Rollup merge of #95008 - c410-f3r:let-chains-paren, r=wesleywiser

[`let_chains`] Forbid `let` inside parentheses

Parenthesizes are mostly a no-op in let chains, in other words, they are mostly ignored.

```rust
let opt = Some(Some(1i32));

if (let Some(a) = opt && (let Some(b) = a)) && b == 1 {
    println!("`b` is declared inside but used outside");
}
```

As seen above, such behavior can lead to confusion.

A proper fix or nested encapsulation would probably require research, time and a modified MIR graph so in this PR I simply denied any `let` inside parentheses. Non-let stuff are still allowed.

```rust
fn main() {
    let fun = || true;

    if let true = (true && fun()) && (true) {
        println!("Allowed");
    }
}
```

It is worth noting that `let ...`  is not an expression and the RFC did not mention this specific situation.

cc `@matthewjasper`

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -120,12 +120,21 @@ impl<'a> AstValidator<'a> {
             let err = "`let` expressions are not supported here";
             let mut diag = sess.struct_span_err(expr.span, err);
             diag.note("only supported directly in conditions of `if` and `while` expressions");
-            diag.note("as well as when nested within `&&` and parentheses in those conditions");
+            match forbidden_let_reason {
-            if let ForbiddenLetReason::ForbiddenWithOr(span) = forbidden_let_reason {
+                ForbiddenLetReason::GenericForbidden => {}
-                diag.span_note(
+                ForbiddenLetReason::NotSupportedOr(span) => {
-                    span,
+                    diag.span_note(
-                    "`||` operators are not currently supported in let chain expressions",
+                        span,
-                );
+                        "`||` operators are not supported in let chain expressions",
+                    );
+                }
+                ForbiddenLetReason::NotSupportedParentheses(span) => {
+                    diag.span_note(
+                        span,
+                        "`let`s wrapped in parentheses are not supported in a context with let \
+                        chains",
+                    );
+                }
             }
             diag.emit();
         } else {
@@ -1009,9 +1018,9 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
         self.with_let_management(Some(ForbiddenLetReason::GenericForbidden), |this, forbidden_let_reason| {
             match &expr.kind {
                 ExprKind::Binary(Spanned { node: BinOpKind::Or, span }, lhs, rhs) => {
-                    let forbidden_let_reason = Some(ForbiddenLetReason::ForbiddenWithOr(*span));
+                    let local_reason = Some(ForbiddenLetReason::NotSupportedOr(*span));
-                    this.with_let_management(forbidden_let_reason, |this, _| this.visit_expr(lhs));
+                    this.with_let_management(local_reason, |this, _| this.visit_expr(lhs));
-                    this.with_let_management(forbidden_let_reason, |this, _| this.visit_expr(rhs));
+                    this.with_let_management(local_reason, |this, _| this.visit_expr(rhs));
                 }
                 ExprKind::If(cond, then, opt_else) => {
                     this.visit_block(then);
@@ -1036,7 +1045,23 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                         }
                     }
                 }
-                ExprKind::Paren(_) | ExprKind::Binary(Spanned { node: BinOpKind::And, .. }, ..) => {
+                ExprKind::Paren(local_expr) => {
+                    fn has_let_expr(expr: &Expr) -> bool {
+                        match expr.kind {
+                            ExprKind::Binary(_, ref lhs, ref rhs) => has_let_expr(lhs) || has_let_expr(rhs),
+                            ExprKind::Let(..) => true,
+                            _ => false,
+                        }
+                    }
+                    let local_reason = if has_let_expr(local_expr) {
+                        Some(ForbiddenLetReason::NotSupportedParentheses(local_expr.span))
+                    }
+                    else {
+                        forbidden_let_reason
+                    };
+                    this.with_let_management(local_reason, |this, _| this.visit_expr(local_expr));
+                }
+                ExprKind::Binary(Spanned { node: BinOpKind::And, .. }, ..) => {
                     this.with_let_management(forbidden_let_reason, |this, _| visit::walk_expr(this, expr));
                     return;
                 }
@@ -1810,8 +1835,13 @@ pub fn check_crate(session: &Session, krate: &Crate, lints: &mut LintBuffer) ->
 /// Used to forbid `let` expressions in certain syntactic locations.
 #[derive(Clone, Copy)]
 enum ForbiddenLetReason {
-    /// A let chain with the `||` operator
-    ForbiddenWithOr(Span),
     /// `let` is not valid and the source environment is not important
     GenericForbidden,
+    /// A let chain with the `||` operator
+    NotSupportedOr(Span),
+    /// A let chain with invalid parentheses
+    ///
+    /// For exemple, `let 1 = 1 && (expr && expr)` is allowed
+    /// but `(let 1 = 1 && (let 1 = 1 && (let 1 = 1))) && let a = 1` is not
+    NotSupportedParentheses(Span),
 }

