is interpreted as a constant pattern, not a new variable
 
-mir_build_mutable_static_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
-    use of mutable static is unsafe and requires unsafe function or block
-    .note = mutable statics can be mutated by multiple threads: aliasing violations or data races will cause undefined behavior
-    .label = use of mutable static
+mir_build_const_param_in_pattern = const parameters cannot be referenced in patterns
 
-mir_build_extern_static_requires_unsafe =
-    use of extern static is unsafe and requires unsafe block
-    .note = extern statics are not controlled by the Rust type system: invalid data, aliasing violations or data races will cause undefined behavior
-    .label = use of extern static
+mir_build_const_pattern_depends_on_generic_parameter =
+    constant pattern depends on a generic parameter
 
-mir_build_extern_static_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
-    use of extern static is unsafe and requires unsafe function or block
-    .note = extern statics are not controlled by the Rust type system: invalid data, aliasing violations or data races will cause undefined behavior
-    .label = use of extern static
+mir_build_could_not_eval_const_pattern = could not evaluate constant pattern
 
 mir_build_deref_raw_pointer_requires_unsafe =
     dereference of raw pointer is unsafe and requires unsafe block
@@ -130,117 +77,46 @@ mir_build_deref_raw_pointer_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
     .note = raw pointers may be null, dangling or unaligned; they can violate aliasing rules and cause data races: all of these are undefined behavior
     .label = dereference of raw pointer
 
-mir_build_union_field_requires_unsafe =
-    access to union field is unsafe and requires unsafe block
-    .note = the field may not be properly initialized: using uninitialized data will cause undefined behavior
-    .label = access to union field
-
-mir_build_union_field_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
-    access to union field is unsafe and requires unsafe function or block
-    .note = the field may not be properly initialized: using uninitialized data will cause undefined behavior
-    .label = access to union field
-
-mir_build_mutation_of_layout_constrained_field_requires_unsafe =
-    mutation of layout constrained field is unsafe and requires unsafe block
-    .note = mutating layout constrained fields cannot statically be checked for valid values
-    .label = mutation of layout constrained field
-
-mir_build_mutation_of_layout_constrained_field_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
-    mutation of layout constrained field is unsafe and requires unsafe function or block
-    .note = mutating layout constrained fields cannot statically be checked for valid values
-    .label = mutation of layout constrained field
-
-mir_build_borrow_of_layout_constrained_field_requires_unsafe =
-    borrow of layout constrained field with interior mutability is unsafe and requires unsafe block
-    .note = references to fields of layout constrained fields lose the constraints. Coupled with interior mutability, the field can be changed to invalid values
-    .label = borrow of layout constrained field with interior mutability
-
-mir_build_borrow_of_layout_constrained_field_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
-    borrow of layout constrained field with interior mutability is unsafe and requires unsafe function or block
-    .note = references to fields of layout constrained fields lose the constraints. Coupled with interior mutability, the field can be changed to invalid values
-    .label = borrow of layout constrained field with interior mutability
-
-mir_build_call_to_fn_with_requires_unsafe =
-    call to function `{$function}` with `#[target_feature]` is unsafe and requires unsafe block
-    .note = can only be called if the required target features are available
-    .label = call to function with `#[target_feature]`
-
-mir_build_call_to_fn_with_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
-    call to function `{$function}` with `#[target_feature]` is unsafe and requires unsafe function or block
-    .note = can only be called if the required target features are available
-    .label = call to function with `#[target_feature]`
-
-mir_build_unused_unsafe = unnecessary `unsafe` block
-    .label = unnecessary `unsafe` block
-
-mir_build_unused_unsafe_enclosing_block_label = because it's nested under this `unsafe` block
-mir_build_unused_unsafe_enclosing_fn_label = because it's nested under this `unsafe` fn
-
-mir_build_non_exhaustive_patterns_type_not_empty = non-exhaustive patterns: type `{$ty}` is non-empty
-    .def_note = `{$peeled_ty}` defined here
-    .type_note = the matched value is of type `{$ty}`
-    .non_exhaustive_type_note = the matched value is of type `{$ty}`, which is marked as non-exhaustive
-    .reference_note = references are always considered inhabited
-    .suggestion = ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown
-    .help = ensure that all possible cases are being handled by adding a match arm with a wildcard pattern
-
-mir_build_static_in_pattern = statics cannot be referenced in patterns
-
-mir_build_assoc_const_in_pattern = associated consts cannot be referenced in patterns
-
-mir_build_const_param_in_pattern = const parameters cannot be referenced in patterns
+mir_build_extern_static_requires_unsafe =
+    use of extern static is unsafe and requires unsafe block
+    .note = extern statics are not controlled by the Rust type system: invalid data, aliasing violations or data races will cause undefined behavior
+    .label = use of extern static
 
-mir_build_non_const_path = runtime values cannot be referenced in patterns
+mir_build_extern_static_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
+    use of extern static is unsafe and requires unsafe function or block
+    .note = extern statics are not controlled by the Rust type system: invalid data, aliasing violations or data races will cause undefined behavior
+    .label = use of extern static
 
-mir_build_unreachable_pattern = unreachable pattern
-    .label = unreachable pattern
-    .catchall_label = matches any value
+mir_build_float_pattern = floating-point types cannot be used in patterns
 
-mir_build_const_pattern_depends_on_generic_parameter =
-    constant pattern depends on a generic parameter
+mir_build_indirect_structural_match =
+    to use a constant of type `{$non_sm_ty}` in a pattern, `{$non_sm_ty}` must be annotated with `#[derive(PartialEq, Eq)]`
 
-mir_build_could_not_eval_const_pattern = could not evaluate constant pattern
+mir_build_inform_irrefutable = `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
 
-mir_build_lower_range_bound_must_be_less_than_or_equal_to_upper =
-    lower range bound must be less than or equal to upper
-    .label = lower bound larger than upper bound
-    .teach_note = When matching against a range, the compiler verifies that the range is non-empty. Range patterns include both end-points, so this is equivalent to requiring the start of the range to be less than or equal to the end of the range.
+mir_build_initializing_type_with_requires_unsafe =
+    initializing type with `rustc_layout_scalar_valid_range` attr is unsafe and requires unsafe block
+    .note = initializing a layout restricted type's field with a value outside the valid range is undefined behavior
+    .label = initializing type with `rustc_layout_scalar_valid_range` attr
 
-mir_build_literal_in_range_out_of_bounds =
-    literal out of range for `{$ty}`
-    .label = this value doesn't fit in `{$ty}` whose maximum value is `{$max}`
+mir_build_initializing_type_with_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
+    initializing type with `rustc_layout_scalar_valid_range` attr is unsafe and requires unsafe function or block
+    .note = initializing a layout restricted type's field with a value outside the valid range is undefined behavior
+    .label = initializing type with `rustc_layout_scalar_valid_range` attr
 
-mir_build_lower_range_bound_must_be_less_than_upper = lower range bound must be less than upper
+mir_build_inline_assembly_requires_unsafe =
+    use of inline assembly is unsafe and requires unsafe block
+    .note = inline assembly is entirely unchecked and can cause undefined behavior
+    .label = use of inline assembly
 
-mir_build_leading_irrefutable_let_patterns = leading irrefutable {$count ->
-        [one] pattern
-        *[other] patterns
-    } in let chain
-    .note = {$count ->
-        [one] this pattern
-        *[other] these patterns
-    } will always match
-    .help = consider moving {$count ->
-        [one] it
-        *[other] them
-    } outside of the construct
+mir_build_inline_assembly_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
+    use of inline assembly is unsafe and requires unsafe function or block
+    .note = inline assembly is entirely unchecked and can cause undefined behavior
+    .label = use of inline assembly
 
-mir_build_trailing_irrefutable_let_patterns = trailing irrefutable {$count ->
-        [one] pattern
-        *[other] patterns
-    } in let chain
-    .note = {$count ->
-        [one] this pattern
-        *[other] these patterns
-    } will always match
-    .help = consider moving {$count ->
-        [one] it
-        *[other] them
-    } into the body
+mir_build_interpreted_as_const = introduce a variable instead
 
-mir_build_bindings_with_variant_name =
-    pattern binding `{$name}` is named the same as one of the variants of the type `{$ty_path}`
-    .suggestion = to match on the variant, qualify the path
+mir_build_invalid_pattern = `{$non_sm_ty}` cannot be used in patterns
 
 mir_build_irrefutable_let_patterns_if_let = irrefutable `if let` {$count ->
         [one] pattern
@@ -282,78 +158,97 @@ mir_build_irrefutable_let_patterns_while_let = irrefutable `while let` {$count -
     } will always match, so the loop will never exit
     .help = consider instead using a `loop {"{"} ... {"}"}` with a `let` inside it
 
-mir_build_borrow_of_moved_value = borrow of moved value
-    .label = value moved into `{$name}` here
-    .occurs_because_label = move occurs because `{$name}` has type `{$ty}` which does not implement the `Copy` trait
-    .value_borrowed_label = value borrowed here after move
-    .suggestion = borrow this binding in the pattern to avoid moving the value
+mir_build_leading_irrefutable_let_patterns = leading irrefutable {$count ->
+        [one] pattern
+        *[other] patterns
+    } in let chain
+    .note = {$count ->
+        [one] this pattern
+        *[other] these patterns
+    } will always match
+    .help = consider moving {$count ->
+        [one] it
+        *[other] them
+    } outside of the construct
 
-mir_build_multiple_mut_borrows = cannot borrow value as mutable more than once at a time
+mir_build_literal_in_range_out_of_bounds =
+    literal out of range for `{$ty}`
+    .label = this value doesn't fit in `{$ty}` whose maximum value is `{$max}`
 
-mir_build_already_borrowed = cannot borrow value as mutable because it is also borrowed as immutable
+mir_build_lower_range_bound_must_be_less_than_or_equal_to_upper =
+    lower range bound must be less than or equal to upper
+    .label = lower bound larger than upper bound
+    .teach_note = When matching against a range, the compiler verifies that the range is non-empty. Range patterns include both end-points, so this is equivalent to requiring the start of the range to be less than or equal to the end of the range.
 
-mir_build_already_mut_borrowed = cannot borrow value as immutable because it is also borrowed as mutable
+mir_build_lower_range_bound_must_be_less_than_upper = lower range bound must be less than upper
 
-mir_build_moved_while_borrowed = cannot move out of value because it is borrowed
+mir_build_more_information = for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
 
-mir_build_mutable_borrow = value is mutably borrowed by `{$name}` here
+mir_build_moved = value is moved into `{$name}` here
 
-mir_build_borrow = value is borrowed by `{$name}` here
+mir_build_moved_while_borrowed = cannot move out of value because it is borrowed
 
-mir_build_moved = value is moved into `{$name}` here
+mir_build_multiple_mut_borrows = cannot borrow value as mutable more than once at a time
 
-mir_build_union_pattern = cannot use unions in constant patterns
+mir_build_mutable_borrow = value is mutably borrowed by `{$name}` here
 
-mir_build_type_not_structural =
-     to use a constant of type `{$non_sm_ty}` in a pattern, `{$non_sm_ty}` must be annotated with `#[derive(PartialEq, Eq)]`
+mir_build_mutable_static_requires_unsafe =
+    use of mutable static is unsafe and requires unsafe block
+    .note = mutable statics can be mutated by multiple threads: aliasing violations or data races will cause undefined behavior
+    .label = use of mutable static
 
-mir_build_unsized_pattern = cannot use unsized non-slice type `{$non_sm_ty}` in constant patterns
+mir_build_mutable_static_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
+    use of mutable static is unsafe and requires unsafe function or block
+    .note = mutable statics can be mutated by multiple threads: aliasing violations or data races will cause undefined behavior
+    .label = use of mutable static
 
-mir_build_invalid_pattern = `{$non_sm_ty}` cannot be used in patterns
+mir_build_mutation_of_layout_constrained_field_requires_unsafe =
+    mutation of layout constrained field is unsafe and requires unsafe block
+    .note = mutating layout constrained fields cannot statically be checked for valid values
+    .label = mutation of layout constrained field
 
-mir_build_float_pattern = floating-point types cannot be used in patterns
+mir_build_mutation_of_layout_constrained_field_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
+    mutation of layout constrained field is unsafe and requires unsafe function or block
+    .note = mutating layout constrained fields cannot statically be checked for valid values
+    .label = mutation of layout constrained field
 
-mir_build_pointer_pattern = function pointers and unsized pointers in patterns behave unpredictably and should not be relied upon. See https://github.com/rust-lang/rust/issues/70861 for details.
+mir_build_non_const_path = runtime values cannot be referenced in patterns
 
