Rollup merge of #82048 - mark-i-m:or-pat-type-ascription, r=petrochenkov

or-patterns: disallow in `let` bindings

~~Blocked on #81869

Disallows top-level or-patterns before type ascription. We want to reserve this syntactic space for possible future generalized type ascription.

r? ``@petrochenkov``

Author: m-ou-se

compiler/rustc_lint/src/unused.rs

@@ -872,7 +872,7 @@ impl EarlyLintPass for UnusedParens {
 
     fn check_stmt(&mut self, cx: &EarlyContext<'_>, s: &ast::Stmt) {
         if let StmtKind::Local(ref local) = s.kind {
-            self.check_unused_parens_pat(cx, &local.pat, false, false);
+            self.check_unused_parens_pat(cx, &local.pat, true, false);
         }
 
         <Self as UnusedDelimLint>::check_stmt(self, cx, s)

compiler/rustc_parse/src/parser/item.rs

@@ -1757,8 +1757,9 @@ impl<'a> Parser<'a> {
             let (pat, ty) = if is_name_required || this.is_named_param() {
                 debug!("parse_param_general parse_pat (is_name_required:{})", is_name_required);
 
-                let pat = this.parse_fn_param_pat()?;
-                if let Err(mut err) = this.expect(&token::Colon) {
+                let (pat, colon) = this.parse_fn_param_pat_colon()?;
+                if !colon {
+                    let mut err = this.unexpected::<()>().unwrap_err();
                     return if let Some(ident) =
                         this.parameter_without_type(&mut err, pat, is_name_required, first_param)
                     {

compiler/rustc_parse/src/parser/pat.rs

@@ -31,6 +31,18 @@ pub enum RecoverComma {
     No,
 }
 
+/// The result of `eat_or_separator`. We want to distinguish which case we are in to avoid
+/// emitting duplicate diagnostics.
+#[derive(Debug, Clone, Copy)]
+enum EatOrResult {
+    /// We recovered from a trailing vert.
+    TrailingVert,
+    /// We ate an `|` (or `||` and recovered).
+    AteOr,
+    /// We did not eat anything (i.e. the current token is not `|` or `||`).
+    None,
+}
+
 impl<'a> Parser<'a> {
     /// Parses a pattern.
     ///
@@ -55,9 +67,26 @@ impl<'a> Parser<'a> {
         gate_or: GateOr,
         rc: RecoverComma,
     ) -> PResult<'a, P<Pat>> {
+        self.parse_pat_allow_top_alt_inner(expected, gate_or, rc).map(|(pat, _)| pat)
+    }
+
+    /// Returns the pattern and a bool indicating whether we recovered from a trailing vert (true =
+    /// recovered).
+    fn parse_pat_allow_top_alt_inner(
+        &mut self,
+        expected: Expected,
+        gate_or: GateOr,
+        rc: RecoverComma,
+    ) -> PResult<'a, (P<Pat>, bool)> {
+        // Keep track of whether we recovered from a trailing vert so that we can avoid duplicated
+        // suggestions (which bothers rustfix).
+        //
         // Allow a '|' before the pats (RFCs 1925, 2530, and 2535).
-        let leading_vert_span =
-            if self.eat_or_separator(None) { Some(self.prev_token.span) } else { None };
+        let (leading_vert_span, mut trailing_vert) = match self.eat_or_separator(None) {
+            EatOrResult::AteOr => (Some(self.prev_token.span), false),
+            EatOrResult::TrailingVert => (None, true),
+            EatOrResult::None => (None, false),
+        };
 
         // Parse the first pattern (`p_0`).
         let first_pat = self.parse_pat_no_top_alt(expected)?;
@@ -77,16 +106,24 @@ impl<'a> Parser<'a> {
                 // If there was a leading vert, treat this as an or-pattern. This improves
                 // diagnostics.
                 let span = leading_vert_span.to(self.prev_token.span);
-                return Ok(self.mk_pat(span, PatKind::Or(vec![first_pat])));
+                return Ok((self.mk_pat(span, PatKind::Or(vec![first_pat])), trailing_vert));
             }
 
-            return Ok(first_pat);
+            return Ok((first_pat, trailing_vert));
         }
 
         // Parse the patterns `p_1 | ... | p_n` where `n > 0`.
         let lo = leading_vert_span.unwrap_or(first_pat.span);
         let mut pats = vec![first_pat];
-        while self.eat_or_separator(Some(lo)) {
+        loop {
+            match self.eat_or_separator(Some(lo)) {
+                EatOrResult::AteOr => {}
+                EatOrResult::None => break,
+                EatOrResult::TrailingVert => {
+                    trailing_vert = true;
+                    break;
+                }
+            }
             let pat = self.parse_pat_no_top_alt(expected).map_err(|mut err| {
                 err.span_label(lo, WHILE_PARSING_OR_MSG);
                 err
@@ -101,15 +138,63 @@ impl<'a> Parser<'a> {
             self.sess.gated_spans.gate(sym::or_patterns, or_pattern_span);
         }
 
-        Ok(self.mk_pat(or_pattern_span, PatKind::Or(pats)))
+        Ok((self.mk_pat(or_pattern_span, PatKind::Or(pats)), trailing_vert))
     }
 
