Merging upstream version 1.74.1+dfsg1.

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

22 files changed, 608 insertions, 259 deletions

diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/const-expr.rs b/tests/ui/rfcs/rfc-2294-if-let-guard/const-expr.rs
new file mode 100644
index 000000000..5c42c0d8b
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/const-expr.rs
@@ -0,0 +1,26 @@
+// Ensure if let guards can be used in constant expressions.
+// build-pass
+
+#![feature(if_let_guard)]
+
+const fn match_if_let(x: Option<i32>, y: Option<i32>) -> i32 {
+    match x {
+        None if let Some(a @ 5) = y => a,
+        Some(z) if let (Some(_), 12) = (y, z) => 2,
+        _ => 3,
+    }
+}
+
+const ASSERTS: usize = {
+    assert!(match_if_let(None, Some(5)) == 5);
+    assert!(match_if_let(Some(12), Some(3)) == 2);
+    assert!(match_if_let(None, Some(4)) == 3);
+    assert!(match_if_let(Some(11), Some(3)) == 3);
+    assert!(match_if_let(Some(12), None) == 3);
+    assert!(match_if_let(None, None) == 3);
+    0
+};
+
+fn main() {
+    let _: [(); ASSERTS];
+}
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/exhaustive.rs b/tests/ui/rfcs/rfc-2294-if-let-guard/exhaustive.rs
new file mode 100644
index 000000000..b4eb54139
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/exhaustive.rs
@@ -0,0 +1,18 @@
+#![feature(if_let_guard)]
+#![allow(irrefutable_let_patterns)]
+
+fn match_option(x: Option<u32>) {
+    match x {
+        //~^ ERROR non-exhaustive patterns: `None` not covered
+        Some(_) => {}
+        None if let y = x => {}
+    }
+}
+
+fn main() {
+    let x = ();
+    match x {
+        //~^ ERROR non-exhaustive patterns: `()` not covered
+        y if let z = y => {}
+    }
+}
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/exhaustive.stderr b/tests/ui/rfcs/rfc-2294-if-let-guard/exhaustive.stderr
new file mode 100644
index 000000000..ddd08854f
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/exhaustive.stderr
@@ -0,0 +1,35 @@
+error[E0004]: non-exhaustive patterns: `None` not covered
+  --> $DIR/exhaustive.rs:5:11
+   |
+LL |     match x {
+   |           ^ pattern `None` not covered
+   |
+note: `Option<u32>` defined here
+  --> $SRC_DIR/core/src/option.rs:LL:COL
+  ::: $SRC_DIR/core/src/option.rs:LL:COL
+   |
+   = note: not covered
+   = note: the matched value is of type `Option<u32>`
+help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
+   |
+LL ~         None if let y = x => {},
+LL +         None => todo!()
+   |
+
+error[E0004]: non-exhaustive patterns: `()` not covered
+  --> $DIR/exhaustive.rs:14:11
+   |
+LL |     match x {
+   |           ^ pattern `()` not covered
+   |
+   = note: the matched value is of type `()`
+   = note: match arms with guards don't count towards exhaustivity
+help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
+   |
+LL ~         y if let z = y => {},
+LL +         () => todo!()
+   |
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0004`.
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/feature-gate.rs b/tests/ui/rfcs/rfc-2294-if-let-guard/feature-gate.rs
index 3beb20f0a..b8c0eb3e6 100644
--- a/tests/ui/rfcs/rfc-2294-if-let-guard/feature-gate.rs
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/feature-gate.rs
@@ -8,14 +8,10 @@ fn _if_let_guard() {
         //~^ ERROR `if let` guards are experimental
 
         () if (let 0 = 1) => {}
-        //~^ ERROR `let` expressions in this position are unstable
-        //~| ERROR expected expression, found `let` statement
-        //~| ERROR `let` expressions are not supported here
+        //~^ ERROR expected expression, found `let` statement
 
         () if (((let 0 = 1))) => {}
-        //~^ ERROR `let` expressions in this position are unstable
-        //~| ERROR expected expression, found `let` statement
-        //~| ERROR `let` expressions are not supported here
+        //~^ ERROR expected expression, found `let` statement
 
         () if true && let 0 = 1 => {}
         //~^ ERROR `if let` guards are experimental
@@ -26,36 +22,22 @@ fn _if_let_guard() {
         //~| ERROR `let` expressions in this position are unstable
 
         () if (let 0 = 1) && true => {}
-        //~^ ERROR `let` expressions in this position are unstable
-        //~| ERROR expected expression, found `let` statement
-        //~| ERROR `let` expressions are not supported here
+        //~^ ERROR expected expression, found `let` statement
 
         () if true && (let 0 = 1) => {}
-        //~^ ERROR `let` expressions in this position are unstable
-        //~| ERROR expected expression, found `let` statement
-        //~| ERROR `let` expressions are not supported here
+        //~^ ERROR expected expression, found `let` statement
 