-mir_build_indirect_structural_match =
-    to use a constant of type `{$non_sm_ty}` in a pattern, `{$non_sm_ty}` must be annotated with `#[derive(PartialEq, Eq)]`
+mir_build_non_exhaustive_omitted_pattern = some variants are not matched explicitly
+    .help = ensure that all variants are matched explicitly by adding the suggested match arms
+    .note = the matched value is of type `{$scrut_ty}` and the `non_exhaustive_omitted_patterns` attribute was found
+
+mir_build_non_exhaustive_patterns_type_not_empty = non-exhaustive patterns: type `{$ty}` is non-empty
+    .def_note = `{$peeled_ty}` defined here
+    .type_note = the matched value is of type `{$ty}`
+    .non_exhaustive_type_note = the matched value is of type `{$ty}`, which is marked as non-exhaustive
+    .reference_note = references are always considered inhabited
+    .suggestion = ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown
+    .help = ensure that all possible cases are being handled by adding a match arm with a wildcard pattern
 
 mir_build_nontrivial_structural_match =
     to use a constant of type `{$non_sm_ty}` in a pattern, the constant's initializer must be trivial or `{$non_sm_ty}` must be annotated with `#[derive(PartialEq, Eq)]`
 
-mir_build_type_not_structural_tip = the traits must be derived, manual `impl`s are not sufficient
-
-mir_build_type_not_structural_more_info = see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details
-
 mir_build_overlapping_range_endpoints = multiple patterns overlap on their endpoints
     .range = ... with this range
     .note = you likely meant to write mutually exclusive ranges
 
-mir_build_non_exhaustive_omitted_pattern = some variants are not matched explicitly
-    .help = ensure that all variants are matched explicitly by adding the suggested match arms
-    .note = the matched value is of type `{$scrut_ty}` and the `non_exhaustive_omitted_patterns` attribute was found
-
-mir_build_uncovered = {$count ->
-        [1] pattern `{$witness_1}`
-        [2] patterns `{$witness_1}` and `{$witness_2}`
-        [3] patterns `{$witness_1}`, `{$witness_2}` and `{$witness_3}`
-        *[other] patterns `{$witness_1}`, `{$witness_2}`, `{$witness_3}` and {$remainder} more
-    } not covered
-
 mir_build_pattern_not_covered = refutable pattern in {$origin}
     .pattern_ty = the matched value is of type `{$pattern_ty}`
 
-mir_build_inform_irrefutable = `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
+mir_build_pointer_pattern = function pointers and unsized pointers in patterns behave unpredictably and should not be relied upon. See https://github.com/rust-lang/rust/issues/70861 for details.
 
-mir_build_more_information = for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
+mir_build_privately_uninhabited = pattern `{$witness_1}` is currently uninhabited, but this variant contains private fields which may become inhabited in the future
 
-mir_build_adt_defined_here = `{$ty}` defined here
+mir_build_rustc_box_attribute_error = `#[rustc_box]` attribute used incorrectly
+    .attributes = no other attributes may be applied
+    .not_box = `#[rustc_box]` may only be applied to a `Box::new()` call
+    .missing_box = `#[rustc_box]` requires the `owned_box` lang item
 
-mir_build_variant_defined_here = not covered
+mir_build_static_in_pattern = statics cannot be referenced in patterns
 
-mir_build_interpreted_as_const = introduce a variable instead
+mir_build_suggest_attempted_int_lit = alternatively, you could prepend the pattern with an underscore to define a new named variable; identifiers cannot begin with digits
 
-mir_build_confused = missing patterns are not covered because `{$variable}` is interpreted as a constant pattern, not a new variable
 
 mir_build_suggest_if_let = you might want to use `if let` to ignore the {$count ->
         [one] variant that isn't
@@ -365,10 +260,117 @@ mir_build_suggest_let_else = you might want to use `let else` to handle the {$co
         *[other] variants that aren't
     } matched
 
-mir_build_suggest_attempted_int_lit = alternatively, you could prepend the pattern with an underscore to define a new named variable; identifiers cannot begin with digits
+mir_build_trailing_irrefutable_let_patterns = trailing irrefutable {$count ->
+        [one] pattern
+        *[other] patterns
+    } in let chain
+    .note = {$count ->
+        [one] this pattern
+        *[other] these patterns
+    } will always match
+    .help = consider moving {$count ->
+        [one] it
+        *[other] them
+    } into the body
+
+mir_build_type_not_structural =
+     to use a constant of type `{$non_sm_ty}` in a pattern, `{$non_sm_ty}` must be annotated with `#[derive(PartialEq, Eq)]`
 
+mir_build_type_not_structural_more_info = see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details
 
-mir_build_rustc_box_attribute_error = `#[rustc_box]` attribute used incorrectly
-    .attributes = no other attributes may be applied
-    .not_box = `#[rustc_box]` may only be applied to a `Box::new()` call
-    .missing_box = `#[rustc_box]` requires the `owned_box` lang item
+mir_build_type_not_structural_tip = the traits must be derived, manual `impl`s are not sufficient
+
+mir_build_unconditional_recursion = function cannot return without recursing
+    .label = cannot return without recursing
+    .help = a `loop` may express intention better if this is on purpose
+
+mir_build_unconditional_recursion_call_site_label = recursive call site
+
+mir_build_uncovered = {$count ->
+        [1] pattern `{$witness_1}`
+        [2] patterns `{$witness_1}` and `{$witness_2}`
+        [3] patterns `{$witness_1}`, `{$witness_2}` and `{$witness_3}`
+        *[other] patterns `{$witness_1}`, `{$witness_2}`, `{$witness_3}` and {$remainder} more
+    } not covered
+
+mir_build_union_field_requires_unsafe =
+    access to union field is unsafe and requires unsafe block
+    .note = the field may not be properly initialized: using uninitialized data will cause undefined behavior
+    .label = access to union field
+
+mir_build_union_field_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
+    access to union field is unsafe and requires unsafe function or block
+    .note = the field may not be properly initialized: using uninitialized data will cause undefined behavior
+    .label = access to union field
+
+mir_build_union_pattern = cannot use unions in constant patterns
+
+mir_build_unreachable_pattern = unreachable pattern
+    .label = unreachable pattern
+    .catchall_label = matches any value
+
+mir_build_unsafe_op_in_unsafe_fn_borrow_of_layout_constrained_field_requires_unsafe =
+    borrow of layout constrained field with interior mutability is unsafe and requires unsafe block (error E0133)
+    .note = references to fields of layout constrained fields lose the constraints. Coupled with interior mutability, the field can be changed to invalid values
+    .label = borrow of layout constrained field with interior mutability
+
+mir_build_unsafe_op_in_unsafe_fn_call_to_fn_with_requires_unsafe =
+    call to function `{$function}` with `#[target_feature]` is unsafe and requires unsafe block (error E0133)
+    .note = can only be called if the required target features are available
+    .label = call to function with `#[target_feature]`
+
+mir_build_unsafe_op_in_unsafe_fn_call_to_unsafe_fn_requires_unsafe =
+    call to unsafe function `{$function}` is unsafe and requires unsafe block (error E0133)
+    .note = consult the function's documentation for information on how to avoid undefined behavior
+    .label = call to unsafe function
+
+mir_build_unsafe_op_in_unsafe_fn_call_to_unsafe_fn_requires_unsafe_nameless =
+    call to unsafe function is unsafe and requires unsafe block (error E0133)
+    .note = consult the function's documentation for information on how to avoid undefined behavior
+    .label = call to unsafe function
+
+mir_build_unsafe_op_in_unsafe_fn_deref_raw_pointer_requires_unsafe =
+    dereference of raw pointer is unsafe and requires unsafe block (error E0133)
+    .note = raw pointers may be null, dangling or unaligned; they can violate aliasing rules and cause data races: all of these are undefined behavior
+    .label = dereference of raw pointer
+
+mir_build_unsafe_op_in_unsafe_fn_extern_static_requires_unsafe =
+    use of extern static is unsafe and requires unsafe block (error E0133)
+    .note = extern statics are not controlled by the Rust type system: invalid data, aliasing violations or data races will cause undefined behavior
+    .label = use of extern static
+
+mir_build_unsafe_op_in_unsafe_fn_initializing_type_with_requires_unsafe =
+    initializing type with `rustc_layout_scalar_valid_range` attr is unsafe and requires unsafe
+    block (error E0133)
+    .note = initializing a layout restricted type's field with a value outside the valid range is undefined behavior
+    .label = initializing type with `rustc_layout_scalar_valid_range` attr
+
+mir_build_unsafe_op_in_unsafe_fn_inline_assembly_requires_unsafe =
+    use of inline assembly is unsafe and requires unsafe block (error E0133)
+    .note = inline assembly is entirely unchecked and can cause undefined behavior
+    .label = use of inline assembly
+
+mir_build_unsafe_op_in_unsafe_fn_mutable_static_requires_unsafe =
+    use of mutable static is unsafe and requires unsafe block (error E0133)
+    .note = mutable statics can be mutated by multiple threads: aliasing violations or data races will cause undefined behavior
+    .label = use of mutable static
+
+mir_build_unsafe_op_in_unsafe_fn_mutation_of_layout_constrained_field_requires_unsafe =
+    mutation of layout constrained field is unsafe and requires unsafe block (error E0133)
+    .note = mutating layout constrained fields cannot statically be checked for valid values
+    .label = mutation of layout constrained field
+
+mir_build_unsafe_op_in_unsafe_fn_union_field_requires_unsafe =
+    access to union field is unsafe and requires unsafe block (error E0133)
+    .note = the field may not be properly initialized: using uninitialized data will cause undefined behavior
+    .label = access to union field
+
+mir_build_unsized_pattern = cannot use unsized non-slice type `{$non_sm_ty}` in constant patterns
+
+mir_build_unused_unsafe = unnecessary `unsafe` block
+    .label = unnecessary `unsafe` block
+
+mir_build_unused_unsafe_enclosing_block_label = because it's nested under this `unsafe` block
+mir_build_unused_unsafe_enclosing_fn_label = because it's nested under this `unsafe` fn
+
+mir_build_variant_defined_here = not covered
diff --git a/compiler/rustc_mir_build/src/build/block.rs b/compiler/rustc_mir_build/src/build/block.rs
index 609ab1928..ab4cd2488 100644
--- a/compiler/rustc_mir_build/src/build/block.rs
+++ b/compiler/rustc_mir_build/src/build/block.rs
@@ -351,7 +351,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             }
 
             let popped = this.block_context.pop();
-            assert!(popped.map_or(false, |bf| bf.is_statement()));
+            assert!(popped.is_some_and(|bf| bf.is_statement()));
         }
 
         // Then, the block may have an optional trailing expression which is a “return” value
@@ -367,7 +367,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             unpack!(block = this.expr_into_dest(destination, block, expr));
             let popped = this.block_context.pop();
 