-    /// Parse the pattern for a function or function pointer parameter.
-    pub(super) fn parse_fn_param_pat(&mut self) -> PResult<'a, P<Pat>> {
-        // We actually do _not_ allow top-level or-patterns in function params, but we use
-        // `parse_pat_allow_top_alt` anyway so that we can detect when a user tries to use it. This
-        // allows us to print a better error message.
-        //
+    /// Parse a pattern and (maybe) a `Colon` in positions where a pattern may be followed by a
+    /// type annotation (e.g. for `let` bindings or `fn` params).
+    ///
+    /// Generally, this corresponds to `pat_no_top_alt` followed by an optional `Colon`. It will
+    /// eat the `Colon` token if one is present.
+    ///
+    /// The return value represents the parsed pattern and `true` if a `Colon` was parsed (`false`
+    /// otherwise).
+    pub(super) fn parse_pat_before_ty(
+        &mut self,
+        expected: Expected,
+        gate_or: GateOr,
+        rc: RecoverComma,
+        syntax_loc: &str,
+    ) -> PResult<'a, (P<Pat>, bool)> {
+        // We use `parse_pat_allow_top_alt` regardless of whether we actually want top-level
+        // or-patterns so that we can detect when a user tries to use it. This allows us to print a
+        // better error message.
+        let (pat, trailing_vert) = self.parse_pat_allow_top_alt_inner(expected, gate_or, rc)?;
+        let colon = self.eat(&token::Colon);
+
+        if let PatKind::Or(pats) = &pat.kind {
+            let msg = format!("top-level or-patterns are not allowed in {}", syntax_loc);
+            let (help, fix) = if pats.len() == 1 {
+                // If all we have is a leading vert, then print a special message. This is the case
+                // if `parse_pat_allow_top_alt` returns an or-pattern with one variant.
+                let msg = "remove the `|`";
+                let fix = pprust::pat_to_string(&pat);
+                (msg, fix)
+            } else {
+                let msg = "wrap the pattern in parentheses";
+                let fix = format!("({})", pprust::pat_to_string(&pat));
+                (msg, fix)
+            };
+
+            if trailing_vert {
+                // We already emitted an error and suggestion to remove the trailing vert. Don't
+                // emit again.
+                self.sess.span_diagnostic.delay_span_bug(pat.span, &msg);
+            } else {
+                self.struct_span_err(pat.span, &msg)
+                    .span_suggestion(pat.span, help, fix, Applicability::MachineApplicable)
+                    .emit();
+            }
+        }
+
+        Ok((pat, colon))
+    }
+
+    /// Parse the pattern for a function or function pointer parameter, followed by a colon.
+    ///
+    /// The return value represents the parsed pattern and `true` if a `Colon` was parsed (`false`
+    /// otherwise).
+    pub(super) fn parse_fn_param_pat_colon(&mut self) -> PResult<'a, (P<Pat>, bool)> {
         // In order to get good UX, we first recover in the case of a leading vert for an illegal
         // top-level or-pat. Normally, this means recovering both `|` and `||`, but in this case,
         // a leading `||` probably doesn't indicate an or-pattern attempt, so we handle that
@@ -128,53 +213,28 @@ impl<'a> Parser<'a> {
             self.bump();
         }
 
-        let pat = self.parse_pat_allow_top_alt(PARAM_EXPECTED, GateOr::No, RecoverComma::No)?;
-
-        if let PatKind::Or(..) = &pat.kind {
-            self.ban_illegal_fn_param_or_pat(&pat);
-        }
-
-        Ok(pat)
-    }
-
-    /// Ban `A | B` immediately in a parameter pattern and suggest wrapping in parens.
-    fn ban_illegal_fn_param_or_pat(&self, pat: &Pat) {
-        // If all we have a leading vert, then print a special message. This is the case if
-        // `parse_pat_allow_top_alt` returns an or-pattern with one variant.
-        let (msg, fix) = match &pat.kind {
-            PatKind::Or(pats) if pats.len() == 1 => {
-                let msg = "remove the leading `|`";
-                let fix = pprust::pat_to_string(pat);
-                (msg, fix)
-            }
-
-            _ => {
-                let msg = "wrap the pattern in parentheses";
-                let fix = format!("({})", pprust::pat_to_string(pat));
-                (msg, fix)
-            }
-        };
-
-        self.struct_span_err(pat.span, "an or-pattern parameter must be wrapped in parentheses")
-            .span_suggestion(pat.span, msg, fix, Applicability::MachineApplicable)
-            .emit();
+        self.parse_pat_before_ty(
+            PARAM_EXPECTED,
+            GateOr::No,
+            RecoverComma::No,
+            "function parameters",
+        )
     }
 
     /// Eat the or-pattern `|` separator.
     /// If instead a `||` token is encountered, recover and pretend we parsed `|`.
-    fn eat_or_separator(&mut self, lo: Option<Span>) -> bool {
+    fn eat_or_separator(&mut self, lo: Option<Span>) -> EatOrResult {
         if self.recover_trailing_vert(lo) {
-            return false;
-        }
-
-        match self.token.kind {
-            token::OrOr => {
-                // Found `||`; Recover and pretend we parsed `|`.
-                self.ban_unexpected_or_or(lo);
-                self.bump();
-                true
-            }
-            _ => self.eat(&token::BinOp(token::Or)),
+            EatOrResult::TrailingVert
+        } else if matches!(self.token.kind, token::OrOr) {
+            // Found `||`; Recover and pretend we parsed `|`.
+            self.ban_unexpected_or_or(lo);
+            self.bump();
+            EatOrResult::AteOr
+        } else if self.eat(&token::BinOp(token::Or)) {
+            EatOrResult::AteOr
+        } else {
+            EatOrResult::None
         }
     }
 
@@ -190,14 +250,14 @@ impl<'a> Parser<'a> {
             matches!(
                 &token.uninterpolate().kind,
                 token::FatArrow // e.g. `a | => 0,`.
-            | token::Ident(kw::If, false) // e.g. `a | if expr`.
-            | token::Eq // e.g. `let a | = 0`.
-            | token::Semi // e.g. `let a |;`.
-            | token::Colon // e.g. `let a | :`.
-            | token::Comma // e.g. `let (a |,)`.
-            | token::CloseDelim(token::Bracket) // e.g. `let [a | ]`.
-            | token::CloseDelim(token::Paren) // e.g. `let (a | )`.
-            | token::CloseDelim(token::Brace) // e.g. `let A { f: a | }`.
+                | token::Ident(kw::If, false) // e.g. `a | if expr`.
+                | token::Eq // e.g. `let a | = 0`.
+                | token::Semi // e.g. `let a |;`.
+                | token::Colon // e.g. `let a | :`.
+                | token::Comma // e.g. `let (a |,)`.
+                | token::CloseDelim(token::Bracket) // e.g. `let [a | ]`.
+                | token::CloseDelim(token::Paren) // e.g. `let (a | )`.
+                | token::CloseDelim(token::Brace) // e.g. `let A { f: a | }`.
             )
         });
         match (is_end_ahead, &self.token.kind) {

compiler/rustc_parse/src/parser/stmt.rs

@@ -13,7 +13,8 @@ use rustc_ast::token::{self, TokenKind};
 use rustc_ast::util::classify;
 use rustc_ast::AstLike;
 use rustc_ast::{AttrStyle, AttrVec, Attribute, MacCall, MacCallStmt, MacStmtStyle};
-use rustc_ast::{Block, BlockCheckMode, Expr, ExprKind, Local, Stmt, StmtKind, DUMMY_NODE_ID};
+use rustc_ast::{Block, BlockCheckMode, Expr, ExprKind, Local, Stmt};
+use rustc_ast::{StmtKind, DUMMY_NODE_ID};
 use rustc_errors::{Applicability, PResult};
 use rustc_span::source_map::{BytePos, Span};
 use rustc_span::symbol::{kw, sym};
@@ -220,9 +221,10 @@ impl<'a> Parser<'a> {
     /// Parses a local variable declaration.
     fn parse_local(&mut self, attrs: AttrVec) -> PResult<'a, P<Local>> {
         let lo = self.prev_token.span;
-        let pat = self.parse_pat_allow_top_alt(None, GateOr::Yes, RecoverComma::Yes)?;
+        let (pat, colon) =
+            self.parse_pat_before_ty(None, GateOr::Yes, RecoverComma::Yes, "`let` bindings")?;
 