         () if (let 0 = 1) && (let 0 = 1) => {}
-        //~^ ERROR `let` expressions in this position are unstable
-        //~| ERROR `let` expressions in this position are unstable
+        //~^ ERROR expected expression, found `let` statement
         //~| ERROR expected expression, found `let` statement
-        //~| ERROR expected expression, found `let` statement
-        //~| ERROR `let` expressions are not supported here
-        //~| ERROR `let` expressions are not supported here
 
         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
         //~^ ERROR `if let` guards are experimental
         //~| ERROR `let` expressions in this position are unstable
         //~| ERROR `let` expressions in this position are unstable
-        //~| ERROR `let` expressions in this position are unstable
-        //~| ERROR `let` expressions in this position are unstable
-        //~| ERROR `let` expressions in this position are unstable
         //~| ERROR expected expression, found `let` statement
         //~| ERROR expected expression, found `let` statement
         //~| ERROR expected expression, found `let` statement
-        //~| ERROR `let` expressions are not supported here
-        //~| ERROR `let` expressions are not supported here
-        //~| ERROR `let` expressions are not supported here
 
 
         () if let Range { start: _, end: _ } = (true..true) && false => {}
@@ -76,13 +58,9 @@ fn _macros() {
         }
     }
     use_expr!((let 0 = 1 && 0 == 0));
-    //~^ ERROR `let` expressions in this position are unstable
-    //~| ERROR expected expression, found `let` statement
-    //~| ERROR `let` expressions are not supported here
+    //~^ ERROR expected expression, found `let` statement
     use_expr!((let 0 = 1));
-    //~^ ERROR `let` expressions in this position are unstable
-    //~| ERROR expected expression, found `let` statement
-    //~| ERROR `let` expressions are not supported here
+    //~^ ERROR expected expression, found `let` statement
     match () {
         #[cfg(FALSE)]
         () if let 0 = 1 => {}
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/feature-gate.stderr b/tests/ui/rfcs/rfc-2294-if-let-guard/feature-gate.stderr
index dc182ce46..62534b555 100644
--- a/tests/ui/rfcs/rfc-2294-if-let-guard/feature-gate.stderr
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/feature-gate.stderr
@@ -2,87 +2,6 @@ error: expected expression, found `let` statement
   --> $DIR/feature-gate.rs:10:16
    |
 LL |         () if (let 0 = 1) => {}
-   |                ^^^
-
-error: expected expression, found `let` statement
-  --> $DIR/feature-gate.rs:15:18
-   |
-LL |         () if (((let 0 = 1))) => {}
-   |                  ^^^
-
-error: expected expression, found `let` statement
-  --> $DIR/feature-gate.rs:28:16
-   |
-LL |         () if (let 0 = 1) && true => {}
-   |                ^^^
-
-error: expected expression, found `let` statement
-  --> $DIR/feature-gate.rs:33:24
-   |
-LL |         () if true && (let 0 = 1) => {}
-   |                        ^^^
-
-error: expected expression, found `let` statement
-  --> $DIR/feature-gate.rs:38:16
-   |
-LL |         () if (let 0 = 1) && (let 0 = 1) => {}
-   |                ^^^
-
-error: expected expression, found `let` statement
-  --> $DIR/feature-gate.rs:38:31
-   |
-LL |         () if (let 0 = 1) && (let 0 = 1) => {}
-   |                               ^^^
-
-error: expected expression, found `let` statement
-  --> $DIR/feature-gate.rs:46:42
-   |
-LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
-   |                                          ^^^
-
-error: expected expression, found `let` statement
-  --> $DIR/feature-gate.rs:46:55
-   |
-LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
-   |                                                       ^^^
-
-error: expected expression, found `let` statement
-  --> $DIR/feature-gate.rs:46:68
-   |
-LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
-   |                                                                    ^^^
-
-error: expected expression, found `let` statement
-  --> $DIR/feature-gate.rs:78:16
-   |
-LL |     use_expr!((let 0 = 1 && 0 == 0));
-   |                ^^^
-
-error: expected expression, found `let` statement
-  --> $DIR/feature-gate.rs:82:16
-   |
-LL |     use_expr!((let 0 = 1));
-   |                ^^^
-
-error: no rules expected the token `let`
-  --> $DIR/feature-gate.rs:92:15
-   |
-LL |     macro_rules! use_expr {
-   |     --------------------- when calling this macro
-...
-LL |     use_expr!(let 0 = 1);
-   |               ^^^ no rules expected this token in macro call
-   |
-note: while trying to match meta-variable `$e:expr`
-  --> $DIR/feature-gate.rs:71:10
-   |
-LL |         ($e:expr) => {
-   |          ^^^^^^^
-
-error: `let` expressions are not supported here
-  --> $DIR/feature-gate.rs:10:16
-   |
-LL |         () if (let 0 = 1) => {}
    |                ^^^^^^^^^
    |
    = note: only supported directly in conditions of `if` and `while` expressions
@@ -92,135 +11,140 @@ note: `let`s wrapped in parentheses are not supported in a context with let chai
 LL |         () if (let 0 = 1) => {}
    |                ^^^^^^^^^
 