-            assert!(popped.map_or(false, |bf| bf.is_tail_expr()));
+            assert!(popped.is_some_and(|bf| bf.is_tail_expr()));
         } else {
             // If a block has no trailing expression, then it is given an implicit return type.
             // This return type is usually `()`, unless the block is diverging, in which case the
diff --git a/compiler/rustc_mir_build/src/build/custom/mod.rs b/compiler/rustc_mir_build/src/build/custom/mod.rs
index d385153ba..32c618828 100644
--- a/compiler/rustc_mir_build/src/build/custom/mod.rs
+++ b/compiler/rustc_mir_build/src/build/custom/mod.rs
@@ -21,7 +21,7 @@ use rustc_ast::Attribute;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def_id::DefId;
 use rustc_hir::HirId;
-use rustc_index::vec::{IndexSlice, IndexVec};
+use rustc_index::{IndexSlice, IndexVec};
 use rustc_middle::{
     mir::*,
     thir::*,
diff --git a/compiler/rustc_mir_build/src/build/custom/parse.rs b/compiler/rustc_mir_build/src/build/custom/parse.rs
index 12b2f5d80..803207d9d 100644
--- a/compiler/rustc_mir_build/src/build/custom/parse.rs
+++ b/compiler/rustc_mir_build/src/build/custom/parse.rs
@@ -1,4 +1,4 @@
-use rustc_index::vec::IndexSlice;
+use rustc_index::IndexSlice;
 use rustc_middle::{mir::*, thir::*, ty::Ty};
 use rustc_span::Span;
 
diff --git a/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs b/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs
index 931fe1b24..ebf830cb9 100644
--- a/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs
+++ b/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs
@@ -57,6 +57,7 @@ impl<'tcx, 'body> ParseCtxt<'tcx, 'body> {
                     place: self.parse_place(args[0])?,
                     target: self.parse_block(args[1])?,
                     unwind: UnwindAction::Continue,
+                    replace: false,
                 })
             },
             @call("mir_call", args) => {
@@ -154,6 +155,7 @@ impl<'tcx, 'body> ParseCtxt<'tcx, 'body> {
                 Ok(Rvalue::BinaryOp(BinOp::Offset, Box::new((ptr, offset))))
             },
             @call("mir_len", args) => Ok(Rvalue::Len(self.parse_place(args[0])?)),
+            @call("mir_copy_for_deref", args) => Ok(Rvalue::CopyForDeref(self.parse_place(args[0])?)),
             ExprKind::Borrow { borrow_kind, arg } => Ok(
                 Rvalue::Ref(self.tcx.lifetimes.re_erased, *borrow_kind, self.parse_place(*arg)?)
             ),
diff --git a/compiler/rustc_mir_build/src/build/expr/as_constant.rs b/compiler/rustc_mir_build/src/build/expr/as_constant.rs
index 99291740a..4d99ab4b0 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_constant.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_constant.rs
@@ -52,7 +52,7 @@ pub fn as_constant_inner<'tcx>(
                 match lit_to_mir_constant(tcx, LitToConstInput { lit: &lit.node, ty, neg }) {
                     Ok(c) => c,
                     Err(LitToConstError::Reported(guar)) => {
-                        ConstantKind::Ty(tcx.const_error_with_guaranteed(ty, guar))
+                        ConstantKind::Ty(tcx.const_error(ty, guar))
                     }
                     Err(LitToConstError::TypeError) => {
                         bug!("encountered type error in `lit_to_mir_constant`")
@@ -78,7 +78,7 @@ pub fn as_constant_inner<'tcx>(
         ExprKind::NamedConst { def_id, substs, ref user_ty } => {
             let user_ty = user_ty.as_ref().and_then(push_cuta);
 
-            let uneval = mir::UnevaluatedConst::new(ty::WithOptConstParam::unknown(def_id), substs);
+            let uneval = mir::UnevaluatedConst::new(def_id, substs);
             let literal = ConstantKind::Unevaluated(uneval, ty);
 
             Constant { user_ty, span, literal }
@@ -90,7 +90,7 @@ pub fn as_constant_inner<'tcx>(
             Constant { user_ty: None, span, literal }
         }
         ExprKind::ConstBlock { did: def_id, substs } => {
-            let uneval = mir::UnevaluatedConst::new(ty::WithOptConstParam::unknown(def_id), substs);
+            let uneval = mir::UnevaluatedConst::new(def_id, substs);
             let literal = ConstantKind::Unevaluated(uneval, ty);
 
             Constant { user_ty: None, span, literal }
@@ -146,6 +146,12 @@ pub(crate) fn lit_to_mir_constant<'tcx>(
             let id = tcx.allocate_bytes(data);
             ConstValue::Scalar(Scalar::from_pointer(id.into(), &tcx))
         }
+        (ast::LitKind::CStr(data, _), ty::Ref(_, inner_ty, _)) if matches!(inner_ty.kind(), ty::Adt(def, _) if Some(def.did()) == tcx.lang_items().c_str()) =>
+        {
+            let allocation = Allocation::from_bytes_byte_aligned_immutable(data as &[u8]);
+            let allocation = tcx.mk_const_alloc(allocation);
+            ConstValue::Slice { data: allocation, start: 0, end: data.len() }
+        }
         (ast::LitKind::Byte(n), ty::Uint(ty::UintTy::U8)) => {
             ConstValue::Scalar(Scalar::from_uint(*n, Size::from_bytes(1)))
         }
diff --git a/compiler/rustc_mir_build/src/build/expr/as_operand.rs b/compiler/rustc_mir_build/src/build/expr/as_operand.rs
index 6941da331..744111edb 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_operand.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_operand.rs
@@ -118,7 +118,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         let category = Category::of(&expr.kind).unwrap();
         debug!(?category, ?expr.kind);
         match category {
-            Category::Constant if let NeedsTemporary::No = needs_temporary || !expr.ty.needs_drop(this.tcx, this.param_env) => {
+            Category::Constant
+                if matches!(needs_temporary, NeedsTemporary::No)
+                    || !expr.ty.needs_drop(this.tcx, this.param_env) =>
+            {
                 let constant = this.as_constant(expr);
                 block.and(Operand::Constant(Box::new(constant)))
             }
@@ -126,7 +129,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 let operand = unpack!(block = this.as_temp(block, scope, expr, Mutability::Mut));
                 // Overwrite temp local info if we have something more interesting to record.
                 if !matches!(local_info, LocalInfo::Boring) {
-                    let decl_info = this.local_decls[operand].local_info.as_mut().assert_crate_local();
+                    let decl_info =
+                        this.local_decls[operand].local_info.as_mut().assert_crate_local();
                     if let LocalInfo::Boring | LocalInfo::BlockTailTemp(_) = **decl_info {
                         **decl_info = local_info;
                     }
diff --git a/compiler/rustc_mir_build/src/build/expr/as_place.rs b/compiler/rustc_mir_build/src/build/expr/as_place.rs
index fb775766c..7ec57add6 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_place.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_place.rs
@@ -557,6 +557,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             | ExprKind::ConstBlock { .. }
             | ExprKind::StaticRef { .. }
             | ExprKind::InlineAsm { .. }
+            | ExprKind::OffsetOf { .. }
             | ExprKind::Yield { .. }
             | ExprKind::ThreadLocalRef(_)
             | ExprKind::Call { .. } => {
diff --git a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs b/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
index 8631749a5..3742d640e 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
@@ -1,6 +1,6 @@
 //! See docs in `build/expr/mod.rs`.
 
-use rustc_index::vec::{Idx, IndexVec};
+use rustc_index::{Idx, IndexVec};
 use rustc_middle::ty::util::IntTypeExt;
 use rustc_target::abi::{Abi, FieldIdx, Primitive};
 
@@ -15,6 +15,7 @@ use rustc_middle::mir::Place;
 use rustc_middle::mir::*;
 use rustc_middle::thir::*;
 use rustc_middle::ty::cast::{mir_cast_kind, CastTy};
+use rustc_middle::ty::layout::IntegerExt;
 use rustc_middle::ty::{self, Ty, UpvarSubsts};
 use rustc_span::Span;
 
@@ -225,49 +226,63 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     );
                     let (op,ty) = (Operand::Move(discr), discr_ty);
 
-                    if let Abi::Scalar(scalar) = layout.unwrap().abi{
-                        if let Primitive::Int(_, signed) = scalar.primitive() {
-                            let range = scalar.valid_range(&this.tcx);
-                            // FIXME: Handle wraparound cases too.
-                            if range.end >= range.start {
-                                let mut assumer = |range: u128, bin_op: BinOp| {
-                                    // We will be overwriting this val if our scalar is signed value
-                                    // because sign extension on unsigned types might cause unintended things
-                                    let mut range_val =
-                                        ConstantKind::from_bits(this.tcx, range, ty::ParamEnv::empty().and(discr_ty));
-                                    let bool_ty = this.tcx.types.bool;
-                                    if signed {
-                                        let scalar_size_extend = scalar.size(&this.tcx).sign_extend(range);
-                                        let discr_layout = this.tcx.layout_of(this.param_env.and(discr_ty));
-                                        let truncated_val = discr_layout.unwrap().size.truncate(scalar_size_extend);
-                                        range_val = ConstantKind::from_bits(
-                                            this.tcx,
-                                            truncated_val,
-                                            ty::ParamEnv::empty().and(discr_ty),
-                                        );
-                                    }
-                                    let lit_op = this.literal_operand(expr.span, range_val);
-                                    let is_bin_op = this.temp(bool_ty, expr_span);
-                                    this.cfg.push_assign(
-                                        block,
-                                        source_info,
-                                        is_bin_op,
-                                        Rvalue::BinaryOp(bin_op, Box::new(((lit_op), (Operand::Copy(discr))))),
-                                    );
-                                    this.cfg.push(
-                                        block,
-                                        Statement {
-                                            source_info,
-                                            kind: StatementKind::Intrinsic(Box::new(NonDivergingIntrinsic::Assume(
-                                                Operand::Copy(is_bin_op),
-                                            ))),
-                                        },
-                                    )
-                                };
-                                assumer(range.end, BinOp::Ge);
-                                assumer(range.start, BinOp::Le);
-                            }
-                        }
+                    if let Abi::Scalar(scalar) = layout.unwrap().abi
+                        && !scalar.is_always_valid(&this.tcx)
+                        && let Primitive::Int(int_width, _signed) = scalar.primitive()
+                    {
+                        let unsigned_ty = int_width.to_ty(this.tcx, false);
+                        let unsigned_place = this.temp(unsigned_ty, expr_span);
+                        this.cfg.push_assign(
+                            block,
+                            source_info,
+                            unsigned_place,
+                            Rvalue::Cast(CastKind::IntToInt, Operand::Copy(discr), unsigned_ty));
+
+                        let bool_ty = this.tcx.types.bool;
+                        let range = scalar.valid_range(&this.tcx);
+                        let merge_op =
+                            if range.start <= range.end {
+                                BinOp::BitAnd
+                            } else {
+                                BinOp::BitOr
+                            };
+
+                        let mut comparer = |range: u128, bin_op: BinOp| -> Place<'tcx> {
+                            let range_val =
+                                ConstantKind::from_bits(this.tcx, range, ty::ParamEnv::empty().and(unsigned_ty));
+                            let lit_op = this.literal_operand(expr.span, range_val);
+                            let is_bin_op = this.temp(bool_ty, expr_span);
+                            this.cfg.push_assign(
+                                block,
+                                source_info,
+                                is_bin_op,
+                                Rvalue::BinaryOp(bin_op, Box::new((Operand::Copy(unsigned_place), lit_op))),
+                            );
+                            is_bin_op
+                        };
+                        let assert_place = if range.start == 0 {
+                            comparer(range.end, BinOp::Le)
+                        } else {
+                            let start_place = comparer(range.start, BinOp::Ge);
+                            let end_place = comparer(range.end, BinOp::Le);
+                            let merge_place = this.temp(bool_ty, expr_span);
+                            this.cfg.push_assign(
+                                block,
+                                source_info,
+                                merge_place,
+                                Rvalue::BinaryOp(merge_op, Box::new((Operand::Move(start_place), Operand::Move(end_place)))),
+                            );
+                            merge_place
+                        };
+                        this.cfg.push(
+                            block,
+                            Statement {
+                                source_info,
+                                kind: StatementKind::Intrinsic(Box::new(NonDivergingIntrinsic::Assume(
+                                    Operand::Move(assert_place),
+                                ))),
+                            },
+                        );
                     }
 
                     (op,ty)
@@ -481,6 +496,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 }))))
             }
 
+            ExprKind::OffsetOf { container, fields } => {
+                block.and(Rvalue::NullaryOp(NullOp::OffsetOf(fields), container))
+            }
+
             ExprKind::Literal { .. }
             | ExprKind::NamedConst { .. }
             | ExprKind::NonHirLiteral { .. }
@@ -706,6 +725,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         place: to_drop,
                         target: success,
                         unwind: UnwindAction::Continue,
+                        replace: false,
                     },
                 );
                 this.diverge_from(block);
diff --git a/compiler/rustc_mir_build/src/build/expr/category.rs b/compiler/rustc_mir_build/src/build/expr/category.rs
index d33401f07..d9aa461c1 100644
--- a/compiler/rustc_mir_build/src/build/expr/category.rs
+++ b/compiler/rustc_mir_build/src/build/expr/category.rs
@@ -67,7 +67,8 @@ impl Category {
             | ExprKind::Repeat { .. }
             | ExprKind::Assign { .. }
             | ExprKind::AssignOp { .. }
-            | ExprKind::ThreadLocalRef(_) => Some(Category::Rvalue(RvalueFunc::AsRvalue)),
+            | ExprKind::ThreadLocalRef(_)
+            | ExprKind::OffsetOf { .. } => Some(Category::Rvalue(RvalueFunc::AsRvalue)),
 