-        let (err, ty) = if self.eat(&token::Colon) {
+        let (err, ty) = if colon {
             // Save the state of the parser before parsing type normally, in case there is a `:`
             // instead of an `=` typo.
             let parser_snapshot_before_type = self.clone();

src/test/ui/or-patterns/already-bound-name.rs

@@ -18,28 +18,28 @@ fn main() {
     let (A(a, _) | B(a), a) = (A(0, 1), 2);
     //~^ ERROR identifier `a` is bound more than once in the same pattern
 
-    let A(a, a) | B(a) = A(0, 1);
+    let (A(a, a) | B(a)) = A(0, 1);
     //~^ ERROR identifier `a` is bound more than once in the same pattern
 
-    let B(a) | A(a, a) = A(0, 1);
+    let (B(a) | A(a, a)) = A(0, 1);
     //~^ ERROR identifier `a` is bound more than once in the same pattern
 
     match A(0, 1) {
         B(a) | A(a, a) => {} // Let's ensure `match` has no funny business.
         //~^ ERROR identifier `a` is bound more than once in the same pattern
     }
 
-    let B(A(a, _) | B(a)) | A(a, A(a, _) | B(a)) = B(B(1));
+    let (B(A(a, _) | B(a)) | A(a, A(a, _) | B(a))) = B(B(1));
     //~^ ERROR identifier `a` is bound more than once in the same pattern
     //~| ERROR identifier `a` is bound more than once in the same pattern
     //~| ERROR mismatched types
 
-    let B(_) | A(A(a, _) | B(a), A(a, _) | B(a)) = B(B(1));
+    let (B(_) | A(A(a, _) | B(a), A(a, _) | B(a))) = B(B(1));
     //~^ ERROR identifier `a` is bound more than once in the same pattern
     //~| ERROR identifier `a` is bound more than once in the same pattern
     //~| ERROR variable `a` is not bound in all patterns
 
-    let B(A(a, _) | B(a)) | A(A(a, _) | B(a), A(a, _) | B(a)) = B(B(1));
+    let (B(A(a, _) | B(a)) | A(A(a, _) | B(a), A(a, _) | B(a))) = B(B(1));
     //~^ ERROR identifier `a` is bound more than once in the same pattern
     //~| ERROR identifier `a` is bound more than once in the same pattern
 }

src/test/ui/or-patterns/already-bound-name.stderr

@@ -23,16 +23,16 @@ LL |     let (A(a, _) | B(a), a) = (A(0, 1), 2);
    |                          ^ used in a pattern more than once
 
 error[E0416]: identifier `a` is bound more than once in the same pattern
-  --> $DIR/already-bound-name.rs:21:14
+  --> $DIR/already-bound-name.rs:21:15
    |
-LL |     let A(a, a) | B(a) = A(0, 1);
-   |              ^ used in a pattern more than once
+LL |     let (A(a, a) | B(a)) = A(0, 1);
+   |               ^ used in a pattern more than once
 
 error[E0416]: identifier `a` is bound more than once in the same pattern
-  --> $DIR/already-bound-name.rs:24:21
+  --> $DIR/already-bound-name.rs:24:22
    |
-LL |     let B(a) | A(a, a) = A(0, 1);
-   |                     ^ used in a pattern more than once
+LL |     let (B(a) | A(a, a)) = A(0, 1);
+   |                      ^ used in a pattern more than once
 
 error[E0416]: identifier `a` is bound more than once in the same pattern
   --> $DIR/already-bound-name.rs:28:21
@@ -41,55 +41,55 @@ LL |         B(a) | A(a, a) => {} // Let's ensure `match` has no funny business.
    |                     ^ used in a pattern more than once
 
 error[E0416]: identifier `a` is bound more than once in the same pattern
-  --> $DIR/already-bound-name.rs:32:36
+  --> $DIR/already-bound-name.rs:32:37
    |
-LL |     let B(A(a, _) | B(a)) | A(a, A(a, _) | B(a)) = B(B(1));
-   |                                    ^ used in a pattern more than once
+LL |     let (B(A(a, _) | B(a)) | A(a, A(a, _) | B(a))) = B(B(1));
+   |                                     ^ used in a pattern more than once
 
 error[E0416]: identifier `a` is bound more than once in the same pattern
-  --> $DIR/already-bound-name.rs:32:46
+  --> $DIR/already-bound-name.rs:32:47
    |
-LL |     let B(A(a, _) | B(a)) | A(a, A(a, _) | B(a)) = B(B(1));
-   |                                              ^ used in a pattern more than once
+LL |     let (B(A(a, _) | B(a)) | A(a, A(a, _) | B(a))) = B(B(1));
+   |                                               ^ used in a pattern more than once
 
 error[E0416]: identifier `a` is bound more than once in the same pattern
-  --> $DIR/already-bound-name.rs:37:36
+  --> $DIR/already-bound-name.rs:37:37
    |
-LL |     let B(_) | A(A(a, _) | B(a), A(a, _) | B(a)) = B(B(1));
-   |                                    ^ used in a pattern more than once
+LL |     let (B(_) | A(A(a, _) | B(a), A(a, _) | B(a))) = B(B(1));
+   |                                     ^ used in a pattern more than once
 
 error[E0416]: identifier `a` is bound more than once in the same pattern
-  --> $DIR/already-bound-name.rs:37:46
+  --> $DIR/already-bound-name.rs:37:47
    |
-LL |     let B(_) | A(A(a, _) | B(a), A(a, _) | B(a)) = B(B(1));
-   |                                              ^ used in a pattern more than once
+LL |     let (B(_) | A(A(a, _) | B(a), A(a, _) | B(a))) = B(B(1));
+   |                                               ^ used in a pattern more than once
 
 error[E0408]: variable `a` is not bound in all patterns
-  --> $DIR/already-bound-name.rs:37:9
+  --> $DIR/already-bound-name.rs:37:10
    |
-LL |     let B(_) | A(A(a, _) | B(a), A(a, _) | B(a)) = B(B(1));
-   |         ^^^^ pattern doesn't bind `a`        - variable not in all patterns
+LL |     let (B(_) | A(A(a, _) | B(a), A(a, _) | B(a))) = B(B(1));
+   |          ^^^^ pattern doesn't bind `a`        - variable not in all patterns
 
