4 files changed, 101 insertions, 0 deletions
diff --git a/tests/ui/consts/extra-const-ub/detect-extra-ub.rs b/tests/ui/consts/extra-const-ub/detect-extra-ub.rs
new file mode 100644
index 000000000..e2f814988
--- /dev/null
+++ b/tests/ui/consts/extra-const-ub/detect-extra-ub.rs
@@ -0,0 +1,31 @@
+// revisions: no_flag with_flag
+// [no_flag] check-pass
+// [with_flag] compile-flags: -Zextra-const-ub-checks
+#![feature(const_ptr_read)]
+
+use std::mem::transmute;
+
+const INVALID_BOOL: () = unsafe {
+    let _x: bool = transmute(3u8);
+    //[with_flag]~^ ERROR: evaluation of constant value failed
+    //[with_flag]~| invalid value
+};
+
+const INVALID_PTR_IN_INT: () = unsafe {
+    let _x: usize = transmute(&3u8);
+    //[with_flag]~^ ERROR: evaluation of constant value failed
+};
+
+const INVALID_SLICE_TO_USIZE_TRANSMUTE: () = unsafe {
+    let x: &[u8] = &[0; 32];
+    let _x: (usize, usize) = transmute(x);
+    //[with_flag]~^ ERROR: evaluation of constant value failed
+};
+
+const UNALIGNED_PTR: () = unsafe {
+    let _x: &u32 = transmute(&[0u8; 4]);
+    //[with_flag]~^ ERROR: evaluation of constant value failed
+    //[with_flag]~| invalid value
+};
+
+fn main() {}
diff --git a/tests/ui/consts/extra-const-ub/detect-extra-ub.with_flag.stderr b/tests/ui/consts/extra-const-ub/detect-extra-ub.with_flag.stderr
new file mode 100644
index 000000000..b2a5fd901
--- /dev/null
+++ b/tests/ui/consts/extra-const-ub/detect-extra-ub.with_flag.stderr
@@ -0,0 +1,33 @@
+error[E0080]: evaluation of constant value failed
+  --> $DIR/detect-extra-ub.rs:9:20
+   |
+LL |     let _x: bool = transmute(3u8);
+   |                    ^^^^^^^^^^^^^^ constructing invalid value: encountered 0x03, but expected a boolean
+
+error[E0080]: evaluation of constant value failed
+  --> $DIR/detect-extra-ub.rs:15:21
+   |
+LL |     let _x: usize = transmute(&3u8);
+   |                     ^^^^^^^^^^^^^^^ unable to turn pointer into raw bytes
+   |
+   = help: this code performed an operation that depends on the underlying bytes representing a pointer
+   = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported
+
+error[E0080]: evaluation of constant value failed
+  --> $DIR/detect-extra-ub.rs:21:30
+   |
+LL |     let _x: (usize, usize) = transmute(x);
+   |                              ^^^^^^^^^^^^ unable to turn pointer into raw bytes
+   |
+   = help: this code performed an operation that depends on the underlying bytes representing a pointer
+   = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported
+
+error[E0080]: evaluation of constant value failed
+  --> $DIR/detect-extra-ub.rs:26:20
+   |
+LL |     let _x: &u32 = transmute(&[0u8; 4]);
+   |                    ^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered an unaligned reference (required 4 byte alignment but found 1)
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0080`.
diff --git a/tests/ui/consts/extra-const-ub/issue-100771.rs b/tests/ui/consts/extra-const-ub/issue-100771.rs
new file mode 100644
index 000000000..a32960328
--- /dev/null
+++ b/tests/ui/consts/extra-const-ub/issue-100771.rs
@@ -0,0 +1,20 @@
+// check-pass
+// compile-flags: -Zextra-const-ub-checks
+
+#[derive(PartialEq, Eq, Copy, Clone)]
+#[repr(packed)]
+struct Foo {
+    field: (i64, u32, u32, u32),
+}
+
+const FOO: Foo = Foo {
+    field: (5, 6, 7, 8),
+};
+
+fn main() {
+    match FOO {
+        Foo { field: (5, 6, 7, 8) } => {},
+        FOO => unreachable!(),
+        _ => unreachable!(),
+    }
+}
diff --git a/tests/ui/consts/extra-const-ub/issue-101034.rs b/tests/ui/consts/extra-const-ub/issue-101034.rs
new file mode 100644
index 000000000..e0de705c4
--- /dev/null
+++ b/tests/ui/consts/extra-const-ub/issue-101034.rs
@@ -0,0 +1,17 @@
+// check-pass
+// compile-flags: -Zextra-const-ub-checks
+
+#[repr(packed)]
+pub struct Foo {
+    bar: u8,
+    baa: [u32; 1],
+}
+
+const FOOMP: Foo = Foo {
+    bar: 0,
+    baa: [69; 1],
+};
+
+fn main() {
+    let _val = FOOMP;
+}