             ExprKind::ConstBlock { .. }
             | ExprKind::Literal { .. }
diff --git a/compiler/rustc_mir_build/src/build/expr/into.rs b/compiler/rustc_mir_build/src/build/expr/into.rs
index 05a723a6b..29ff916d2 100644
--- a/compiler/rustc_mir_build/src/build/expr/into.rs
+++ b/compiler/rustc_mir_build/src/build/expr/into.rs
@@ -163,13 +163,13 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 //
                 // [block: If(lhs)] -true-> [else_block: dest = (rhs)]
                 //        | (false)
-                //  [shortcurcuit_block: dest = false]
+                //  [shortcircuit_block: dest = false]
                 //
                 // Or:
                 //
                 // [block: If(lhs)] -false-> [else_block: dest = (rhs)]
                 //        | (true)
-                //  [shortcurcuit_block: dest = true]
+                //  [shortcircuit_block: dest = true]
 
                 let (shortcircuit_block, mut else_block, join_block) = (
                     this.cfg.start_new_block(),
@@ -561,7 +561,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             | ExprKind::ZstLiteral { .. }
             | ExprKind::ConstParam { .. }
             | ExprKind::ThreadLocalRef(_)
-            | ExprKind::StaticRef { .. } => {
+            | ExprKind::StaticRef { .. }
+            | ExprKind::OffsetOf { .. } => {
                 debug_assert!(match Category::of(&expr.kind).unwrap() {
                     // should be handled above
                     Category::Rvalue(RvalueFunc::Into) => false,
diff --git a/compiler/rustc_mir_build/src/build/matches/mod.rs b/compiler/rustc_mir_build/src/build/matches/mod.rs
index 4926ff85d..6df06df5c 100644
--- a/compiler/rustc_mir_build/src/build/matches/mod.rs
+++ b/compiler/rustc_mir_build/src/build/matches/mod.rs
@@ -2241,6 +2241,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         self.var_debug_info.push(VarDebugInfo {
             name,
             source_info: debug_source_info,
+            references: 0,
             value: VarDebugInfoContents::Place(for_arm_body.into()),
             argument_index: None,
         });
@@ -2260,6 +2261,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             self.var_debug_info.push(VarDebugInfo {
                 name,
                 source_info: debug_source_info,
+                references: 0,
                 value: VarDebugInfoContents::Place(ref_for_guard.into()),
                 argument_index: None,
             });
diff --git a/compiler/rustc_mir_build/src/build/matches/test.rs b/compiler/rustc_mir_build/src/build/matches/test.rs
index 8a03ea7e2..dbdb5b4a9 100644
--- a/compiler/rustc_mir_build/src/build/matches/test.rs
+++ b/compiler/rustc_mir_build/src/build/matches/test.rs
@@ -77,7 +77,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             | PatKind::Wild
             | PatKind::Binding { .. }
             | PatKind::Leaf { .. }
-            | PatKind::Deref { .. } => self.error_simplifyable(match_pair),
+            | PatKind::Deref { .. } => self.error_simplifiable(match_pair),
         }
     }
 
@@ -173,7 +173,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                             debug_assert_ne!(
                                 target_blocks[idx.index()],
                                 otherwise_block,
-                                "no canididates for tested discriminant: {:?}",
+                                "no candidates for tested discriminant: {:?}",
                                 discr,
                             );
                             Some((discr.val, target_blocks[idx.index()]))
@@ -181,7 +181,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                             debug_assert_eq!(
                                 target_blocks[idx.index()],
                                 otherwise_block,
-                                "found canididates for untested discriminant: {:?}",
+                                "found candidates for untested discriminant: {:?}",
                                 discr,
                             );
                             None
@@ -380,18 +380,19 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         );
     }
 
-    /// Compare two `&T` values using `<T as std::compare::PartialEq>::eq`
+    /// Compare two values using `<T as std::compare::PartialEq>::eq`.
+    /// If the values are already references, just call it directly, otherwise
+    /// take a reference to the values first and then call it.
     fn non_scalar_compare(
         &mut self,
         block: BasicBlock,
         make_target_blocks: impl FnOnce(&mut Self) -> Vec<BasicBlock>,
         source_info: SourceInfo,
         value: ConstantKind<'tcx>,
-        place: Place<'tcx>,
+        mut val: Place<'tcx>,
         mut ty: Ty<'tcx>,
     ) {
         let mut expect = self.literal_operand(source_info.span, value);
-        let mut val = Operand::Copy(place);
 
         // If we're using `b"..."` as a pattern, we need to insert an
         // unsizing coercion, as the byte string has the type `&[u8; N]`.
@@ -421,9 +422,13 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         block,
                         source_info,
                         temp,
-                        Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), val, ty),
+                        Rvalue::Cast(
+                            CastKind::Pointer(PointerCast::Unsize),
+                            Operand::Copy(val),
+                            ty,
+                        ),
                     );
-                    val = Operand::Move(temp);
+                    val = temp;
                 }
                 if opt_ref_test_ty.is_some() {
                     let slice = self.temp(ty, source_info.span);
@@ -438,12 +443,36 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             }
         }
 
-        let ty::Ref(_, deref_ty, _) = *ty.kind() else {
-            bug!("non_scalar_compare called on non-reference type: {}", ty);
-        };
+        match *ty.kind() {
+            ty::Ref(_, deref_ty, _) => ty = deref_ty,
+            _ => {
+                // non_scalar_compare called on non-reference type
+                let temp = self.temp(ty, source_info.span);
+                self.cfg.push_assign(block, source_info, temp, Rvalue::Use(expect));
+                let ref_ty = self.tcx.mk_imm_ref(self.tcx.lifetimes.re_erased, ty);
+                let ref_temp = self.temp(ref_ty, source_info.span);
+
+                self.cfg.push_assign(
+                    block,
+                    source_info,
+                    ref_temp,
+                    Rvalue::Ref(self.tcx.lifetimes.re_erased, BorrowKind::Shared, temp),
+                );
+                expect = Operand::Move(ref_temp);
+
+                let ref_temp = self.temp(ref_ty, source_info.span);
+                self.cfg.push_assign(
+                    block,
+                    source_info,
+                    ref_temp,
+                    Rvalue::Ref(self.tcx.lifetimes.re_erased, BorrowKind::Shared, val),
+                );
+                val = ref_temp;
+            }
+        }
 
         let eq_def_id = self.tcx.require_lang_item(LangItem::PartialEq, Some(source_info.span));
-        let method = trait_method(self.tcx, eq_def_id, sym::eq, [deref_ty, deref_ty]);
+        let method = trait_method(self.tcx, eq_def_id, sym::eq, [ty, ty]);
 
         let bool_ty = self.tcx.types.bool;
         let eq_result = self.temp(bool_ty, source_info.span);
@@ -463,7 +492,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
                     literal: method,
                 })),
-                args: vec![val, expect],
+                args: vec![Operand::Copy(val), expect],
                 destination: eq_result,
                 target: Some(eq_block),
                 unwind: UnwindAction::Continue,
@@ -499,7 +528,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// However, in some cases, the test may just not be relevant to candidate.
     /// For example, suppose we are testing whether `foo.x == 22`, but in one
     /// match arm we have `Foo { x: _, ... }`... in that case, the test for
-    /// what value `x` has has no particular relevance to this candidate. In
+    /// the value of `x` has no particular relevance to this candidate. In
     /// such cases, this function just returns None without doing anything.
     /// This is used by the overall `match_candidates` algorithm to structure
     /// the match as a whole. See `match_candidates` for more details.
@@ -763,8 +792,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         candidate.match_pairs.extend(consequent_match_pairs);
     }
 
-    fn error_simplifyable<'pat>(&mut self, match_pair: &MatchPair<'pat, 'tcx>) -> ! {
-        span_bug!(match_pair.pattern.span, "simplifyable pattern found: {:?}", match_pair.pattern)
+    fn error_simplifiable<'pat>(&mut self, match_pair: &MatchPair<'pat, 'tcx>) -> ! {
+        span_bug!(match_pair.pattern.span, "simplifiable pattern found: {:?}", match_pair.pattern)
     }
 
     fn const_range_contains(
diff --git a/compiler/rustc_mir_build/src/build/mod.rs b/compiler/rustc_mir_build/src/build/mod.rs
index bc50bcbc3..4e3e98b56 100644
--- a/compiler/rustc_mir_build/src/build/mod.rs
+++ b/compiler/rustc_mir_build/src/build/mod.rs
@@ -11,7 +11,7 @@ use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::{GeneratorKind, Node};
-use rustc_index::vec::{Idx, IndexSlice, IndexVec};
+use rustc_index::{Idx, IndexSlice, IndexVec};
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_middle::hir::place::PlaceBase as HirPlaceBase;
 use rustc_middle::middle::region;
@@ -32,43 +32,34 @@ use super::lints;
 
 pub(crate) fn mir_built(
     tcx: TyCtxt<'_>,
-    def: ty::WithOptConstParam<LocalDefId>,
+    def: LocalDefId,
 ) -> &rustc_data_structures::steal::Steal<Body<'_>> {
-    if let Some(def) = def.try_upgrade(tcx) {
-        return tcx.mir_built(def);
-    }
-
-    let mut body = mir_build(tcx, def);
-    if def.const_param_did.is_some() {
-        assert!(matches!(body.source.instance, ty::InstanceDef::Item(_)));
-        body.source = MirSource::from_instance(ty::InstanceDef::Item(def.to_global()));
-    }
-
-    tcx.alloc_steal_mir(body)
+    tcx.alloc_steal_mir(mir_build(tcx, def))
 }
 
 /// Construct the MIR for a given `DefId`.
-fn mir_build(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> Body<'_> {
+fn mir_build(tcx: TyCtxt<'_>, def: LocalDefId) -> Body<'_> {
     // Ensure unsafeck and abstract const building is ran before we steal the THIR.
-    match def {
-        ty::WithOptConstParam { did, const_param_did: Some(const_param_did) } => {
-            tcx.ensure_with_value().thir_check_unsafety_for_const_arg((did, const_param_did));
-            tcx.ensure_with_value().thir_abstract_const_of_const_arg((did, const_param_did));
-        }
-        ty::WithOptConstParam { did, const_param_did: None } => {
-            tcx.ensure_with_value().thir_check_unsafety(did);
-            tcx.ensure_with_value().thir_abstract_const(did);
-            tcx.ensure_with_value().check_match(did);
-        }
+    tcx.ensure_with_value().thir_check_unsafety(def);
+    tcx.ensure_with_value().thir_abstract_const(def);
+    if let Err(e) = tcx.check_match(def) {
+        return construct_error(tcx, def, e);
     }
 
     let body = match tcx.thir_body(def) {
-        Err(error_reported) => construct_error(tcx, def.did, error_reported),
+        Err(error_reported) => construct_error(tcx, def, error_reported),
         Ok((thir, expr)) => {
             // We ran all queries that depended on THIR at the beginning
             // of `mir_build`, so now we can steal it
             let thir = thir.steal();
 
+            tcx.ensure().check_match(def);
+            // this must run before MIR dump, because
+            // "not all control paths return a value" is reported here.
+            //
+            // maybe move the check to a MIR pass?
+            tcx.ensure().check_liveness(def);
+
             match thir.body_type {
                 thir::BodyTy::Fn(fn_sig) => construct_fn(tcx, def, &thir, expr, fn_sig),
                 thir::BodyTy::Const(ty) => construct_const(tcx, def, &thir, expr, ty),
@@ -161,8 +152,7 @@ struct Builder<'a, 'tcx> {
     thir: &'a Thir<'tcx>,
     cfg: CFG<'tcx>,
 
-    def: ty::WithOptConstParam<LocalDefId>,
-    def_id: DefId,
+    def_id: LocalDefId,
     hir_id: hir::HirId,
     parent_module: DefId,
     check_overflow: bool,
@@ -428,26 +418,26 @@ macro_rules! unpack {
 
 fn construct_fn<'tcx>(
     tcx: TyCtxt<'tcx>,
-    fn_def: ty::WithOptConstParam<LocalDefId>,
+    fn_def: LocalDefId,
     thir: &Thir<'tcx>,
     expr: ExprId,
     fn_sig: ty::FnSig<'tcx>,
 ) -> Body<'tcx> {
-    let span = tcx.def_span(fn_def.did);
-    let fn_id = tcx.hir().local_def_id_to_hir_id(fn_def.did);
-    let generator_kind = tcx.generator_kind(fn_def.did);
+    let span = tcx.def_span(fn_def);
+    let fn_id = tcx.hir().local_def_id_to_hir_id(fn_def);
+    let generator_kind = tcx.generator_kind(fn_def);
 
     // The representation of thir for `-Zunpretty=thir-tree` relies on
     // the entry expression being the last element of `thir.exprs`.
     assert_eq!(expr.as_usize(), thir.exprs.len() - 1);
 