-error: `let` expressions are not supported here
-  --> $DIR/feature-gate.rs:15:18
+error: expected expression, found `let` statement
+  --> $DIR/feature-gate.rs:13:18
    |
 LL |         () if (((let 0 = 1))) => {}
    |                  ^^^^^^^^^
    |
    = note: only supported directly in conditions of `if` and `while` expressions
 note: `let`s wrapped in parentheses are not supported in a context with let chains
-  --> $DIR/feature-gate.rs:15:18
+  --> $DIR/feature-gate.rs:13:18
    |
 LL |         () if (((let 0 = 1))) => {}
    |                  ^^^^^^^^^
 
-error: `let` expressions are not supported here
-  --> $DIR/feature-gate.rs:28:16
+error: expected expression, found `let` statement
+  --> $DIR/feature-gate.rs:24:16
    |
 LL |         () if (let 0 = 1) && true => {}
    |                ^^^^^^^^^
    |
    = note: only supported directly in conditions of `if` and `while` expressions
 note: `let`s wrapped in parentheses are not supported in a context with let chains
-  --> $DIR/feature-gate.rs:28:16
+  --> $DIR/feature-gate.rs:24:16
    |
 LL |         () if (let 0 = 1) && true => {}
    |                ^^^^^^^^^
 
-error: `let` expressions are not supported here
-  --> $DIR/feature-gate.rs:33:24
+error: expected expression, found `let` statement
+  --> $DIR/feature-gate.rs:27:24
    |
 LL |         () if true && (let 0 = 1) => {}
    |                        ^^^^^^^^^
    |
    = note: only supported directly in conditions of `if` and `while` expressions
 note: `let`s wrapped in parentheses are not supported in a context with let chains
-  --> $DIR/feature-gate.rs:33:24
+  --> $DIR/feature-gate.rs:27:24
    |
 LL |         () if true && (let 0 = 1) => {}
    |                        ^^^^^^^^^
 
-error: `let` expressions are not supported here
-  --> $DIR/feature-gate.rs:38:16
+error: expected expression, found `let` statement
+  --> $DIR/feature-gate.rs:30:16
    |
 LL |         () if (let 0 = 1) && (let 0 = 1) => {}
    |                ^^^^^^^^^
    |
    = note: only supported directly in conditions of `if` and `while` expressions
 note: `let`s wrapped in parentheses are not supported in a context with let chains
-  --> $DIR/feature-gate.rs:38:16
+  --> $DIR/feature-gate.rs:30:16
    |
 LL |         () if (let 0 = 1) && (let 0 = 1) => {}
    |                ^^^^^^^^^
 
-error: `let` expressions are not supported here
-  --> $DIR/feature-gate.rs:38:31
+error: expected expression, found `let` statement
+  --> $DIR/feature-gate.rs:30:31
    |
 LL |         () if (let 0 = 1) && (let 0 = 1) => {}
    |                               ^^^^^^^^^
    |
    = note: only supported directly in conditions of `if` and `while` expressions
 note: `let`s wrapped in parentheses are not supported in a context with let chains
-  --> $DIR/feature-gate.rs:38:31
+  --> $DIR/feature-gate.rs:30:31
    |
 LL |         () if (let 0 = 1) && (let 0 = 1) => {}
    |                               ^^^^^^^^^
 
-error: `let` expressions are not supported here
-  --> $DIR/feature-gate.rs:46:42
+error: expected expression, found `let` statement
+  --> $DIR/feature-gate.rs:34:42
    |
 LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
    |                                          ^^^^^^^^^
    |
    = note: only supported directly in conditions of `if` and `while` expressions
 note: `let`s wrapped in parentheses are not supported in a context with let chains
-  --> $DIR/feature-gate.rs:46:42
+  --> $DIR/feature-gate.rs:34:42
    |
 LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
    |                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: `let` expressions are not supported here
-  --> $DIR/feature-gate.rs:46:55
+error: expected expression, found `let` statement
+  --> $DIR/feature-gate.rs:34:55
    |
 LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
    |                                                       ^^^^^^^^^
    |
    = note: only supported directly in conditions of `if` and `while` expressions
 note: `let`s wrapped in parentheses are not supported in a context with let chains
-  --> $DIR/feature-gate.rs:46:42
+  --> $DIR/feature-gate.rs:34:42
    |
 LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
    |                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: `let` expressions are not supported here
-  --> $DIR/feature-gate.rs:46:68
+error: expected expression, found `let` statement
+  --> $DIR/feature-gate.rs:34:68
    |
 LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
    |                                                                    ^^^^^^^^^
    |
    = note: only supported directly in conditions of `if` and `while` expressions
 note: `let`s wrapped in parentheses are not supported in a context with let chains
-  --> $DIR/feature-gate.rs:46:42
+  --> $DIR/feature-gate.rs:34:42
    |
 LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
    |                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: `let` expressions are not supported here
-  --> $DIR/feature-gate.rs:78:16
+error: expected expression, found `let` statement
+  --> $DIR/feature-gate.rs:60:16
    |
 LL |     use_expr!((let 0 = 1 && 0 == 0));
-   |                ^^^^^^^^^
+   |                ^^^
    |
    = note: only supported directly in conditions of `if` and `while` expressions
-note: `let`s wrapped in parentheses are not supported in a context with let chains
-  --> $DIR/feature-gate.rs:78:16
-   |
-LL |     use_expr!((let 0 = 1 && 0 == 0));
-   |                ^^^^^^^^^^^^^^^^^^^
 