 error[E0416]: identifier `a` is bound more than once in the same pattern
-  --> $DIR/already-bound-name.rs:42:49
+  --> $DIR/already-bound-name.rs:42:50
    |
-LL |     let B(A(a, _) | B(a)) | A(A(a, _) | B(a), A(a, _) | B(a)) = B(B(1));
-   |                                                 ^ used in a pattern more than once
+LL |     let (B(A(a, _) | B(a)) | A(A(a, _) | B(a), A(a, _) | B(a))) = B(B(1));
+   |                                                  ^ used in a pattern more than once
 
 error[E0416]: identifier `a` is bound more than once in the same pattern
-  --> $DIR/already-bound-name.rs:42:59
+  --> $DIR/already-bound-name.rs:42:60
    |
-LL |     let B(A(a, _) | B(a)) | A(A(a, _) | B(a), A(a, _) | B(a)) = B(B(1));
-   |                                                           ^ used in a pattern more than once
+LL |     let (B(A(a, _) | B(a)) | A(A(a, _) | B(a), A(a, _) | B(a))) = B(B(1));
+   |                                                            ^ used in a pattern more than once
 
 error[E0308]: mismatched types
-  --> $DIR/already-bound-name.rs:32:31
+  --> $DIR/already-bound-name.rs:32:32
    |
-LL |     let B(A(a, _) | B(a)) | A(a, A(a, _) | B(a)) = B(B(1));
-   |             -                 ^                    ------- this expression has type `E<E<{integer}>>`
-   |             |                 |
-   |             |                 expected integer, found enum `E`
-   |             first introduced with type `{integer}` here
+LL |     let (B(A(a, _) | B(a)) | A(a, A(a, _) | B(a))) = B(B(1));
+   |              -                 ^                     ------- this expression has type `E<E<{integer}>>`
+   |              |                 |
+   |              |                 expected integer, found enum `E`
+   |              first introduced with type `{integer}` here
    |
    = note: expected type `{integer}`
               found type `E<{integer}>`

src/test/ui/or-patterns/consistent-bindings.rs

@@ -8,9 +8,9 @@
 
 fn main() {
     // One level:
-    let Ok(a) | Err(a) = Ok(0);
-    let Ok(ref a) | Err(ref a) = Ok(0);
-    let Ok(ref mut a) | Err(ref mut a) = Ok(0);
+    let (Ok(a) | Err(a)) = Ok(0);
+    let (Ok(ref a) | Err(ref a)) = Ok(0);
+    let (Ok(ref mut a) | Err(ref mut a)) = Ok(0);
 
     // Two levels:
     enum Tri<S, T, U> {
@@ -20,10 +20,10 @@ fn main() {
     }
     use Tri::*;
 
-    let Ok((V1(a) | V2(a) | V3(a), b)) | Err(Ok((a, b)) | Err((a, b))): Result<_, Result<_, _>> =
+    let (Ok((V1(a) | V2(a) | V3(a), b)) | Err(Ok((a, b)) | Err((a, b)))): Result<_, Result<_, _>> =
         Ok((V1(1), 1));
 
-    let Ok((V1(a) | V2(a) | V3(a), ref b)) | Err(Ok((a, ref b)) | Err((a, ref b))): Result<
+    let (Ok((V1(a) | V2(a) | V3(a), ref b)) | Err(Ok((a, ref b)) | Err((a, ref b)))): Result<
         _,
         Result<_, _>,
     > = Ok((V1(1), 1));

src/test/ui/or-patterns/const-fn.rs

@@ -3,28 +3,28 @@
 
 const fn foo((Ok(a) | Err(a)): Result<i32, i32>) {
     let x = Ok(3);
-    let Ok(y) | Err(y) = x;
+    let (Ok(y) | Err(y)) = x;
 }
 
 const X: () = {
     let x = Ok(3);
-    let Ok(y) | Err(y) = x;
+    let (Ok(y) | Err(y)) = x;
 };
 
 static Y: () = {
     let x = Ok(3);
-    let Ok(y) | Err(y) = x;
+    let (Ok(y) | Err(y)) = x;
 };
 
 static mut Z: () = {
     let x = Ok(3);
-    let Ok(y) | Err(y) = x;
+    let (Ok(y) | Err(y)) = x;
 };
 
 fn main() {
     let _: [(); {
         let x = Ok(3);
-        let Ok(y) | Err(y) = x;
+        let (Ok(y) | Err(y)) = x;
         2
     }];
 }

src/test/ui/or-patterns/feature-gate-or_patterns-leading-let.rs

@@ -5,4 +5,5 @@ fn main() {}
 #[cfg(FALSE)]
 fn gated_leading_vert_in_let() {
     let | A; //~ ERROR or-patterns syntax is experimental
+    //~^ ERROR top-level or-patterns are not allowed
 }

src/test/ui/or-patterns/feature-gate-or_patterns-leading-let.stderr

@@ -1,3 +1,9 @@
+error: top-level or-patterns are not allowed in `let` bindings
+  --> $DIR/feature-gate-or_patterns-leading-let.rs:7:9
+   |
+LL |     let | A;
+   |         ^^^ help: remove the `|`: `A`
+
 error[E0658]: or-patterns syntax is experimental
   --> $DIR/feature-gate-or_patterns-leading-let.rs:7:9
    |
@@ -7,6 +13,6 @@ LL |     let | A;
    = note: see issue #54883 <https://github.com/rust-lang/rust/issues/54883> for more information
    = help: add `#![feature(or_patterns)]` to the crate attributes to enable
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0658`.