src/test/ui/rfc-2497-if-let-chains/disallowed-positions.rs

@@ -25,6 +25,67 @@ use std::ops::Range;
 
 fn main() {}
 
+fn _if() {
+    if (let 0 = 1) {}
+    //~^ ERROR `let` expressions are not supported here
+
+    if (((let 0 = 1))) {}
+    //~^ ERROR `let` expressions are not supported here
+
+    if (let 0 = 1) && true {}
+    //~^ ERROR `let` expressions are not supported here
+
+    if true && (let 0 = 1) {}
+    //~^ ERROR `let` expressions are not supported here
+
+    if (let 0 = 1) && (let 0 = 1) {}
+    //~^ 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 `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
+}
+
+fn _while() {
+    while (let 0 = 1) {}
+    //~^ ERROR `let` expressions are not supported here
+
+    while (((let 0 = 1))) {}
+    //~^ ERROR `let` expressions are not supported here
+
+    while (let 0 = 1) && true {}
+    //~^ ERROR `let` expressions are not supported here
+
+    while true && (let 0 = 1) {}
+    //~^ ERROR `let` expressions are not supported here
+
+    while (let 0 = 1) && (let 0 = 1) {}
+    //~^ ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
+
+    while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
+    //~^ ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
+}
+
+fn _macros() {
+    macro_rules! use_expr {
+        ($e:expr) => {
+            if $e {}
+            while $e {}
+        }
+    }
+    use_expr!((let 0 = 1 && 0 == 0));
+    //~^ ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
+    use_expr!((let 0 = 1));
+    //~^ ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
+}
+
 fn nested_within_if_expr() {
     if &let 0 = 0 {} //~ ERROR `let` expressions are not supported here
     //~^ ERROR mismatched types
@@ -234,3 +295,44 @@ fn inside_const_generic_arguments() {
         //~| ERROR  expressions must be enclosed in braces
     >::O == 5 {}
 }
+
+fn with_parenthesis() {
+    let opt = Some(Some(1i32));
+
+    if (let Some(a) = opt && true) {
+    //~^ ERROR `let` expressions are not supported here
+    }
+
+    if (let Some(a) = opt) && true {
+    //~^ ERROR `let` expressions are not supported here
+    }
+    if (let Some(a) = opt) && (let Some(b) = a) {
+    //~^ ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
+    }
+    if let Some(a) = opt && (true && true) {
+    }
+
+    if (let Some(a) = opt && (let Some(b) = a)) && b == 1 {
+    //~^ ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
+    }
+    if (let Some(a) = opt && (let Some(b) = a)) && true {
+    //~^ ERROR `let` expressions are not supported here
+    //~| ERROR `let` expressions are not supported here
+    }
+    if (let Some(a) = opt && (true)) && true {
+    //~^ ERROR `let` expressions are not supported here
+    }
+
+    if (true && (true)) && let Some(a) = opt {
+    }
+    if (true) && let Some(a) = opt {
+    }
+    if true && let Some(a) = opt {
+    }
+
+    let fun = || true;
+    if let true = (true && fun()) && (true) {
+    }
+}

src/test/ui/rfc-2497-if-let-chains/ensure-that-let-else-does-not-interact-with-let-chains.stderr