-error: `let` expressions are not supported here
-  --> $DIR/feature-gate.rs:82:16
+error: expected expression, found `let` statement
+  --> $DIR/feature-gate.rs:62:16
    |
 LL |     use_expr!((let 0 = 1));
-   |                ^^^^^^^^^
+   |                ^^^
    |
    = note: only supported directly in conditions of `if` and `while` expressions
-note: `let`s wrapped in parentheses are not supported in a context with let chains
-  --> $DIR/feature-gate.rs:82:16
+
+error: no rules expected the token `let`
+  --> $DIR/feature-gate.rs:70:15
    |
-LL |     use_expr!((let 0 = 1));
-   |                ^^^^^^^^^
+LL |     macro_rules! use_expr {
+   |     --------------------- when calling this macro
+...
+LL |     use_expr!(let 0 = 1);
+   |               ^^^ no rules expected this token in macro call
+   |
+note: while trying to match meta-variable `$e:expr`
+  --> $DIR/feature-gate.rs:53:10
+   |
+LL |         ($e:expr) => {
+   |          ^^^^^^^
 
 error[E0658]: `if let` guards are experimental
   --> $DIR/feature-gate.rs:7:12
@@ -233,7 +157,7 @@ LL |         () if let 0 = 1 => {}
    = help: you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`
 
 error[E0658]: `if let` guards are experimental
-  --> $DIR/feature-gate.rs:20:12
+  --> $DIR/feature-gate.rs:16:12
    |
 LL |         () if true && let 0 = 1 => {}
    |            ^^^^^^^^^^^^^^^^^^^^
@@ -243,7 +167,7 @@ LL |         () if true && let 0 = 1 => {}
    = help: you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`
 
 error[E0658]: `if let` guards are experimental
-  --> $DIR/feature-gate.rs:24:12
+  --> $DIR/feature-gate.rs:20:12
    |
 LL |         () if let 0 = 1 && true => {}
    |            ^^^^^^^^^^^^^^^^^^^^
@@ -253,7 +177,7 @@ LL |         () if let 0 = 1 && true => {}
    = help: you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`
 
 error[E0658]: `if let` guards are experimental
-  --> $DIR/feature-gate.rs:46:12
+  --> $DIR/feature-gate.rs:34:12
    |
 LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -263,7 +187,7 @@ LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 =
    = help: you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`
 
 error[E0658]: `if let` guards are experimental
-  --> $DIR/feature-gate.rs:61:12
+  --> $DIR/feature-gate.rs:43:12
    |
 LL |         () if let Range { start: _, end: _ } = (true..true) && false => {}
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -273,7 +197,7 @@ LL |         () if let Range { start: _, end: _ } = (true..true) && false => {}
    = help: you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`
 
 error[E0658]: `if let` guards are experimental
-  --> $DIR/feature-gate.rs:88:12
+  --> $DIR/feature-gate.rs:66:12
    |
 LL |         () if let 0 = 1 => {}
    |            ^^^^^^^^^^^^
@@ -283,25 +207,7 @@ LL |         () if let 0 = 1 => {}
    = help: you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`
 