src/test/ui/or-patterns/feature-gate-or_patterns.rs

@@ -26,7 +26,9 @@ fn or_patterns() {
     // Gated:
 
     let | A | B; //~ ERROR or-patterns syntax is experimental
+    //~^ ERROR top-level or-patterns are not allowed
     let A | B; //~ ERROR or-patterns syntax is experimental
+    //~^ ERROR top-level or-patterns are not allowed
     for | A | B in 0 {} //~ ERROR or-patterns syntax is experimental
     for A | B in 0 {} //~ ERROR or-patterns syntax is experimental
     fn fun((A | B): _) {} //~ ERROR or-patterns syntax is experimental

src/test/ui/or-patterns/feature-gate-or_patterns.stderr

@@ -1,3 +1,15 @@
+error: top-level or-patterns are not allowed in `let` bindings
+  --> $DIR/feature-gate-or_patterns.rs:28:9
+   |
+LL |     let | A | B;
+   |         ^^^^^^^ help: wrap the pattern in parentheses: `(A | B)`
+
+error: top-level or-patterns are not allowed in `let` bindings
+  --> $DIR/feature-gate-or_patterns.rs:30:9
+   |
+LL |     let A | B;
+   |         ^^^^^ help: wrap the pattern in parentheses: `(A | B)`
+
 error[E0658]: or-patterns syntax is experimental
   --> $DIR/feature-gate-or_patterns.rs:5:14
    |
@@ -17,7 +29,7 @@ LL |     let | A | B;
    = help: add `#![feature(or_patterns)]` to the crate attributes to enable
 
 error[E0658]: or-patterns syntax is experimental
-  --> $DIR/feature-gate-or_patterns.rs:29:9
+  --> $DIR/feature-gate-or_patterns.rs:30:9
    |
 LL |     let A | B;
    |         ^^^^^
@@ -26,7 +38,7 @@ LL |     let A | B;
    = help: add `#![feature(or_patterns)]` to the crate attributes to enable
 
 error[E0658]: or-patterns syntax is experimental
-  --> $DIR/feature-gate-or_patterns.rs:30:9
+  --> $DIR/feature-gate-or_patterns.rs:32:9
    |
 LL |     for | A | B in 0 {}
    |         ^^^^^^^
@@ -35,7 +47,7 @@ LL |     for | A | B in 0 {}
    = help: add `#![feature(or_patterns)]` to the crate attributes to enable
 
 error[E0658]: or-patterns syntax is experimental
-  --> $DIR/feature-gate-or_patterns.rs:31:9
+  --> $DIR/feature-gate-or_patterns.rs:33:9
    |
 LL |     for A | B in 0 {}
    |         ^^^^^
@@ -44,7 +56,7 @@ LL |     for A | B in 0 {}
    = help: add `#![feature(or_patterns)]` to the crate attributes to enable
 
 error[E0658]: or-patterns syntax is experimental
-  --> $DIR/feature-gate-or_patterns.rs:32:13
+  --> $DIR/feature-gate-or_patterns.rs:34:13
    |
 LL |     fn fun((A | B): _) {}
    |             ^^^^^
@@ -53,7 +65,7 @@ LL |     fn fun((A | B): _) {}
    = help: add `#![feature(or_patterns)]` to the crate attributes to enable
 
 error[E0658]: or-patterns syntax is experimental
-  --> $DIR/feature-gate-or_patterns.rs:33:15
+  --> $DIR/feature-gate-or_patterns.rs:35:15
    |
 LL |     let _ = |(A | B): u8| ();
    |               ^^^^^
@@ -62,7 +74,7 @@ LL |     let _ = |(A | B): u8| ();
    = help: add `#![feature(or_patterns)]` to the crate attributes to enable
 
 error[E0658]: or-patterns syntax is experimental
-  --> $DIR/feature-gate-or_patterns.rs:34:10
+  --> $DIR/feature-gate-or_patterns.rs:36:10
    |
 LL |     let (A | B);
    |          ^^^^^
@@ -71,7 +83,7 @@ LL |     let (A | B);
    = help: add `#![feature(or_patterns)]` to the crate attributes to enable
 
 error[E0658]: or-patterns syntax is experimental
-  --> $DIR/feature-gate-or_patterns.rs:35:10
+  --> $DIR/feature-gate-or_patterns.rs:37:10
    |
 LL |     let (A | B,);
    |          ^^^^^
@@ -80,7 +92,7 @@ LL |     let (A | B,);
    = help: add `#![feature(or_patterns)]` to the crate attributes to enable
 
 error[E0658]: or-patterns syntax is experimental
-  --> $DIR/feature-gate-or_patterns.rs:36:11
+  --> $DIR/feature-gate-or_patterns.rs:38:11
    |
 LL |     let A(B | C);
    |           ^^^^^
@@ -89,7 +101,7 @@ LL |     let A(B | C);
    = help: add `#![feature(or_patterns)]` to the crate attributes to enable
 
 error[E0658]: or-patterns syntax is experimental
-  --> $DIR/feature-gate-or_patterns.rs:37:14
+  --> $DIR/feature-gate-or_patterns.rs:39:14
    |
 LL |     let E::V(B | C);
    |              ^^^^^
@@ -98,7 +110,7 @@ LL |     let E::V(B | C);
    = help: add `#![feature(or_patterns)]` to the crate attributes to enable
 
 error[E0658]: or-patterns syntax is experimental
-  --> $DIR/feature-gate-or_patterns.rs:38:17
+  --> $DIR/feature-gate-or_patterns.rs:40:17
    |
 LL |     let S { f1: B | C, f2 };
    |                 ^^^^^
@@ -107,7 +119,7 @@ LL |     let S { f1: B | C, f2 };
    = help: add `#![feature(or_patterns)]` to the crate attributes to enable
 
 error[E0658]: or-patterns syntax is experimental
-  --> $DIR/feature-gate-or_patterns.rs:39:20
+  --> $DIR/feature-gate-or_patterns.rs:41:20
    |
 LL |     let E::V { f1: B | C, f2 };
    |                    ^^^^^
@@ -116,7 +128,7 @@ LL |     let E::V { f1: B | C, f2 };
    = help: add `#![feature(or_patterns)]` to the crate attributes to enable
 
 error[E0658]: or-patterns syntax is experimental
-  --> $DIR/feature-gate-or_patterns.rs:40:10
+  --> $DIR/feature-gate-or_patterns.rs:42:10
    |
 LL |     let [A | B];
    |          ^^^^^
@@ -169,6 +181,6 @@ LL | accept_pat!([p | q]);
    = note: see issue #54883 <https://github.com/rust-lang/rust/issues/54883> for more information
    = help: add `#![feature(or_patterns)]` to the crate attributes to enable
 
-error: aborting due to 19 previous errors
+error: aborting due to 21 previous errors
 
 For more information about this error, try `rustc --explain E0658`.

src/test/ui/or-patterns/fn-param-wrap-parens.fixed

@@ -11,4 +11,4 @@ enum E { A, B }
 use E::*;
 
 #[cfg(FALSE)]
-fn fun1((A | B): E) {} //~ ERROR an or-pattern parameter must be wrapped in parentheses
+fn fun1((A | B): E) {} //~ ERROR top-level or-patterns are not allowed

src/test/ui/or-patterns/fn-param-wrap-parens.rs

@@ -11,4 +11,4 @@ enum E { A, B }
 use E::*;
 