     // Figure out what primary body this item has.
-    let body_id = tcx.hir().body_owned_by(fn_def.did);
+    let body_id = tcx.hir().body_owned_by(fn_def);
     let span_with_body = tcx.hir().span_with_body(fn_id);
     let return_ty_span = tcx
         .hir()
         .fn_decl_by_hir_id(fn_id)
-        .unwrap_or_else(|| span_bug!(span, "can't build MIR for {:?}", fn_def.did))
+        .unwrap_or_else(|| span_bug!(span, "can't build MIR for {:?}", fn_def))
         .output
         .span();
 
@@ -457,7 +447,7 @@ fn construct_fn<'tcx>(
     };
 
     let mut abi = fn_sig.abi;
-    if let DefKind::Closure = tcx.def_kind(fn_def.did) {
+    if let DefKind::Closure = tcx.def_kind(fn_def) {
         // HACK(eddyb) Avoid having RustCall on closures,
         // as it adds unnecessary (and wrong) auto-tupling.
         abi = Abi::Rust;
@@ -483,7 +473,7 @@ fn construct_fn<'tcx>(
     {
         return custom::build_custom_mir(
             tcx,
-            fn_def.did.to_def_id(),
+            fn_def.to_def_id(),
             fn_id,
             thir,
             expr,
@@ -547,12 +537,12 @@ fn construct_fn<'tcx>(
 
 fn construct_const<'a, 'tcx>(
     tcx: TyCtxt<'tcx>,
-    def: ty::WithOptConstParam<LocalDefId>,
+    def: LocalDefId,
     thir: &'a Thir<'tcx>,
     expr: ExprId,
     const_ty: Ty<'tcx>,
 ) -> Body<'tcx> {
-    let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
+    let hir_id = tcx.hir().local_def_id_to_hir_id(def);
 
     // Figure out what primary body this item has.
     let (span, const_ty_span) = match tcx.hir().get(hir_id) {
@@ -568,10 +558,10 @@ fn construct_const<'a, 'tcx>(
             ..
         }) => (*span, ty.span),
         Node::AnonConst(_) => {
-            let span = tcx.def_span(def.did);
+            let span = tcx.def_span(def);
             (span, span)
         }
-        _ => span_bug!(tcx.def_span(def.did), "can't build MIR for {:?}", def.did),
+        _ => span_bug!(tcx.def_span(def), "can't build MIR for {:?}", def),
     };
 
     let infcx = tcx.infer_ctxt().build();
@@ -669,7 +659,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     fn new(
         thir: &'a Thir<'tcx>,
         infcx: InferCtxt<'tcx>,
-        def: ty::WithOptConstParam<LocalDefId>,
+        def: LocalDefId,
         hir_id: hir::HirId,
         span: Span,
         arg_count: usize,
@@ -688,20 +678,19 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         check_overflow |= tcx.sess.overflow_checks();
         // Constants always need overflow checks.
         check_overflow |= matches!(
-            tcx.hir().body_owner_kind(def.did),
+            tcx.hir().body_owner_kind(def),
             hir::BodyOwnerKind::Const | hir::BodyOwnerKind::Static(_)
         );
 
         let lint_level = LintLevel::Explicit(hir_id);
-        let param_env = tcx.param_env(def.did);
+        let param_env = tcx.param_env(def);
         let mut builder = Builder {
             thir,
             tcx,
             infcx,
-            region_scope_tree: tcx.region_scope_tree(def.did),
+            region_scope_tree: tcx.region_scope_tree(def),
             param_env,
-            def,
-            def_id: def.did.to_def_id(),
+            def_id: def,
             hir_id,
             parent_module: tcx.parent_module(hir_id).to_def_id(),
             check_overflow,
@@ -741,7 +730,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         }
 
         Body::new(
-            MirSource::item(self.def_id),
+            MirSource::item(self.def_id.to_def_id()),
             self.cfg.basic_blocks,
             self.source_scopes,
             self.local_decls,
@@ -779,7 +768,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
         let tcx = self.tcx;
         self.upvars = tcx
-            .closure_captures(self.def.did)
+            .closure_captures(self.def_id)
             .iter()
             .zip(capture_tys)
             .enumerate()
@@ -809,6 +798,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 };
                 self.var_debug_info.push(VarDebugInfo {
                     name,
+                    references: 0,
                     source_info: SourceInfo::outermost(captured_place.var_ident.span),
                     value: VarDebugInfoContents::Place(use_place),
                     argument_index: None,
@@ -839,6 +829,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 self.var_debug_info.push(VarDebugInfo {
                     name,
                     source_info,
+                    references: 0,
                     value: VarDebugInfoContents::Place(arg_local.into()),
                     argument_index: Some(argument_index as u16 + 1),
                 });
diff --git a/compiler/rustc_mir_build/src/build/scope.rs b/compiler/rustc_mir_build/src/build/scope.rs
index f32d2db4e..7c0fbc6f8 100644
--- a/compiler/rustc_mir_build/src/build/scope.rs
+++ b/compiler/rustc_mir_build/src/build/scope.rs
@@ -86,12 +86,12 @@ use std::mem;
 use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder, CFG};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::HirId;
-use rustc_index::vec::{IndexSlice, IndexVec};
+use rustc_index::{IndexSlice, IndexVec};
 use rustc_middle::middle::region;
 use rustc_middle::mir::*;
 use rustc_middle::thir::{Expr, LintLevel};
 
-use rustc_span::{DesugaringKind, Span, DUMMY_SP};
+use rustc_span::{Span, DUMMY_SP};
 
 #[derive(Debug)]
 pub struct Scopes<'tcx> {
@@ -325,10 +325,10 @@ impl DropTree {
         entry_points.sort();
 
         for (drop_idx, drop_data) in self.drops.iter_enumerated().rev() {
-            if entry_points.last().map_or(false, |entry_point| entry_point.0 == drop_idx) {
+            if entry_points.last().is_some_and(|entry_point| entry_point.0 == drop_idx) {
                 let block = *blocks[drop_idx].get_or_insert_with(|| T::make_block(cfg));
                 needs_block[drop_idx] = Block::Own;
-                while entry_points.last().map_or(false, |entry_point| entry_point.0 == drop_idx) {
+                while entry_points.last().is_some_and(|entry_point| entry_point.0 == drop_idx) {
                     let entry_block = entry_points.pop().unwrap().1;
                     T::add_entry(cfg, entry_block, block);
                 }
@@ -371,6 +371,7 @@ impl DropTree {
                         // The caller will handle this if needed.
                         unwind: UnwindAction::Terminate,
                         place: drop_data.0.local.into(),
+                        replace: false,
                     };
                     cfg.terminate(block, drop_data.0.source_info, terminator);
                 }
@@ -644,24 +645,27 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             }
         };
 
-        if let Some(destination) = destination {
-            if let Some(value) = value {
+        match (destination, value) {
+            (Some(destination), Some(value)) => {
                 debug!("stmt_expr Break val block_context.push(SubExpr)");
                 self.block_context.push(BlockFrame::SubExpr);
                 unpack!(block = self.expr_into_dest(destination, block, value));
                 self.block_context.pop();
-            } else {
+            }
+            (Some(destination), None) => {
                 self.cfg.push_assign_unit(block, source_info, destination, self.tcx)
             }
-        } else {
-            assert!(value.is_none(), "`return` and `break` should have a destination");
-            if self.tcx.sess.instrument_coverage() {
+            (None, Some(_)) => {
+                panic!("`return`, `become` and `break` with value and must have a destination")
+            }
+            (None, None) if self.tcx.sess.instrument_coverage() => {
                 // Unlike `break` and `return`, which push an `Assign` statement to MIR, from which
                 // a Coverage code region can be generated, `continue` needs no `Assign`; but
                 // without one, the `InstrumentCoverage` MIR pass cannot generate a code region for
                 // `continue`. Coverage will be missing unless we add a dummy `Assign` to MIR.
                 self.add_dummy_assignment(span, block, source_info);
             }
+            (None, None) => {}
         }
 
         let region_scope = self.scopes.breakable_scopes[break_index].region_scope;
@@ -671,12 +675,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         } else {
             self.scopes.breakable_scopes[break_index].continue_drops.as_mut().unwrap()
         };
-        let mut drop_idx = ROOT_NODE;
-        for scope in &self.scopes.scopes[scope_index + 1..] {
-            for drop in &scope.drops {
-                drop_idx = drops.add_drop(*drop, drop_idx);
-            }
-        }
+
+        let drop_idx = self.scopes.scopes[scope_index + 1..]
+            .iter()
+            .flat_map(|scope| &scope.drops)
+            .fold(ROOT_NODE, |drop_idx, &drop| drops.add_drop(drop, drop_idx));
+
         drops.add_entry(block, drop_idx);
 
         // `build_drop_trees` doesn't have access to our source_info, so we
@@ -728,7 +732,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     fn leave_top_scope(&mut self, block: BasicBlock) -> BasicBlock {
         // If we are emitting a `drop` statement, we need to have the cached
         // diverge cleanup pads ready in case that drop panics.
-        let needs_cleanup = self.scopes.scopes.last().map_or(false, |scope| scope.needs_cleanup());
+        let needs_cleanup = self.scopes.scopes.last().is_some_and(|scope| scope.needs_cleanup());
         let is_generator = self.generator_kind.is_some();
         let unwind_to = if needs_cleanup { self.diverge_cleanup() } else { DropIdx::MAX };
 
@@ -1125,9 +1129,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         place: Place<'tcx>,
         value: Rvalue<'tcx>,
     ) -> BlockAnd<()> {
-        let span = self.tcx.with_stable_hashing_context(|hcx| {
-            span.mark_with_reason(None, DesugaringKind::Replace, self.tcx.sess.edition(), hcx)
-        });
         let source_info = self.source_info(span);
 
         // create the new block for the assignment
@@ -1145,6 +1146,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 place,
                 target: assign,
                 unwind: UnwindAction::Cleanup(assign_unwind),
+                replace: true,
             },
         );
         self.diverge_from(block);
@@ -1172,7 +1174,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             TerminatorKind::Assert {
                 cond,
                 expected,
-                msg,
+                msg: Box::new(msg),
                 target: success_block,
                 unwind: UnwindAction::Continue,
             },
@@ -1258,6 +1260,7 @@ fn build_scope_drops<'tcx>(
                         place: local.into(),
                         target: next,
                         unwind: UnwindAction::Continue,
+                        replace: false,
                     },
                 );
                 block = next;
diff --git a/compiler/rustc_mir_build/src/check_unsafety.rs b/compiler/rustc_mir_build/src/check_unsafety.rs
index 03a7f2d70..0506f2bf2 100644
--- a/compiler/rustc_mir_build/src/check_unsafety.rs
+++ b/compiler/rustc_mir_build/src/check_unsafety.rs
@@ -117,10 +117,10 @@ impl<'tcx> UnsafetyVisitor<'_, 'tcx> {
     }
 
     /// Handle closures/generators/inline-consts, which is unsafecked with their parent body.
-    fn visit_inner_body(&mut self, def: ty::WithOptConstParam<LocalDefId>) {
+    fn visit_inner_body(&mut self, def: LocalDefId) {
         if let Ok((inner_thir, expr)) = self.tcx.thir_body(def) {
             let inner_thir = &inner_thir.borrow();
-            let hir_context = self.tcx.hir().local_def_id_to_hir_id(def.did);
+            let hir_context = self.tcx.hir().local_def_id_to_hir_id(def);
             let mut inner_visitor = UnsafetyVisitor { thir: inner_thir, hir_context, ..*self };
             inner_visitor.visit_expr(&inner_thir[expr]);
             // Unsafe blocks can be used in the inner body, make sure to take it into account
@@ -323,6 +323,7 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
             | ExprKind::Box { .. }
             | ExprKind::If { .. }
             | ExprKind::InlineAsm { .. }
+            | ExprKind::OffsetOf { .. }
             | ExprKind::LogicalOp { .. }
             | ExprKind::Use { .. } => {
                 // We don't need to save the old value and restore it
@@ -396,18 +397,11 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
                 movability: _,
                 fake_reads: _,
             }) => {
-                let closure_def = if let Some((did, const_param_id)) =
-                    ty::WithOptConstParam::try_lookup(closure_id, self.tcx)
-                {
-                    ty::WithOptConstParam { did, const_param_did: Some(const_param_id) }
-                } else {
-                    ty::WithOptConstParam::unknown(closure_id)
-                };
-                self.visit_inner_body(closure_def);
+                self.visit_inner_body(closure_id);
             }
             ExprKind::ConstBlock { did, substs: _ } => {
                 let def_id = did.expect_local();
-                self.visit_inner_body(ty::WithOptConstParam::unknown(def_id));
+                self.visit_inner_body(def_id);
             }
             ExprKind::Field { lhs, .. } => {
                 let lhs = &self.thir[lhs];
@@ -706,14 +700,14 @@ impl UnsafeOpKind {
     }
 }
 