@@ -72,7 +72,6 @@ LL |     let Some(n) = opt && let another = n else {
    |                          ^^^^^^^^^^^^^^^
    |
    = note: only supported directly in conditions of `if` and `while` expressions
-   = note: as well as when nested within `&&` and parentheses in those conditions
 
 error[E0308]: mismatched types
   --> $DIR/ensure-that-let-else-does-not-interact-with-let-chains.rs:9:19

src/test/ui/rfc-2497-if-let-chains/feature-gate.rs

@@ -11,35 +11,12 @@ use std::ops::Range;
 fn _if() {
     if let 0 = 1 {} // Stable!
 
-    if (let 0 = 1) {}
-    //~^ ERROR `let` expressions in this position are unstable [E0658]
-
-    if (((let 0 = 1))) {}
-    //~^ ERROR `let` expressions in this position are unstable [E0658]
-
     if true && let 0 = 1 {}
     //~^ ERROR `let` expressions in this position are unstable [E0658]
 
     if let 0 = 1 && true {}
     //~^ ERROR `let` expressions in this position are unstable [E0658]
 
-    if (let 0 = 1) && true {}
-    //~^ ERROR `let` expressions in this position are unstable [E0658]
-
-    if true && (let 0 = 1) {}
-    //~^ ERROR `let` expressions in this position are unstable [E0658]
-
-    if (let 0 = 1) && (let 0 = 1) {}
-    //~^ ERROR `let` expressions in this position are unstable [E0658]
-    //~| ERROR `let` expressions in this position are unstable [E0658]
-
-    if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
-    //~^ ERROR `let` expressions in this position are unstable [E0658]
-    //~| ERROR `let` expressions in this position are unstable [E0658]
-    //~| ERROR `let` expressions in this position are unstable [E0658]
-    //~| ERROR `let` expressions in this position are unstable [E0658]
-    //~| ERROR `let` expressions in this position are unstable [E0658]
-
     if let Range { start: _, end: _ } = (true..true) && false {}
     //~^ ERROR `let` expressions in this position are unstable [E0658]
 }
@@ -47,35 +24,12 @@ fn _if() {
 fn _while() {
     while let 0 = 1 {} // Stable!
 
-    while (let 0 = 1) {}
-    //~^ ERROR `let` expressions in this position are unstable [E0658]
-
-    while (((let 0 = 1))) {}
-    //~^ ERROR `let` expressions in this position are unstable [E0658]
-
     while true && let 0 = 1 {}
     //~^ ERROR `let` expressions in this position are unstable [E0658]
 
     while let 0 = 1 && true {}
     //~^ ERROR `let` expressions in this position are unstable [E0658]
 
-    while (let 0 = 1) && true {}
-    //~^ ERROR `let` expressions in this position are unstable [E0658]
-
-    while true && (let 0 = 1) {}
-    //~^ ERROR `let` expressions in this position are unstable [E0658]
-
-    while (let 0 = 1) && (let 0 = 1) {}
-    //~^ ERROR `let` expressions in this position are unstable [E0658]
-    //~| ERROR `let` expressions in this position are unstable [E0658]
-
-    while let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) {}
-    //~^ ERROR `let` expressions in this position are unstable [E0658]
-    //~| ERROR `let` expressions in this position are unstable [E0658]
-    //~| ERROR `let` expressions in this position are unstable [E0658]
-    //~| ERROR `let` expressions in this position are unstable [E0658]
-    //~| ERROR `let` expressions in this position are unstable [E0658]
-
     while let Range { start: _, end: _ } = (true..true) && false {}
     //~^ ERROR `let` expressions in this position are unstable [E0658]
 }
@@ -92,10 +46,6 @@ fn _macros() {
             while $e {}
         }
     }
-    use_expr!((let 0 = 1 && 0 == 0));
-    //~^ ERROR `let` expressions in this position are unstable [E0658]
-    use_expr!((let 0 = 1));
-    //~^ ERROR `let` expressions in this position are unstable [E0658]
     #[cfg(FALSE)] (let 0 = 1);
     //~^ ERROR `let` expressions in this position are unstable [E0658]
     use_expr!(let 0 = 1);