 error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:10:16
-   |
-LL |         () if (let 0 = 1) => {}
-   |                ^^^^^^^^^
-   |
-   = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
-   = help: add `#![feature(let_chains)]` to the crate attributes to enable
-
-error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:15:18
-   |
-LL |         () if (((let 0 = 1))) => {}
-   |                  ^^^^^^^^^
-   |
-   = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
-   = help: add `#![feature(let_chains)]` to the crate attributes to enable
-
-error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:20:23
+  --> $DIR/feature-gate.rs:16:23
    |
 LL |         () if true && let 0 = 1 => {}
    |                       ^^^^^^^^^
@@ -310,7 +216,7 @@ LL |         () if true && let 0 = 1 => {}
    = help: add `#![feature(let_chains)]` to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:24:15
+  --> $DIR/feature-gate.rs:20:15
    |
 LL |         () if let 0 = 1 && true => {}
    |               ^^^^^^^^^
@@ -319,43 +225,7 @@ LL |         () if let 0 = 1 && true => {}
    = help: add `#![feature(let_chains)]` to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:28:16
-   |
-LL |         () if (let 0 = 1) && true => {}
-   |                ^^^^^^^^^
-   |
-   = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
-   = help: add `#![feature(let_chains)]` to the crate attributes to enable
-
-error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:33:24
-   |
-LL |         () if true && (let 0 = 1) => {}
-   |                        ^^^^^^^^^
-   |
-   = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
-   = help: add `#![feature(let_chains)]` to the crate attributes to enable
-
-error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:38:16
-   |
-LL |         () if (let 0 = 1) && (let 0 = 1) => {}
-   |                ^^^^^^^^^
-   |
-   = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
-   = help: add `#![feature(let_chains)]` to the crate attributes to enable
-
-error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:38:31
-   |
-LL |         () if (let 0 = 1) && (let 0 = 1) => {}
-   |                               ^^^^^^^^^
-   |
-   = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
-   = help: add `#![feature(let_chains)]` to the crate attributes to enable
-
-error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:46:15
+  --> $DIR/feature-gate.rs:34:15
    |
 LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
    |               ^^^^^^^^^
@@ -364,7 +234,7 @@ LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 =
    = help: add `#![feature(let_chains)]` to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:46:28
+  --> $DIR/feature-gate.rs:34:28
    |
 LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
    |                            ^^^^^^^^^
@@ -373,34 +243,7 @@ LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 =
    = help: add `#![feature(let_chains)]` to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:46:42
-   |
-LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
-   |                                          ^^^^^^^^^
-   |
-   = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
-   = help: add `#![feature(let_chains)]` to the crate attributes to enable
-
-error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:46:55
-   |
-LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
-   |                                                       ^^^^^^^^^
-   |
-   = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
-   = help: add `#![feature(let_chains)]` to the crate attributes to enable
-
-error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:46:68
-   |
-LL |         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
-   |                                                                    ^^^^^^^^^
-   |
-   = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
-   = help: add `#![feature(let_chains)]` to the crate attributes to enable
-
-error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:61:15
+  --> $DIR/feature-gate.rs:43:15
    |
 LL |         () if let Range { start: _, end: _ } = (true..true) && false => {}
    |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -408,24 +251,6 @@ LL |         () if let Range { start: _, end: _ } = (true..true) && false => {}
    = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
    = help: add `#![feature(let_chains)]` to the crate attributes to enable
 
-error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:78:16
-   |
-LL |     use_expr!((let 0 = 1 && 0 == 0));
-   |                ^^^^^^^^^
-   |
-   = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
-   = help: add `#![feature(let_chains)]` to the crate attributes to enable
-
-error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:82:16
-   |
-LL |     use_expr!((let 0 = 1));
-   |                ^^^^^^^^^
-   |
-   = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
-   = help: add `#![feature(let_chains)]` to the crate attributes to enable
-
-error: aborting due to 45 previous errors
+error: aborting due to 23 previous errors
 