-pub fn check_unsafety(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) {
+pub fn thir_check_unsafety(tcx: TyCtxt<'_>, def: LocalDefId) {
     // THIR unsafeck is gated under `-Z thir-unsafeck`
     if !tcx.sess.opts.unstable_opts.thir_unsafeck {
         return;
     }
 
     // Closures and inline consts are handled by their owner, if it has a body
-    if tcx.is_typeck_child(def.did.to_def_id()) {
+    if tcx.is_typeck_child(def.to_def_id()) {
         return;
     }
 
@@ -726,7 +720,7 @@ pub fn check_unsafety(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) {
         return;
     }
 
-    let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
+    let hir_id = tcx.hir().local_def_id_to_hir_id(def);
     let body_unsafety = tcx.hir().fn_sig_by_hir_id(hir_id).map_or(BodyUnsafety::Safe, |fn_sig| {
         if fn_sig.header.unsafety == hir::Unsafety::Unsafe {
             BodyUnsafety::Unsafe(fn_sig.span)
@@ -734,7 +728,7 @@ pub fn check_unsafety(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) {
             BodyUnsafety::Safe
         }
     });
-    let body_target_features = &tcx.body_codegen_attrs(def.did.to_def_id()).target_features;
+    let body_target_features = &tcx.body_codegen_attrs(def.to_def_id()).target_features;
     let safety_context =
         if body_unsafety.is_unsafe() { SafetyContext::UnsafeFn } else { SafetyContext::Safe };
     let mut visitor = UnsafetyVisitor {
@@ -746,23 +740,8 @@ pub fn check_unsafety(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) {
         body_target_features,
         assignment_info: None,
         in_union_destructure: false,
-        param_env: tcx.param_env(def.did),
+        param_env: tcx.param_env(def),
         inside_adt: false,
     };
     visitor.visit_expr(&thir[expr]);
 }
-
-pub(crate) fn thir_check_unsafety(tcx: TyCtxt<'_>, def_id: LocalDefId) {
-    if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
-        tcx.thir_check_unsafety_for_const_arg(def)
-    } else {
-        check_unsafety(tcx, ty::WithOptConstParam::unknown(def_id))
-    }
-}
-
-pub(crate) fn thir_check_unsafety_for_const_arg(
-    tcx: TyCtxt<'_>,
-    (did, param_did): (LocalDefId, DefId),
-) {
-    check_unsafety(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
-}
diff --git a/compiler/rustc_mir_build/src/errors.rs b/compiler/rustc_mir_build/src/errors.rs
index 43e787db4..7c0df201b 100644
--- a/compiler/rustc_mir_build/src/errors.rs
+++ b/compiler/rustc_mir_build/src/errors.rs
@@ -384,13 +384,8 @@ impl<'a> IntoDiagnostic<'a> for NonExhaustivePatternsTypeNotEmpty<'_, '_, '_> {
             diag.span_note(span, fluent::mir_build_def_note);
         }
 
-        let is_variant_list_non_exhaustive = match self.ty.kind() {
-            ty::Adt(def, _) if def.is_variant_list_non_exhaustive() && !def.did().is_local() => {
-                true
-            }
-            _ => false,
-        };
-
+        let is_variant_list_non_exhaustive = matches!(self.ty.kind(),
+            ty::Adt(def, _) if def.is_variant_list_non_exhaustive() && !def.did().is_local());
         if is_variant_list_non_exhaustive {
             diag.note(fluent::mir_build_non_exhaustive_type_note);
         } else {
@@ -786,6 +781,8 @@ pub(crate) struct PatternNotCovered<'s, 'tcx> {
     pub interpreted_as_const: Option<InterpretedAsConst>,
     #[subdiagnostic]
     pub adt_defined_here: Option<AdtDefinedHere<'tcx>>,
+    #[note(mir_build_privately_uninhabited)]
+    pub witness_1_is_privately_uninhabited: Option<()>,
     #[note(mir_build_pattern_ty)]
     pub _p: (),
     pub pattern_ty: Ty<'tcx>,
diff --git a/compiler/rustc_mir_build/src/lib.rs b/compiler/rustc_mir_build/src/lib.rs
index 3f9236c9d..c964e62c9 100644
--- a/compiler/rustc_mir_build/src/lib.rs
+++ b/compiler/rustc_mir_build/src/lib.rs
@@ -22,10 +22,10 @@ mod errors;
 mod lints;
 pub mod thir;
 
-use rustc_middle::ty::query::Providers;
+use rustc_middle::query::Providers;
 
 use rustc_errors::{DiagnosticMessage, SubdiagnosticMessage};
-use rustc_macros::fluent_messages;
+use rustc_fluent_macro::fluent_messages;
 
 fluent_messages! { "../messages.ftl" }
 
@@ -35,7 +35,6 @@ pub fn provide(providers: &mut Providers) {
     providers.lit_to_mir_constant = build::lit_to_mir_constant;
     providers.mir_built = build::mir_built;
     providers.thir_check_unsafety = check_unsafety::thir_check_unsafety;
-    providers.thir_check_unsafety_for_const_arg = check_unsafety::thir_check_unsafety_for_const_arg;
     providers.thir_body = thir::cx::thir_body;
     providers.thir_tree = thir::print::thir_tree;
     providers.thir_flat = thir::print::thir_flat;
diff --git a/compiler/rustc_mir_build/src/thir/cx/block.rs b/compiler/rustc_mir_build/src/thir/cx/block.rs
index 8aacec53f..a46ad6423 100644
--- a/compiler/rustc_mir_build/src/thir/cx/block.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/block.rs
@@ -5,7 +5,7 @@ use rustc_middle::middle::region;
 use rustc_middle::thir::*;
 use rustc_middle::ty;
 
-use rustc_index::vec::Idx;
+use rustc_index::Idx;
 use rustc_middle::ty::CanonicalUserTypeAnnotation;
 
 impl<'tcx> Cx<'tcx> {
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index 8e2e92e6f..b20495d60 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -5,7 +5,7 @@ use crate::thir::util::UserAnnotatedTyHelpers;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
-use rustc_index::vec::Idx;
+use rustc_index::Idx;
 use rustc_middle::hir::place::Place as HirPlace;
 use rustc_middle::hir::place::PlaceBase as HirPlaceBase;
 use rustc_middle::hir::place::ProjectionKind as HirProjectionKind;
@@ -130,6 +130,7 @@ impl<'tcx> Cx<'tcx> {
                 ExprKind::Pointer { cast: PointerCast::Unsize, source: self.thir.exprs.push(expr) }
             }
             Adjust::Pointer(cast) => ExprKind::Pointer { cast, source: self.thir.exprs.push(expr) },
+            Adjust::NeverToAny if adjustment.target.is_never() => return expr,
             Adjust::NeverToAny => ExprKind::NeverToAny { source: self.thir.exprs.push(expr) },
             Adjust::Deref(None) => {
                 adjust_span(&mut expr);
@@ -332,7 +333,7 @@ impl<'tcx> Cx<'tcx> {
                         } else if let Some(box_item) = tcx.lang_items().owned_box() {
                             if let hir::ExprKind::Path(hir::QPath::TypeRelative(ty, fn_path)) = fun.kind
                                 && let hir::TyKind::Path(hir::QPath::Resolved(_, path)) = ty.kind
-                                && path.res.opt_def_id().map_or(false, |did| did == box_item)
+                                && path.res.opt_def_id().is_some_and(|did| did == box_item)
                                 && fn_path.ident.name == sym::new
                                 && let [value] = args
                             {
@@ -664,6 +665,14 @@ impl<'tcx> Cx<'tcx> {
                 line_spans: asm.line_spans,
             })),
 
+            hir::ExprKind::OffsetOf(_, _) => {
+                let data = self.typeck_results.offset_of_data();
+                let &(container, ref indices) = data.get(expr.hir_id).unwrap();
+                let fields = tcx.mk_fields_from_iter(indices.iter().copied());
+
+                ExprKind::OffsetOf { container, fields }
+            }
+
             hir::ExprKind::ConstBlock(ref anon_const) => {
                 let ty = self.typeck_results().node_type(anon_const.hir_id);
                 let did = anon_const.def_id.to_def_id();
@@ -947,7 +956,7 @@ impl<'tcx> Cx<'tcx> {
         let is_upvar = self
             .tcx
             .upvars_mentioned(self.body_owner)
-            .map_or(false, |upvars| upvars.contains_key(&var_hir_id));
+            .is_some_and(|upvars| upvars.contains_key(&var_hir_id));
 
         debug!(
             "convert_var({:?}): is_upvar={}, body_owner={:?}",
diff --git a/compiler/rustc_mir_build/src/thir/cx/mod.rs b/compiler/rustc_mir_build/src/thir/cx/mod.rs
index 070544446..463f639de 100644
--- a/compiler/rustc_mir_build/src/thir/cx/mod.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/mod.rs
@@ -20,25 +20,25 @@ use rustc_span::Span;
 
 pub(crate) fn thir_body(
     tcx: TyCtxt<'_>,
-    owner_def: ty::WithOptConstParam<LocalDefId>,
+    owner_def: LocalDefId,
 ) -> Result<(&Steal<Thir<'_>>, ExprId), ErrorGuaranteed> {
     let hir = tcx.hir();
-    let body = hir.body(hir.body_owned_by(owner_def.did));
+    let body = hir.body(hir.body_owned_by(owner_def));
     let mut cx = Cx::new(tcx, owner_def);
     if let Some(reported) = cx.typeck_results.tainted_by_errors {
         return Err(reported);
     }
     let expr = cx.mirror_expr(&body.value);
 
-    let owner_id = hir.local_def_id_to_hir_id(owner_def.did);
+    let owner_id = hir.local_def_id_to_hir_id(owner_def);
     if let Some(ref fn_decl) = hir.fn_decl_by_hir_id(owner_id) {
-        let closure_env_param = cx.closure_env_param(owner_def.did, owner_id);
+        let closure_env_param = cx.closure_env_param(owner_def, owner_id);
         let explicit_params = cx.explicit_params(owner_id, fn_decl, body);
         cx.thir.params = closure_env_param.into_iter().chain(explicit_params).collect();
 
         // The resume argument may be missing, in that case we need to provide it here.
         // It will always be `()` in this case.
-        if tcx.def_kind(owner_def.did) == DefKind::Generator && body.params.is_empty() {
+        if tcx.def_kind(owner_def) == DefKind::Generator && body.params.is_empty() {
             cx.thir.params.push(Param {
                 ty: tcx.mk_unit(),
                 pat: None,
@@ -78,13 +78,12 @@ struct Cx<'tcx> {
 }
 
 impl<'tcx> Cx<'tcx> {
-    fn new(tcx: TyCtxt<'tcx>, def: ty::WithOptConstParam<LocalDefId>) -> Cx<'tcx> {
-        let typeck_results = tcx.typeck_opt_const_arg(def);
-        let did = def.did;
+    fn new(tcx: TyCtxt<'tcx>, def: LocalDefId) -> Cx<'tcx> {
+        let typeck_results = tcx.typeck(def);
         let hir = tcx.hir();
-        let hir_id = hir.local_def_id_to_hir_id(did);
+        let hir_id = hir.local_def_id_to_hir_id(def);
 
-        let body_type = if hir.body_owner_kind(did).is_fn_or_closure() {
+        let body_type = if hir.body_owner_kind(def).is_fn_or_closure() {
             // fetch the fully liberated fn signature (that is, all bound
             // types/lifetimes replaced)
             BodyTy::Fn(typeck_results.liberated_fn_sigs()[hir_id])
@@ -106,11 +105,11 @@ impl<'tcx> Cx<'tcx> {
         Cx {
             tcx,
             thir: Thir::new(body_type),
-            param_env: tcx.param_env(def.did),
-            region_scope_tree: tcx.region_scope_tree(def.did),
+            param_env: tcx.param_env(def),
+            region_scope_tree: tcx.region_scope_tree(def),
             typeck_results,
             rvalue_scopes: &typeck_results.rvalue_scopes,
-            body_owner: did.to_def_id(),
+            body_owner: def.to_def_id(),
             adjustment_span: None,
             apply_adjustments: hir
                 .attrs(hir_id)
diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
index 8f58db504..1e51cb9aa 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
@@ -26,8 +26,8 @@ use rustc_session::Session;
 use rustc_span::hygiene::DesugaringKind;
 use rustc_span::Span;
 