src/test/ui/rfc-2497-if-let-chains/feature-gate.stderr

@@ -1,5 +1,5 @@
 error: no rules expected the token `let`
-  --> $DIR/feature-gate.rs:101:15
+  --> $DIR/feature-gate.rs:51:15
    |
 LL |     macro_rules! use_expr {
    |     --------------------- when calling this macro
@@ -8,25 +8,7 @@ LL |     use_expr!(let 0 = 1);
    |               ^^^ no rules expected this token in macro call
 
 error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:14:9
+  --> $DIR/feature-gate.rs:14:16
-   |
-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:17:11
-   |
-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:20:16
    |
 LL |     if true && let 0 = 1 {}
    |                ^^^^^^^^^
@@ -35,7 +17,7 @@ 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:23:8
+  --> $DIR/feature-gate.rs:17:8
    |
 LL |     if let 0 = 1 && true {}
    |        ^^^^^^^^^
@@ -44,88 +26,7 @@ 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:26:9
+  --> $DIR/feature-gate.rs:20:8
-   |
-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:29:17
-   |
-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:32:9
-   |
-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:32:24
-   |
-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:36:8
-   |
-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:36:21
-   |
-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:36:35
-   |
-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:36:48
-   |
-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:36:61
-   |
-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:43:8
    |
 LL |     if let Range { start: _, end: _ } = (true..true) && false {}
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -134,25 +35,7 @@ LL |     if let Range { start: _, end: _ } = (true..true) && false {}
    = help: add `#![feature(let_chains)]` to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:50:12
+  --> $DIR/feature-gate.rs:27:19
-   |
-LL |     while (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:53:14
-   |
-LL |     while (((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:56:19
    |
 LL |     while true && let 0 = 1 {}
    |                   ^^^^^^^^^
@@ -161,7 +44,7 @@ LL |     while 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:59:11
+  --> $DIR/feature-gate.rs:30:11
    |
 LL |     while let 0 = 1 && true {}
    |           ^^^^^^^^^
@@ -170,88 +53,7 @@ LL |     while 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:62:12
+  --> $DIR/feature-gate.rs:33:11
-   |
-LL |     while (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:65:20
-   |
-LL |     while 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:68:12
-   |
-LL |     while (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:68:27
-   |
-LL |     while (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:72:11
-   |
-LL |     while 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:72:24
-   |
-LL |     while 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:72:38
-   |
-LL |     while 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:72:51
-   |
-LL |     while 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:72:64
-   |
-LL |     while 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:79:11
    |
 LL |     while let Range { start: _, end: _ } = (true..true) && false {}
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -260,7 +62,7 @@ LL |     while let Range { start: _, end: _ } = (true..true) && false {}
    = help: add `#![feature(let_chains)]` to the crate attributes to enable
 
 error[E0658]: `let` expressions in this position are unstable
-  --> $DIR/feature-gate.rs:99:20
+  --> $DIR/feature-gate.rs:49:20
    |
 LL |     #[cfg(FALSE)] (let 0 = 1);
    |                    ^^^^^^^^^
@@ -269,7 +71,7 @@ LL |     #[cfg(FALSE)] (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:86:17
+  --> $DIR/feature-gate.rs:40:17
    |
 LL |     noop_expr!((let 0 = 1));
    |                 ^^^^^^^^^
@@ -277,24 +79,6 @@ LL |     noop_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[E0658]: `let` expressions in this position are unstable
+error: aborting due to 9 previous errors
-  --> $DIR/feature-gate.rs:95:16
-   |
-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:97:16
-   |
-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 33 previous errors
 
 For more information about this error, try `rustc --explain E0658`.