 For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/guard-lifetime-1.rs b/tests/ui/rfcs/rfc-2294-if-let-guard/guard-lifetime-1.rs
new file mode 100644
index 000000000..792225e65
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/guard-lifetime-1.rs
@@ -0,0 +1,15 @@
+// References to by-move bindings in an if-let guard *cannot* be used after the guard.
+
+#![feature(if_let_guard)]
+
+fn main() {
+    let x: Option<Option<String>> = Some(Some(String::new()));
+    match x {
+        Some(mut y) if let Some(ref z) = y => {
+            //~^ ERROR: cannot move out of `x.0` because it is borrowed
+            let _z: &String = z;
+            let _y: Option<String> = y;
+        }
+        _ => {}
+    }
+}
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/guard-lifetime-1.stderr b/tests/ui/rfcs/rfc-2294-if-let-guard/guard-lifetime-1.stderr
new file mode 100644
index 000000000..b8e1bb324
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/guard-lifetime-1.stderr
@@ -0,0 +1,15 @@
+error[E0505]: cannot move out of `x.0` because it is borrowed
+  --> $DIR/guard-lifetime-1.rs:8:14
+   |
+LL |         Some(mut y) if let Some(ref z) = y => {
+   |              ^^^^^
+   |              |
+   |              move out of `x.0` occurs here
+   |              borrow of `x.0` occurs here
+LL |
+LL |             let _z: &String = z;
+   |                               - borrow later used here
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0505`.
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/guard-lifetime-2.rs b/tests/ui/rfcs/rfc-2294-if-let-guard/guard-lifetime-2.rs
new file mode 100644
index 000000000..aa2154e3e
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/guard-lifetime-2.rs
@@ -0,0 +1,16 @@
+// References to by-mutable-ref bindings in an if-let guard *can* be used after the guard.
+
+// check-pass
+
+#![feature(if_let_guard)]
+
+fn main() {
+    let mut x: Option<Option<String>> = Some(Some(String::new()));
+    match x {
+        Some(ref mut y) if let Some(ref z) = *y => {
+            let _z: &String = z;
+            let _y: &mut Option<String> = y;
+        }
+        _ => {}
+    }
+}
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/guard-mutability-1.rs b/tests/ui/rfcs/rfc-2294-if-let-guard/guard-mutability-1.rs
new file mode 100644
index 000000000..9353c9d92
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/guard-mutability-1.rs
@@ -0,0 +1,14 @@
+// Check mutable bindings cannot be mutated by an if-let guard.
+
+#![feature(if_let_guard)]
+
+fn main() {
+    let x: Option<Option<i32>> = Some(Some(6));
+    match x {
+        Some(mut y) if let Some(ref mut z) = y => {
+            //~^ ERROR cannot borrow `y.0` as mutable, as it is immutable for the pattern guard
+            let _: &mut i32 = z;
+        }
+        _ => {}
+    }
+}
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/guard-mutability-1.stderr b/tests/ui/rfcs/rfc-2294-if-let-guard/guard-mutability-1.stderr
new file mode 100644
index 000000000..009d15338
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/guard-mutability-1.stderr
@@ -0,0 +1,11 @@
+error[E0596]: cannot borrow `y.0` as mutable, as it is immutable for the pattern guard
+  --> $DIR/guard-mutability-1.rs:8:33
+   |
+LL |         Some(mut y) if let Some(ref mut z) = y => {
+   |                                 ^^^^^^^^^ cannot borrow as mutable
+   |
+   = note: variables bound in patterns are immutable until the end of the pattern guard
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0596`.
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/guard-mutability-2.rs b/tests/ui/rfcs/rfc-2294-if-let-guard/guard-mutability-2.rs
new file mode 100644
index 000000000..4efa02f57
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/guard-mutability-2.rs
@@ -0,0 +1,14 @@
+// Check mutable reference bindings cannot be mutated by an if-let guard.
+
+#![feature(if_let_guard)]
+
+fn main() {
+    let mut x: Option<Option<i32>> = Some(Some(6));
+    match x {
+        Some(ref mut y) if let Some(ref mut z) = *y => {
+            //~^ ERROR cannot borrow `y.0` as mutable, as it is immutable for the pattern guard
+            let _: &mut i32 = z;
+        }
+        _ => {}
+    }
+}
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/guard-mutability-2.stderr b/tests/ui/rfcs/rfc-2294-if-let-guard/guard-mutability-2.stderr
new file mode 100644
index 000000000..07e7c6a2c
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/guard-mutability-2.stderr
@@ -0,0 +1,11 @@
+error[E0596]: cannot borrow `y.0` as mutable, as it is immutable for the pattern guard
+  --> $DIR/guard-mutability-2.rs:8:37
+   |
+LL |         Some(ref mut y) if let Some(ref mut z) = *y => {
+   |                                     ^^^^^^^^^ cannot borrow as mutable
+   |
+   = note: variables bound in patterns are immutable until the end of the pattern guard
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0596`.
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/macro-expanded.rs b/tests/ui/rfcs/rfc-2294-if-let-guard/macro-expanded.rs
new file mode 100644
index 000000000..423a2cd53
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/macro-expanded.rs
@@ -0,0 +1,16 @@
+// Expression macros can't expand to a let match guard.
+
+#![feature(if_let_guard)]
+#![feature(let_chains)]
+
+macro_rules! m {
+    ($e:expr) => { let Some(x) = $e }
+    //~^ ERROR expected expression, found `let` statement
+}
+
+fn main() {
+    match () {
+        () if m!(Some(5)) => {}
+        _ => {}
+    }
+}
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/macro-expanded.stderr b/tests/ui/rfcs/rfc-2294-if-let-guard/macro-expanded.stderr
new file mode 100644