-pub(crate) fn check_match(tcx: TyCtxt<'_>, def_id: LocalDefId) {
-    let Ok((thir, expr)) = tcx.thir_body(ty::WithOptConstParam::unknown(def_id)) else { return };
+pub(crate) fn check_match(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), ErrorGuaranteed> {
+    let (thir, expr) = tcx.thir_body(def_id)?;
     let thir = thir.borrow();
     let pattern_arena = TypedArena::default();
     let mut visitor = MatchVisitor {
@@ -37,13 +37,16 @@ pub(crate) fn check_match(tcx: TyCtxt<'_>, def_id: LocalDefId) {
         lint_level: tcx.hir().local_def_id_to_hir_id(def_id),
         let_source: LetSource::None,
         pattern_arena: &pattern_arena,
+        error: Ok(()),
     };
     visitor.visit_expr(&thir[expr]);
+
     for param in thir.params.iter() {
         if let Some(box ref pattern) = param.pat {
             visitor.check_irrefutable(pattern, "function argument", None);
         }
     }
+    visitor.error
 }
 
 fn create_e0004(
@@ -77,6 +80,7 @@ struct MatchVisitor<'a, 'p, 'tcx> {
     lint_level: HirId,
     let_source: LetSource,
     pattern_arena: &'p TypedArena<DeconstructedPat<'p, 'tcx>>,
+    error: Result<(), ErrorGuaranteed>,
 }
 
 impl<'a, 'tcx> Visitor<'a, 'tcx> for MatchVisitor<'a, '_, 'tcx> {
@@ -86,35 +90,34 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for MatchVisitor<'a, '_, 'tcx> {
 
     #[instrument(level = "trace", skip(self))]
     fn visit_arm(&mut self, arm: &Arm<'tcx>) {
-        match arm.guard {
-            Some(Guard::If(expr)) => {
-                self.with_let_source(LetSource::IfLetGuard, |this| {
-                    this.visit_expr(&this.thir[expr])
-                });
-            }
-            Some(Guard::IfLet(ref pat, expr)) => {
-                self.with_let_source(LetSource::IfLetGuard, |this| {
-                    this.check_let(pat, expr, LetSource::IfLetGuard, pat.span);
-                    this.visit_pat(pat);
-                    this.visit_expr(&this.thir[expr]);
-                });
+        self.with_lint_level(arm.lint_level, |this| {
+            match arm.guard {
+                Some(Guard::If(expr)) => {
+                    this.with_let_source(LetSource::IfLetGuard, |this| {
+                        this.visit_expr(&this.thir[expr])
+                    });
+                }
+                Some(Guard::IfLet(ref pat, expr)) => {
+                    this.with_let_source(LetSource::IfLetGuard, |this| {
+                        this.check_let(pat, expr, LetSource::IfLetGuard, pat.span);
+                        this.visit_pat(pat);
+                        this.visit_expr(&this.thir[expr]);
+                    });
+                }
+                None => {}
             }
-            None => {}
-        }
-        self.visit_pat(&arm.pattern);
-        self.visit_expr(&self.thir[arm.body]);
+            this.visit_pat(&arm.pattern);
+            this.visit_expr(&self.thir[arm.body]);
+        });
     }
 
     #[instrument(level = "trace", skip(self))]
     fn visit_expr(&mut self, ex: &Expr<'tcx>) {
         match ex.kind {
             ExprKind::Scope { value, lint_level, .. } => {
-                let old_lint_level = self.lint_level;
-                if let LintLevel::Explicit(hir_id) = lint_level {
-                    self.lint_level = hir_id;
-                }
-                self.visit_expr(&self.thir[value]);
-                self.lint_level = old_lint_level;
+                self.with_lint_level(lint_level, |this| {
+                    this.visit_expr(&this.thir[value]);
+                });
                 return;
             }
             ExprKind::If { cond, then, else_opt, if_then_scope: _ } => {
@@ -186,6 +189,17 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
         self.let_source = old_let_source;
     }
 
+    fn with_lint_level(&mut self, new_lint_level: LintLevel, f: impl FnOnce(&mut Self)) {
+        if let LintLevel::Explicit(hir_id) = new_lint_level {
+            let old_lint_level = self.lint_level;
+            self.lint_level = hir_id;
+            f(self);
+            self.lint_level = old_lint_level;
+        } else {
+            f(self);
+        }
+    }
+
     fn check_patterns(&self, pat: &Pat<'tcx>, rf: RefutableFlag) {
         pat.walk_always(|pat| check_borrow_conflicts_in_at_patterns(self, pat));
         check_for_bindings_named_same_as_variants(self, pat, rf);
@@ -232,7 +246,9 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
         for &arm in arms {
             // Check the arm for some things unrelated to exhaustiveness.
             let arm = &self.thir.arms[arm];
-            self.check_patterns(&arm.pattern, Refutable);
+            self.with_lint_level(arm.lint_level, |this| {
+                this.check_patterns(&arm.pattern, Refutable);
+            });
         }
 
         let tarms: Vec<_> = arms
@@ -276,9 +292,9 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
                 let [pat_field] = &subpatterns[..] else { bug!() };
                 self.check_irrefutable(&pat_field.pattern, "`for` loop binding", None);
             } else {
-                non_exhaustive_match(
+                self.error = Err(non_exhaustive_match(
                     &cx, self.thir, scrut_ty, scrut.span, witnesses, arms, expr_span,
-                );
+                ));
             }
         }
     }
@@ -406,7 +422,7 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
     }
 
     #[instrument(level = "trace", skip(self))]
-    fn check_irrefutable(&self, pat: &Pat<'tcx>, origin: &str, sp: Option<Span>) {
+    fn check_irrefutable(&mut self, pat: &Pat<'tcx>, origin: &str, sp: Option<Span>) {
         let mut cx = self.new_cx(self.lint_level, false);
 
         let pattern = self.lower_pattern(&mut cx, pat);
@@ -475,18 +491,36 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
             AdtDefinedHere { adt_def_span, ty, variants }
         };
 
-        self.tcx.sess.emit_err(PatternNotCovered {
+        // Emit an extra note if the first uncovered witness would be uninhabited
+        // if we disregard visibility.
+        let witness_1_is_privately_uninhabited =
+            if cx.tcx.features().exhaustive_patterns
+                && let Some(witness_1) = witnesses.get(0)
+                && let ty::Adt(adt, substs) = witness_1.ty().kind()
+                && adt.is_enum()
+                && let Constructor::Variant(variant_index) = witness_1.ctor()
+            {
+                let variant = adt.variant(*variant_index);
+                let inhabited = variant.inhabited_predicate(cx.tcx, *adt).subst(cx.tcx, substs);
+                assert!(inhabited.apply(cx.tcx, cx.param_env, cx.module));
+                !inhabited.apply_ignore_module(cx.tcx, cx.param_env)
+            } else {
+                false
+            };
+
+        self.error = Err(self.tcx.sess.emit_err(PatternNotCovered {
             span: pat.span,
             origin,
             uncovered: Uncovered::new(pat.span, &cx, witnesses),
             inform,
             interpreted_as_const,
+            witness_1_is_privately_uninhabited: witness_1_is_privately_uninhabited.then_some(()),
             _p: (),
             pattern_ty,
             let_suggestion,
             misc_suggestion,
             adt_defined_here,
-        });
+        }));
     }
 }
 
@@ -628,7 +662,7 @@ fn non_exhaustive_match<'p, 'tcx>(
     witnesses: Vec<DeconstructedPat<'p, 'tcx>>,
     arms: &[ArmId],
     expr_span: Span,
-) {
+) -> ErrorGuaranteed {
     let is_empty_match = arms.is_empty();
     let non_empty_enum = match scrut_ty.kind() {
         ty::Adt(def, _) => def.is_enum() && !def.variants().is_empty(),
@@ -640,13 +674,12 @@ fn non_exhaustive_match<'p, 'tcx>(
     let pattern;
     let patterns_len;
     if is_empty_match && !non_empty_enum {
-        cx.tcx.sess.emit_err(NonExhaustivePatternsTypeNotEmpty {
+        return cx.tcx.sess.emit_err(NonExhaustivePatternsTypeNotEmpty {
             cx,
             expr_span,
             span: sp,
             ty: scrut_ty,
         });
-        return;
     } else {
         // FIXME: migration of this diagnostic will require list support
         let joined_patterns = joined_uncovered_patterns(cx, &witnesses);
@@ -668,13 +701,11 @@ fn non_exhaustive_match<'p, 'tcx>(
         };
     };
 
-    let is_variant_list_non_exhaustive = match scrut_ty.kind() {
-        ty::Adt(def, _) if def.is_variant_list_non_exhaustive() && !def.did().is_local() => true,
-        _ => false,
-    };
+    let is_variant_list_non_exhaustive = matches!(scrut_ty.kind(),
+        ty::Adt(def, _) if def.is_variant_list_non_exhaustive() && !def.did().is_local());
 
     adt_defined_here(cx, &mut err, scrut_ty, &witnesses);
-    err.note(&format!(
+    err.note(format!(
         "the matched value is of type `{}`{}",
         scrut_ty,
         if is_variant_list_non_exhaustive { ", which is marked as non-exhaustive" } else { "" }
@@ -684,13 +715,13 @@ fn non_exhaustive_match<'p, 'tcx>(
         && witnesses.len() == 1
         && matches!(witnesses[0].ctor(), Constructor::NonExhaustive)
     {
-        err.note(&format!(
+        err.note(format!(
             "`{}` does not have a fixed maximum value, so a wildcard `_` is necessary to match \
              exhaustively",
             scrut_ty,
         ));
         if cx.tcx.sess.is_nightly_build() {
-            err.help(&format!(
+            err.help(format!(
                 "add `#![feature(precise_pointer_size_matching)]` to the crate attributes to \
                  enable precise `{}` matching",
                 scrut_ty,
@@ -795,11 +826,11 @@ fn non_exhaustive_match<'p, 'tcx>(
         },
     );
     if let Some((span, sugg)) = suggestion {
-        err.span_suggestion_verbose(span, &msg, sugg, Applicability::HasPlaceholders);
+        err.span_suggestion_verbose(span, msg, sugg, Applicability::HasPlaceholders);
     } else {
-        err.help(&msg);
+        err.help(msg);
     }
-    err.emit();
+    err.emit()
 }
 
 pub(crate) fn joined_uncovered_patterns<'p, 'tcx>(
@@ -859,7 +890,7 @@ fn adt_defined_here<'p, 'tcx>(
         for pat in spans {
             span.push_span_label(pat, "not covered");
         }
-        err.span_note(span, &format!("`{}` defined here", ty));
+        err.span_note(span, format!("`{}` defined here", ty));
     }
 }
 
diff --git a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
index 32d0404bd..b243f1dc8 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
@@ -1,5 +1,5 @@
 use rustc_hir as hir;
-use rustc_index::vec::Idx;
+use rustc_index::Idx;
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::Obligation;
 use rustc_middle::mir;
@@ -62,21 +62,13 @@ struct ConstToPat<'tcx> {
     treat_byte_string_as_slice: bool,
 }
 
-mod fallback_to_const_ref {
-    #[derive(Debug)]
-    /// This error type signals that we encountered a non-struct-eq situation behind a reference.
-    /// We bubble this up in order to get back to the reference destructuring and make that emit
-    /// a const pattern instead of a deref pattern. This allows us to simply call `PartialEq::eq`
-    /// on such patterns (since that function takes a reference) and not have to jump through any
-    /// hoops to get a reference to the value.
-    pub(super) struct FallbackToConstRef(());
-
-    pub(super) fn fallback_to_const_ref(c2p: &super::ConstToPat<'_>) -> FallbackToConstRef {
-        assert!(c2p.behind_reference.get());
-        FallbackToConstRef(())
-    }
-}
-use fallback_to_const_ref::{fallback_to_const_ref, FallbackToConstRef};
+/// This error type signals that we encountered a non-struct-eq situation.
+/// We bubble this up in order to get back to the reference destructuring and make that emit
+/// a const pattern instead of a deref pattern. This allows us to simply call `PartialEq::eq`
+/// on such patterns (since that function takes a reference) and not have to jump through any
+/// hoops to get a reference to the value.
+#[derive(Debug)]
+struct FallbackToConstRef;
 
 impl<'tcx> ConstToPat<'tcx> {
     fn new(
@@ -156,7 +148,7 @@ impl<'tcx> ConstToPat<'tcx> {
 
             if let Some(non_sm_ty) = structural {
                 if !self.type_may_have_partial_eq_impl(cv.ty()) {
-                    // fatal avoids ICE from resolution of non-existent method (rare case).
+                    // fatal avoids ICE from resolution of nonexistent method (rare case).
                     self.tcx()
                         .sess
                         .emit_fatal(TypeNotStructural { span: self.span, non_sm_ty: non_sm_ty });
@@ -191,7 +183,7 @@ impl<'tcx> ConstToPat<'tcx> {
             self.tcx(),
             ObligationCause::dummy(),
             self.param_env,
-            self.tcx().mk_trait_ref(partial_eq_trait_id, [ty, ty]),
+            ty::TraitRef::new(self.tcx(), partial_eq_trait_id, [ty, ty]),
         );
 