 #[cfg(FALSE)]
-fn fun1(A | B: E) {} //~ ERROR an or-pattern parameter must be wrapped in parentheses
+fn fun1(A | B: E) {} //~ ERROR top-level or-patterns are not allowed

src/test/ui/or-patterns/fn-param-wrap-parens.stderr

@@ -1,4 +1,4 @@
-error: an or-pattern parameter must be wrapped in parentheses
+error: top-level or-patterns are not allowed in function parameters
   --> $DIR/fn-param-wrap-parens.rs:14:9
    |
 LL | fn fun1(A | B: E) {}

src/test/ui/or-patterns/inconsistent-modes.rs

@@ -4,23 +4,23 @@
 #![allow(non_camel_case_types)]
 fn main() {
     // One level:
-    let Ok(a) | Err(ref a): Result<&u8, u8> = Ok(&0);
+    let (Ok(a) | Err(ref a)): Result<&u8, u8> = Ok(&0);
     //~^ ERROR variable `a` is bound inconsistently
-    let Ok(ref mut a) | Err(a): Result<u8, &mut u8> = Ok(0);
+    let (Ok(ref mut a) | Err(a)): Result<u8, &mut u8> = Ok(0);
     //~^ ERROR variable `a` is bound inconsistently
-    let Ok(ref a) | Err(ref mut a): Result<&u8, &mut u8> = Ok(&0);
+    let (Ok(ref a) | Err(ref mut a)): Result<&u8, &mut u8> = Ok(&0);
     //~^ ERROR variable `a` is bound inconsistently
     //~| ERROR mismatched types
-    let Ok((ref a, b)) | Err((ref mut a, ref b)) = Ok((0, &0));
+    let (Ok((ref a, b)) | Err((ref mut a, ref b))) = Ok((0, &0));
     //~^ ERROR variable `a` is bound inconsistently
     //~| ERROR variable `b` is bound inconsistently
     //~| ERROR mismatched types
 
     // Two levels:
-    let Ok(Ok(a) | Err(a)) | Err(ref a) = Err(0);
+    let (Ok(Ok(a) | Err(a)) | Err(ref a)) = Err(0);
     //~^ ERROR variable `a` is bound inconsistently
 
     // Three levels:
-    let Ok([Ok((Ok(ref a) | Err(a),)) | Err(a)]) | Err(a) = Err(&1);
+    let (Ok([Ok((Ok(ref a) | Err(a),)) | Err(a)]) | Err(a)) = Err(&1);
     //~^ ERROR variable `a` is bound inconsistently
 }

src/test/ui/or-patterns/inconsistent-modes.stderr

@@ -1,74 +1,74 @@
 error[E0409]: variable `a` is bound inconsistently across alternatives separated by `|`
-  --> $DIR/inconsistent-modes.rs:7:25
+  --> $DIR/inconsistent-modes.rs:7:26
    |
-LL |     let Ok(a) | Err(ref a): Result<&u8, u8> = Ok(&0);
-   |            -            ^ bound in different ways
-   |            |
-   |            first binding
+LL |     let (Ok(a) | Err(ref a)): Result<&u8, u8> = Ok(&0);
+   |             -            ^ bound in different ways
+   |             |
+   |             first binding
 
 error[E0409]: variable `a` is bound inconsistently across alternatives separated by `|`
-  --> $DIR/inconsistent-modes.rs:9:29
+  --> $DIR/inconsistent-modes.rs:9:30
    |
-LL |     let Ok(ref mut a) | Err(a): Result<u8, &mut u8> = Ok(0);
-   |                    -        ^ bound in different ways
-   |                    |
-   |                    first binding
+LL |     let (Ok(ref mut a) | Err(a)): Result<u8, &mut u8> = Ok(0);
+   |                     -        ^ bound in different ways
+   |                     |
+   |                     first binding
 
 error[E0409]: variable `a` is bound inconsistently across alternatives separated by `|`
-  --> $DIR/inconsistent-modes.rs:11:33
+  --> $DIR/inconsistent-modes.rs:11:34
    |
-LL |     let Ok(ref a) | Err(ref mut a): Result<&u8, &mut u8> = Ok(&0);
-   |                - first binding  ^ bound in different ways
+LL |     let (Ok(ref a) | Err(ref mut a)): Result<&u8, &mut u8> = Ok(&0);
+   |                 - first binding  ^ bound in different ways
 
 error[E0409]: variable `a` is bound inconsistently across alternatives separated by `|`
-  --> $DIR/inconsistent-modes.rs:14:39
+  --> $DIR/inconsistent-modes.rs:14:40
    |
-LL |     let Ok((ref a, b)) | Err((ref mut a, ref b)) = Ok((0, &0));
-   |                 - first binding       ^ bound in different ways
+LL |     let (Ok((ref a, b)) | Err((ref mut a, ref b))) = Ok((0, &0));
+   |                  - first binding       ^ bound in different ways
 
 error[E0409]: variable `b` is bound inconsistently across alternatives separated by `|`
-  --> $DIR/inconsistent-modes.rs:14:46
+  --> $DIR/inconsistent-modes.rs:14:47
    |
-LL |     let Ok((ref a, b)) | Err((ref mut a, ref b)) = Ok((0, &0));
-   |                    - first binding           ^ bound in different ways
+LL |     let (Ok((ref a, b)) | Err((ref mut a, ref b))) = Ok((0, &0));
+   |                     - first binding           ^ bound in different ways
 
 error[E0409]: variable `a` is bound inconsistently across alternatives separated by `|`
-  --> $DIR/inconsistent-modes.rs:20:38
+  --> $DIR/inconsistent-modes.rs:20:39
    |
-LL |     let Ok(Ok(a) | Err(a)) | Err(ref a) = Err(0);
-   |                        -             ^ bound in different ways
-   |                        |
-   |                        first binding
+LL |     let (Ok(Ok(a) | Err(a)) | Err(ref a)) = Err(0);
+   |                         -             ^ bound in different ways
+   |                         |
+   |                         first binding
 
 error[E0409]: variable `a` is bound inconsistently across alternatives separated by `|`
-  --> $DIR/inconsistent-modes.rs:24:33
+  --> $DIR/inconsistent-modes.rs:24:34
    |
-LL |     let Ok([Ok((Ok(ref a) | Err(a),)) | Err(a)]) | Err(a) = Err(&1);
-   |                        -        ^ bound in different ways
-   |                        |
-   |                        first binding
+LL |     let (Ok([Ok((Ok(ref a) | Err(a),)) | Err(a)]) | Err(a)) = Err(&1);
+   |                         -        ^ bound in different ways
+   |                         |
+   |                         first binding
 