index 000000000..00c1c303d
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/macro-expanded.stderr
@@ -0,0 +1,14 @@
+error: expected expression, found `let` statement
+  --> $DIR/macro-expanded.rs:7:20
+   |
+LL |     ($e:expr) => { let Some(x) = $e }
+   |                    ^^^
+...
+LL |         () if m!(Some(5)) => {}
+   |               ----------- in this macro invocation
+   |
+   = note: only supported directly in conditions of `if` and `while` expressions
+   = note: this error originates in the macro `m` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to previous error
+
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/move-guard-if-let-chain.rs b/tests/ui/rfcs/rfc-2294-if-let-guard/move-guard-if-let-chain.rs
new file mode 100644
index 000000000..5c333cd77
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/move-guard-if-let-chain.rs
@@ -0,0 +1,97 @@
+#![feature(if_let_guard)]
+#![feature(let_chains)]
+#![allow(irrefutable_let_patterns)]
+
+fn same_pattern(c: bool) {
+    let x: Box<_> = Box::new(1);
+
+    let v = (1, 2);
+
+    match v {
+        (1, 2) if let y = x && c => (),
+        (1, 2) if let z = x => (), //~ ERROR use of moved value: `x`
+        _ => (),
+    }
+}
+
+fn same_pattern_ok(c: bool) {
+    let x: Box<_> = Box::new(1);
+
+    let v = (1, 2);
+
+    match v {
+        (1, 2) if c && let y = x => (),
+        (1, 2) if let z = x => (),
+        _ => (),
+    }
+}
+
+fn different_patterns(c: bool) {
+    let x: Box<_> = Box::new(1);
+
+    let v = (1, 2);
+
+    match v {
+        (1, _) if let y = x && c => (),
+        (_, 2) if let z = x => (), //~ ERROR use of moved value: `x`
+        _ => (),
+    }
+}
+
+fn different_patterns_ok(c: bool) {
+    let x: Box<_> = Box::new(1);
+
+    let v = (1, 2);
+
+    match v {
+        (1, _) if c && let y = x => (),
+        (_, 2) if let z = x => (),
+        _ => (),
+    }
+}
+
+fn or_pattern(c: bool) {
+    let x: Box<_> = Box::new(1);
+
+    let v = (1, 2);
+
+    match v {
+        (1, _) | (_, 2) if let y = x && c => (), //~ ERROR use of moved value: `x`
+        _ => (),
+    }
+}
+
+fn or_pattern_ok(c: bool) {
+    let x: Box<_> = Box::new(1);
+
+    let v = (1, 2);
+
+    match v {
+        (1, _) | (_, 2) if c && let y = x => (),
+        _ => (),
+    }
+}
+
+fn use_in_arm(c: bool) {
+    let x: Box<_> = Box::new(1);
+
+    let v = (1, 2);
+
+    match v {
+        (1, 2) if let y = x && c => false,
+        _ => { *x == 1 }, //~ ERROR use of moved value: `x`
+    };
+}
+
+fn use_in_arm_ok(c: bool) {
+    let x: Box<_> = Box::new(1);
+
+    let v = (1, 2);
+
+    match v {
+        (1, 2) if c && let y = x => false,
+        _ => { *x == 1 },
+    };
+}
+
+fn main() {}
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/move-guard-if-let-chain.stderr b/tests/ui/rfcs/rfc-2294-if-let-guard/move-guard-if-let-chain.stderr
new file mode 100644
index 000000000..d27fde582
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/move-guard-if-let-chain.stderr
@@ -0,0 +1,67 @@
+error[E0382]: use of moved value: `x`
+  --> $DIR/move-guard-if-let-chain.rs:12:27
+   |
+LL |     let x: Box<_> = Box::new(1);
+   |         - move occurs because `x` has type `Box<i32>`, which does not implement the `Copy` trait
+...
+LL |         (1, 2) if let y = x && c => (),
+   |                       - value moved here
+LL |         (1, 2) if let z = x => (),
+   |                           ^ value used here after move
+   |
+help: borrow this binding in the pattern to avoid moving the value
+   |
+LL |         (1, 2) if let ref y = x && c => (),
+   |                       +++
+
+error[E0382]: use of moved value: `x`
+  --> $DIR/move-guard-if-let-chain.rs:36:27
+   |
+LL |     let x: Box<_> = Box::new(1);
+   |         - move occurs because `x` has type `Box<i32>`, which does not implement the `Copy` trait
+...
+LL |         (1, _) if let y = x && c => (),
+   |                       - value moved here
+LL |         (_, 2) if let z = x => (),
+   |                           ^ value used here after move
+   |
+help: borrow this binding in the pattern to avoid moving the value
+   |
+LL |         (1, _) if let ref y = x && c => (),
+   |                       +++
+
+error[E0382]: use of moved value: `x`
+  --> $DIR/move-guard-if-let-chain.rs:59:36
+   |
+LL |     let x: Box<_> = Box::new(1);
+   |         - move occurs because `x` has type `Box<i32>`, which does not implement the `Copy` trait
+...
+LL |         (1, _) | (_, 2) if let y = x && c => (),
+   |                                -   ^ value used here after move
+   |                                |
+   |                                value moved here
+   |
+help: borrow this binding in the pattern to avoid moving the value
+   |
+LL |         (1, _) | (_, 2) if let ref y = x && c => (),
+   |                                +++
+
+error[E0382]: use of moved value: `x`
+  --> $DIR/move-guard-if-let-chain.rs:82:16
+   |
+LL |     let x: Box<_> = Box::new(1);
+   |         - move occurs because `x` has type `Box<i32>`, which does not implement the `Copy` trait
+...
+LL |         (1, 2) if let y = x && c => false,
+   |                       - value moved here
+LL |         _ => { *x == 1 },
+   |                ^^ value used here after move
+   |
+help: borrow this binding in the pattern to avoid moving the value
+   |
+LL |         (1, 2) if let ref y = x && c => false,
+   |                       +++
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0382`.
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/move-guard-if-let.rs b/tests/ui/rfcs/rfc-2294-if-let-guard/move-guard-if-let.rs
new file mode 100644
index 000000000..071b86e2e