         // FIXME: should this call a `predicate_must_hold` variant instead?
@@ -236,13 +228,13 @@ impl<'tcx> ConstToPat<'tcx> {
 
         let kind = match cv.ty().kind() {
             ty::Float(_) => {
-                    tcx.emit_spanned_lint(
-                        lint::builtin::ILLEGAL_FLOATING_POINT_LITERAL_PATTERN,
-                        id,
-                        span,
-                        FloatPattern,
-                    );
-                PatKind::Constant { value: cv }
+                tcx.emit_spanned_lint(
+                    lint::builtin::ILLEGAL_FLOATING_POINT_LITERAL_PATTERN,
+                    id,
+                    span,
+                    FloatPattern,
+                );
+                return Err(FallbackToConstRef);
             }
             ty::Adt(adt_def, _) if adt_def.is_union() => {
                 // Matching on union fields is unsafe, we can't hide it in constants
@@ -289,7 +281,7 @@ impl<'tcx> ConstToPat<'tcx> {
                 // Since we are behind a reference, we can just bubble the error up so we get a
                 // constant at reference type, making it easy to let the fallback call
                 // `PartialEq::eq` on it.
-                return Err(fallback_to_const_ref(self));
+                return Err(FallbackToConstRef);
             }
             ty::Adt(adt_def, _) if !self.type_marked_structural(cv.ty()) => {
                 debug!(
@@ -393,11 +385,11 @@ impl<'tcx> ConstToPat<'tcx> {
                     self.behind_reference.set(old);
                     val
                 }
-                // Backwards compatibility hack: support references to non-structural types.
-                // We'll lower
-                // this pattern to a `PartialEq::eq` comparison and `PartialEq::eq` takes a
-                // reference. This makes the rest of the matching logic simpler as it doesn't have
-                // to figure out how to get a reference again.
+                // Backwards compatibility hack: support references to non-structural types,
+                // but hard error if we aren't behind a double reference. We could just use
+                // the fallback code path below, but that would allow *more* of this fishy
+                // code to compile, as then it only goes through the future incompat lint
+                // instead of a hard error.
                 ty::Adt(_, _) if !self.type_marked_structural(*pointee_ty) => {
                     if self.behind_reference.get() {
                         if !self.saw_const_match_error.get()
@@ -411,7 +403,7 @@ impl<'tcx> ConstToPat<'tcx> {
                                 IndirectStructuralMatch { non_sm_ty: *pointee_ty },
                             );
                         }
-                        PatKind::Constant { value: cv }
+                        return Err(FallbackToConstRef);
                     } else {
                         if !self.saw_const_match_error.get() {
                             self.saw_const_match_error.set(true);
@@ -435,16 +427,9 @@ impl<'tcx> ConstToPat<'tcx> {
                         PatKind::Wild
                     } else {
                         let old = self.behind_reference.replace(true);
-                        // In case there are structural-match violations somewhere in this subpattern,
-                        // we fall back to a const pattern. If we do not do this, we may end up with
-                        // a !structural-match constant that is not of reference type, which makes it
-                        // very hard to invoke `PartialEq::eq` on it as a fallback.
-                        let val = match self.recur(tcx.deref_mir_constant(self.param_env.and(cv)), false) {
-                            Ok(subpattern) => PatKind::Deref { subpattern },
-                            Err(_) => PatKind::Constant { value: cv },
-                        };
+                        let subpattern = self.recur(tcx.deref_mir_constant(self.param_env.and(cv)), false)?;
                         self.behind_reference.set(old);
-                        val
+                        PatKind::Deref { subpattern }
                     }
                 }
             },
@@ -452,7 +437,7 @@ impl<'tcx> ConstToPat<'tcx> {
                 PatKind::Constant { value: cv }
             }
             ty::RawPtr(pointee) if pointee.ty.is_sized(tcx, param_env) => {
-                PatKind::Constant { value: cv }
+                return Err(FallbackToConstRef);
             }
             // FIXME: these can have very surprising behaviour where optimization levels or other
             // compilation choices change the runtime behaviour of the match.
@@ -469,7 +454,7 @@ impl<'tcx> ConstToPat<'tcx> {
                         PointerPattern
                     );
                 }
-                PatKind::Constant { value: cv }
+                return Err(FallbackToConstRef);
             }
             _ => {
                 self.saw_const_match_error.set(true);
diff --git a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
index 7c2919644..6a7714613 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
@@ -52,7 +52,7 @@ use smallvec::{smallvec, SmallVec};
 
 use rustc_data_structures::captures::Captures;
 use rustc_hir::{HirId, RangeEnd};
-use rustc_index::vec::Idx;
+use rustc_index::Idx;
 use rustc_middle::mir;
 use rustc_middle::thir::{FieldPat, Pat, PatKind, PatRange};
 use rustc_middle::ty::layout::IntegerExt;
@@ -844,8 +844,8 @@ impl<'tcx> Constructor<'tcx> {
     }
 
     /// Faster version of `is_covered_by` when applied to many constructors. `used_ctors` is
-    /// assumed to be built from `matrix.head_ctors()` with wildcards filtered out, and `self` is
-    /// assumed to have been split from a wildcard.
+    /// assumed to be built from `matrix.head_ctors()` with wildcards and opaques filtered out,
+    /// and `self` is assumed to have been split from a wildcard.
     fn is_covered_by_any<'p>(
         &self,
         pcx: &PatCtxt<'_, 'p, 'tcx>,
@@ -894,7 +894,7 @@ impl<'tcx> Constructor<'tcx> {
 /// in `to_ctors`: in some cases we only return `Missing`.
 #[derive(Debug)]
 pub(super) struct SplitWildcard<'tcx> {
-    /// Constructors seen in the matrix.
+    /// Constructors (other than wildcards and opaques) seen in the matrix.
     matrix_ctors: Vec<Constructor<'tcx>>,
     /// All the constructors for this type
     all_ctors: SmallVec<[Constructor<'tcx>; 1]>,
@@ -1037,7 +1037,7 @@ impl<'tcx> SplitWildcard<'tcx> {
         // Since `all_ctors` never contains wildcards, this won't recurse further.
         self.all_ctors =
             self.all_ctors.iter().flat_map(|ctor| ctor.split(pcx, ctors.clone())).collect();
-        self.matrix_ctors = ctors.filter(|c| !c.is_wildcard()).cloned().collect();
+        self.matrix_ctors = ctors.filter(|c| !matches!(c, Wildcard | Opaque)).cloned().collect();
     }
 
     /// Whether there are any value constructors for this type that are not present in the matrix.
diff --git a/compiler/rustc_mir_build/src/thir/pattern/mod.rs b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
index 70d015a39..1cf2f7ec0 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/mod.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
@@ -16,7 +16,7 @@ use rustc_hir as hir;
 use rustc_hir::def::{CtorOf, DefKind, Res};
 use rustc_hir::pat_util::EnumerateAndAdjustIterator;
 use rustc_hir::RangeEnd;
-use rustc_index::vec::Idx;
+use rustc_index::Idx;
 use rustc_middle::mir::interpret::{
     ConstValue, ErrorHandled, LitToConstError, LitToConstInput, Scalar,
 };
@@ -229,7 +229,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
                         self.lower_pattern_range(ty, lc, hc, end, lo_span, lo_expr, hi_expr)
                     }
                     None => {
-                        let msg = &format!(
+                        let msg = format!(
                             "found bad range pattern `{:?}` outside of error recovery",
                             (&lo, &hi),
                         );
diff --git a/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs b/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
index d8f66a175..e5b635069 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
@@ -288,6 +288,22 @@
 //!
 //! The details are not necessary to understand this file, so we explain them in
 //! [`super::deconstruct_pat`]. Splitting is done by the [`Constructor::split`] function.
+//!
+//! # Constants in patterns
+//!
+//! There are two kinds of constants in patterns:
+//!
+//! * literals (`1`, `true`, `"foo"`)
+//! * named or inline consts (`FOO`, `const { 5 + 6 }`)
+//!
+//! The latter are converted into other patterns with literals at the leaves. For example
+//! `const_to_pat(const { [1, 2, 3] })` becomes an `Array(vec![Const(1), Const(2), Const(3)])`
+//! pattern. This gets problematic when comparing the constant via `==` would behave differently
+//! from matching on the constant converted to a pattern. Situations like that can occur, when
+//! the user implements `PartialEq` manually, and thus could make `==` behave arbitrarily different.
+//! In order to honor the `==` implementation, constants of types that implement `PartialEq` manually
+//! stay as a full constant and become an `Opaque` pattern. These `Opaque` patterns do not participate
+//! in exhaustiveness, specialization or overlap checking.
 
 use self::ArmType::*;
 use self::Usefulness::*;
@@ -685,10 +701,9 @@ enum ArmType {
 /// For example, if we are constructing a witness for the match against
 ///
 /// ```compile_fail,E0004
-/// # #![feature(type_ascription)]
 /// struct Pair(Option<(u32, u32)>, bool);
 /// # fn foo(p: Pair) {
-/// match (p: Pair) {
+/// match p {
 ///    Pair(None, _) => {}
 ///    Pair(_, false) => {}
 /// }
diff --git a/compiler/rustc_mir_build/src/thir/print.rs b/compiler/rustc_mir_build/src/thir/print.rs
index ed61d6ee7..b2f2a64e2 100644
--- a/compiler/rustc_mir_build/src/thir/print.rs
+++ b/compiler/rustc_mir_build/src/thir/print.rs
@@ -3,7 +3,7 @@ use rustc_middle::ty::{self, TyCtxt};
 use rustc_span::def_id::LocalDefId;
 use std::fmt::{self, Write};
 
-pub(crate) fn thir_tree(tcx: TyCtxt<'_>, owner_def: ty::WithOptConstParam<LocalDefId>) -> String {
+pub(crate) fn thir_tree(tcx: TyCtxt<'_>, owner_def: LocalDefId) -> String {
     match super::cx::thir_body(tcx, owner_def) {
         Ok((thir, _)) => {
             let thir = thir.steal();
@@ -15,7 +15,7 @@ pub(crate) fn thir_tree(tcx: TyCtxt<'_>, owner_def: ty::WithOptConstParam<LocalD
     }
 }
 
-pub(crate) fn thir_flat(tcx: TyCtxt<'_>, owner_def: ty::WithOptConstParam<LocalDefId>) -> String {
+pub(crate) fn thir_flat(tcx: TyCtxt<'_>, owner_def: LocalDefId) -> String {
     match super::cx::thir_body(tcx, owner_def) {
         Ok((thir, _)) => format!("{:#?}", thir.steal()),
         Err(_) => "error".into(),
@@ -519,6 +519,19 @@ impl<'a, 'tcx> ThirPrinter<'a, 'tcx> {
                 self.print_inline_asm_expr(&**expr, depth_lvl + 2);
                 print_indented!(self, "}", depth_lvl);
             }
+            OffsetOf { container, fields } => {
+                print_indented!(self, "OffsetOf {", depth_lvl);
+                print_indented!(self, format!("container: {:?}", container), depth_lvl + 1);
+                print_indented!(self, "fields: [", depth_lvl + 1);
+
+                for field in fields.iter() {
+                    print_indented!(self, format!("{:?}", field), depth_lvl + 2);
+                    print_indented!(self, ",", depth_lvl + 1);
+                }
+
+                print_indented!(self, "]", depth_lvl + 1);
+                print_indented!(self, "}", depth_lvl);
+            }
             ThreadLocalRef(def_id) => {
                 print_indented!(self, "ThreadLocalRef {", depth_lvl);
                 print_indented!(self, format!("def_id: {:?}", def_id), depth_lvl + 1);