 error[E0308]: mismatched types
-  --> $DIR/inconsistent-modes.rs:11:25
+  --> $DIR/inconsistent-modes.rs:11:26
    |
-LL |     let Ok(ref a) | Err(ref mut a): Result<&u8, &mut u8> = Ok(&0);
-   |            -----        ^^^^^^^^^   -------------------- expected due to this
-   |            |            |
-   |            |            types differ in mutability
-   |            first introduced with type `&&u8` here
+LL |     let (Ok(ref a) | Err(ref mut a)): Result<&u8, &mut u8> = Ok(&0);
+   |             -----        ^^^^^^^^^    -------------------- expected due to this
+   |             |            |
+   |             |            types differ in mutability
+   |             first introduced with type `&&u8` here
    |
    = note: expected type `&&u8`
               found type `&mut &mut u8`
    = note: a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
-  --> $DIR/inconsistent-modes.rs:14:31
+  --> $DIR/inconsistent-modes.rs:14:32
    |
-LL |     let Ok((ref a, b)) | Err((ref mut a, ref b)) = Ok((0, &0));
-   |             -----             ^^^^^^^^^            ----------- this expression has type `Result<({integer}, &{integer}), (_, _)>`
-   |             |                 |
-   |             |                 types differ in mutability
-   |             first introduced with type `&{integer}` here
+LL |     let (Ok((ref a, b)) | Err((ref mut a, ref b))) = Ok((0, &0));
+   |              -----             ^^^^^^^^^             ----------- this expression has type `Result<({integer}, &{integer}), (_, _)>`
+   |              |                 |
+   |              |                 types differ in mutability
+   |              first introduced with type `&{integer}` here
    |
    = note: expected type `&{integer}`
               found type `&mut _`

src/test/ui/or-patterns/issue-69875-should-have-been-expanded-earlier-non-exhaustive.rs

@@ -1,7 +1,7 @@
 #![feature(or_patterns)]
 
 fn main() {
-    let 0 | (1 | 2) = 0; //~ ERROR refutable pattern in local binding
+    let (0 | (1 | 2)) = 0; //~ ERROR refutable pattern in local binding
     match 0 {
         //~^ ERROR non-exhaustive patterns
         0 | (1 | 2) => {}

src/test/ui/or-patterns/issue-69875-should-have-been-expanded-earlier-non-exhaustive.stderr

@@ -1,16 +1,16 @@
 error[E0005]: refutable pattern in local binding: `i32::MIN..=-1_i32` and `3_i32..=i32::MAX` not covered
-  --> $DIR/issue-69875-should-have-been-expanded-earlier-non-exhaustive.rs:4:9
+  --> $DIR/issue-69875-should-have-been-expanded-earlier-non-exhaustive.rs:4:10
    |
-LL |     let 0 | (1 | 2) = 0;
-   |         ^^^^^^^^^^^ patterns `i32::MIN..=-1_i32` and `3_i32..=i32::MAX` not covered
+LL |     let (0 | (1 | 2)) = 0;
+   |          ^^^^^^^^^^^ patterns `i32::MIN..=-1_i32` and `3_i32..=i32::MAX` not covered
    |
    = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
    = note: the matched value is of type `i32`
 help: you might want to use `if let` to ignore the variant that isn't matched
    |
-LL |     if let 0 | (1 | 2) = 0 { /* */ }
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     if let (0 | (1 | 2)) = 0 { /* */ }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0004]: non-exhaustive patterns: `i32::MIN..=-1_i32` and `3_i32..=i32::MAX` not covered
   --> $DIR/issue-69875-should-have-been-expanded-earlier-non-exhaustive.rs:5:11

src/test/ui/or-patterns/issue-69875-should-have-been-expanded-earlier.rs

@@ -3,7 +3,7 @@
 #![feature(or_patterns)]
 
 fn main() {
-    let 0 | (1 | _) = 0;
+    let (0 | (1 | _)) = 0;
     if let 0 | (1 | 2) = 0 {}
     if let x @ 0 | x @ (1 | 2) = 0 {}
 }

src/test/ui/or-patterns/let-pattern.rs

@@ -3,7 +3,7 @@
 // run-pass
 
 fn or_pat_let(x: Result<u32, u32>) -> u32 {
-    let Ok(y) | Err(y) = x;
+    let (Ok(y) | Err(y)) = x;
     y
 }
 

src/test/ui/or-patterns/mismatched-bindings-async-fn.rs

@@ -8,7 +8,7 @@ async fn a((x | s): String) {}
 //~| ERROR variable `s` is not bound in all patterns
 
 async fn b() {
-    let x | s = String::new();
+    let (x | s) = String::new();
     //~^ ERROR variable `x` is not bound in all patterns
     //~| ERROR variable `s` is not bound in all patterns
 }

src/test/ui/or-patterns/mismatched-bindings-async-fn.stderr

@@ -15,20 +15,20 @@ LL | async fn a((x | s): String) {}
    |             variable not in all patterns
 
 error[E0408]: variable `s` is not bound in all patterns
-  --> $DIR/mismatched-bindings-async-fn.rs:11:9
+  --> $DIR/mismatched-bindings-async-fn.rs:11:10
    |
-LL |     let x | s = String::new();
-   |         ^   - variable not in all patterns
-   |         |
-   |         pattern doesn't bind `s`
+LL |     let (x | s) = String::new();
+   |          ^   - variable not in all patterns
+   |          |
+   |          pattern doesn't bind `s`
 
 error[E0408]: variable `x` is not bound in all patterns
-  --> $DIR/mismatched-bindings-async-fn.rs:11:13
+  --> $DIR/mismatched-bindings-async-fn.rs:11:14
    |
-LL |     let x | s = String::new();
-   |         -   ^ pattern doesn't bind `x`
-   |         |
-   |         variable not in all patterns
+LL |     let (x | s) = String::new();
+   |          -   ^ pattern doesn't bind `x`
+   |          |
+   |          variable not in all patterns
 
 error: aborting due to 4 previous errors
 

src/test/ui/or-patterns/missing-bindings.rs

@@ -17,7 +17,7 @@ fn check_handling_of_paths() {
     }
 
     use bar::foo::{alpha, charlie};
-    let alpha | beta | charlie = alpha; //~  ERROR variable `beta` is not bound in all patterns
+    let (alpha | beta | charlie) = alpha; //~  ERROR variable `beta` is not bound in all patterns
     match Some(alpha) {
         Some(alpha | beta) => {} //~ ERROR variable `beta` is not bound in all patterns
     }
@@ -31,19 +31,19 @@ fn check_misc_nesting() {
 