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/move-guard-if-let.rs
@@ -0,0 +1,41 @@
+// Check that borrowck knows that moves in the pattern for if-let guards
+// only happen when the pattern is matched.
+
+// build-pass
+
+#![feature(if_let_guard)]
+#![allow(irrefutable_let_patterns)]
+
+fn same_pattern() {
+    let x: Box<_> = Box::new(1);
+
+    let v = (1, 2);
+
+    match v {
+        (1, 2) if let y = x => (),
+        (1, 2) if let z = x => (),
+        _ => (),
+    }
+}
+
+fn or_pattern() {
+    let x: Box<_> = Box::new(1);
+
+    let v = (1, 2);
+
+    match v {
+        (1, _) | (_, 2) if let y = x => (),
+        _ => (),
+    }
+}
+
+fn main() {
+    let x: Box<_> = Box::new(1);
+
+    let v = (1, 2);
+
+    match v {
+        (1, 2) if let y = x => false,
+        _ => { *x == 1 },
+    };
+}
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/parens.rs b/tests/ui/rfcs/rfc-2294-if-let-guard/parens.rs
new file mode 100644
index 000000000..f12824db9
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/parens.rs
@@ -0,0 +1,25 @@
+// Parenthesised let "expressions" are not allowed in guards
+
+#![feature(if_let_guard)]
+#![feature(let_chains)]
+
+#[cfg(FALSE)]
+fn un_cfged() {
+    match () {
+        () if let 0 = 1 => {}
+        () if (let 0 = 1) => {}
+        //~^ ERROR expected expression, found `let` statement
+        () if (((let 0 = 1))) => {}
+        //~^ ERROR expected expression, found `let` statement
+    }
+}
+
+fn main() {
+    match () {
+        () if let 0 = 1 => {}
+        () if (let 0 = 1) => {}
+        //~^ ERROR expected expression, found `let` statement
+        () if (((let 0 = 1))) => {}
+        //~^ ERROR expected expression, found `let` statement
+    }
+}
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/parens.stderr b/tests/ui/rfcs/rfc-2294-if-let-guard/parens.stderr
new file mode 100644
index 000000000..0c16d9c54
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/parens.stderr
@@ -0,0 +1,54 @@
+error: expected expression, found `let` statement
+  --> $DIR/parens.rs:10:16
+   |
+LL |         () if (let 0 = 1) => {}
+   |                ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if` and `while` expressions
+note: `let`s wrapped in parentheses are not supported in a context with let chains
+  --> $DIR/parens.rs:10:16
+   |
+LL |         () if (let 0 = 1) => {}
+   |                ^^^^^^^^^
+
+error: expected expression, found `let` statement
+  --> $DIR/parens.rs:12:18
+   |
+LL |         () if (((let 0 = 1))) => {}
+   |                  ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if` and `while` expressions
+note: `let`s wrapped in parentheses are not supported in a context with let chains
+  --> $DIR/parens.rs:12:18
+   |
+LL |         () if (((let 0 = 1))) => {}
+   |                  ^^^^^^^^^
+
+error: expected expression, found `let` statement
+  --> $DIR/parens.rs:20:16
+   |
+LL |         () if (let 0 = 1) => {}
+   |                ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if` and `while` expressions
+note: `let`s wrapped in parentheses are not supported in a context with let chains
+  --> $DIR/parens.rs:20:16
+   |
+LL |         () if (let 0 = 1) => {}
+   |                ^^^^^^^^^
+
+error: expected expression, found `let` statement
+  --> $DIR/parens.rs:22:18
+   |
+LL |         () if (((let 0 = 1))) => {}
+   |                  ^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if` and `while` expressions
+note: `let`s wrapped in parentheses are not supported in a context with let chains
+  --> $DIR/parens.rs:22:18
+   |
+LL |         () if (((let 0 = 1))) => {}
+   |                  ^^^^^^^^^
+
+error: aborting due to 4 previous errors
+
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/partially-macro-expanded.rs b/tests/ui/rfcs/rfc-2294-if-let-guard/partially-macro-expanded.rs
new file mode 100644
index 000000000..d91b3a358
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/partially-macro-expanded.rs
@@ -0,0 +1,18 @@
+// Macros can be used for (parts of) the pattern and expression in an if let guard
+// check-pass
+
+#![feature(if_let_guard)]
+#![feature(let_chains)]
+
+macro_rules! m {
+    (pattern $i:ident) => { Some($i) };
+    (expression $e:expr) => { $e };
+}
+
+fn main() {
+    match () {
+        () if let m!(pattern x) = m!(expression Some(4)) => {}
+        () if let [m!(pattern y)] = [Some(8 + m!(expression 4))] => {}
+        _ => {}
+    }
+}
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/shadowing.rs b/tests/ui/rfcs/rfc-2294-if-let-guard/shadowing.rs
new file mode 100644
index 000000000..dba292ef9
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/shadowing.rs
@@ -0,0 +1,23 @@
+// Check shadowing in if let guards works as expected.
+// check-pass
+
+#![feature(if_let_guard)]
+#![feature(let_chains)]
+
+fn main() {
+    let x: Option<Option<i32>> = Some(Some(6));
+    match x {
+        Some(x) if let Some(x) = x => {
+            let _: i32 = x;
+        }
+        _ => {}
+    }
+
+    let y: Option<Option<Option<i32>>> = Some(Some(Some(-24)));
+    match y {
+        Some(y) if let Some(y) = y && let Some(y) = y => {
+            let _: i32 = y;
+        }
+        _ => {}
+    }
+}
diff --git a/tests/ui/rfcs/rfc-2294-if-let-guard/type-inference.rs b/tests/ui/rfcs/rfc-2294-if-let-guard/type-inference.rs
new file mode 100644
index 000000000..ef7a772e6
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2294-if-let-guard/type-inference.rs
@@ -0,0 +1,16 @@
+// check-pass
+
+#![feature(if_let_guard)]
+
+struct S;
+
+fn get<T>() -> Option<T> {
+    None
+}
+
+fn main() {
+    match get() {
+        x if let Some(S) = x => {}
+        _ => {}
+    }
+}