     // One level:
     const X: E<u8> = B(0);
-    let A(a, _) | _ = X; //~ ERROR variable `a` is not bound in all patterns
-    let _ | B(a) = X; //~ ERROR variable `a` is not bound in all patterns
-    let A(..) | B(a) = X; //~ ERROR variable `a` is not bound in all patterns
-    let A(a, _) | B(_) = X; //~ ERROR variable `a` is not bound in all patterns
-    let A(_, a) | B(_) = X; //~ ERROR variable `a` is not bound in all patterns
-    let A(a, b) | B(a) = X; //~ ERROR variable `b` is not bound in all patterns
+    let (A(a, _) | _) = X; //~ ERROR variable `a` is not bound in all patterns
+    let (_ | B(a)) = X; //~ ERROR variable `a` is not bound in all patterns
+    let (A(..) | B(a)) = X; //~ ERROR variable `a` is not bound in all patterns
+    let (A(a, _) | B(_)) = X; //~ ERROR variable `a` is not bound in all patterns
+    let (A(_, a) | B(_)) = X; //~ ERROR variable `a` is not bound in all patterns
+    let (A(a, b) | B(a)) = X; //~ ERROR variable `b` is not bound in all patterns
 
     // Two levels:
     const Y: E<E<u8>> = B(B(0));
-    let A(A(..) | B(_), _) | B(a) = Y; //~ ERROR variable `a` is not bound in all patterns
-    let A(A(..) | B(a), _) | B(A(a, _) | B(a)) = Y;
+    let (A(A(..) | B(_), _) | B(a)) = Y; //~ ERROR variable `a` is not bound in all patterns
+    let (A(A(..) | B(a), _) | B(A(a, _) | B(a))) = Y;
     //~^ ERROR variable `a` is not bound in all patterns
-    let A(A(a, b) | B(c), d) | B(e) = Y;
+    let (A(A(a, b) | B(c), d) | B(e)) = Y;
     //~^ ERROR variable `a` is not bound in all patterns
     //~| ERROR variable `a` is not bound in all patterns
     //~| ERROR variable `b` is not bound in all patterns

src/test/ui/or-patterns/missing-bindings.stderr

@@ -1,11 +1,11 @@
 error[E0408]: variable `beta` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:20:9
+  --> $DIR/missing-bindings.rs:20:10
    |
-LL |     let alpha | beta | charlie = alpha;
-   |         ^^^^^   ----   ^^^^^^^ pattern doesn't bind `beta`
-   |         |       |
-   |         |       variable not in all patterns
-   |         pattern doesn't bind `beta`
+LL |     let (alpha | beta | charlie) = alpha;
+   |          ^^^^^   ----   ^^^^^^^ pattern doesn't bind `beta`
+   |          |       |
+   |          |       variable not in all patterns
+   |          pattern doesn't bind `beta`
 
 error[E0408]: variable `beta` is not bound in all patterns
   --> $DIR/missing-bindings.rs:22:14
@@ -16,132 +16,132 @@ LL |         Some(alpha | beta) => {}
    |              pattern doesn't bind `beta`
 
 error[E0408]: variable `a` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:34:19
+  --> $DIR/missing-bindings.rs:34:20
    |
-LL |     let A(a, _) | _ = X;
-   |           -       ^ pattern doesn't bind `a`
-   |           |
-   |           variable not in all patterns
+LL |     let (A(a, _) | _) = X;
+   |            -       ^ pattern doesn't bind `a`
+   |            |
+   |            variable not in all patterns
 
 error[E0408]: variable `a` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:35:9
+  --> $DIR/missing-bindings.rs:35:10
    |
-LL |     let _ | B(a) = X;
-   |         ^     - variable not in all patterns
-   |         |
-   |         pattern doesn't bind `a`
+LL |     let (_ | B(a)) = X;
+   |          ^     - variable not in all patterns
+   |          |
+   |          pattern doesn't bind `a`
 
 error[E0408]: variable `a` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:36:9
+  --> $DIR/missing-bindings.rs:36:10
    |
-LL |     let A(..) | B(a) = X;
-   |         ^^^^^     - variable not in all patterns
-   |         |
-   |         pattern doesn't bind `a`
+LL |     let (A(..) | B(a)) = X;
+   |          ^^^^^     - variable not in all patterns
+   |          |
+   |          pattern doesn't bind `a`
 
 error[E0408]: variable `a` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:37:19
+  --> $DIR/missing-bindings.rs:37:20
    |
-LL |     let A(a, _) | B(_) = X;
-   |           -       ^^^^ pattern doesn't bind `a`
-   |           |
-   |           variable not in all patterns
+LL |     let (A(a, _) | B(_)) = X;
+   |            -       ^^^^ pattern doesn't bind `a`
+   |            |
+   |            variable not in all patterns
 
 error[E0408]: variable `a` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:38:19
+  --> $DIR/missing-bindings.rs:38:20
    |
-LL |     let A(_, a) | B(_) = X;
-   |              -    ^^^^ pattern doesn't bind `a`
-   |              |
-   |              variable not in all patterns
+LL |     let (A(_, a) | B(_)) = X;
+   |               -    ^^^^ pattern doesn't bind `a`
+   |               |
+   |               variable not in all patterns
 
 error[E0408]: variable `b` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:39:19
+  --> $DIR/missing-bindings.rs:39:20
    |
-LL |     let A(a, b) | B(a) = X;
-   |              -    ^^^^ pattern doesn't bind `b`
-   |              |
-   |              variable not in all patterns
+LL |     let (A(a, b) | B(a)) = X;
+   |               -    ^^^^ pattern doesn't bind `b`
+   |               |
+   |               variable not in all patterns
 
 error[E0408]: variable `a` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:43:9
+  --> $DIR/missing-bindings.rs:43:10
    |
-LL |     let A(A(..) | B(_), _) | B(a) = Y;
-   |         ^^^^^^^^^^^^^^^^^^     - variable not in all patterns
-   |         |
-   |         pattern doesn't bind `a`
+LL |     let (A(A(..) | B(_), _) | B(a)) = Y;
+   |          ^^^^^^^^^^^^^^^^^^     - variable not in all patterns
+   |          |
+   |          pattern doesn't bind `a`
 
 error[E0408]: variable `a` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:44:11
+  --> $DIR/missing-bindings.rs:44:12
    |
-LL |     let A(A(..) | B(a), _) | B(A(a, _) | B(a)) = Y;
-   |           ^^^^^     - variable not in all patterns
-   |           |
-   |           pattern doesn't bind `a`
+LL |     let (A(A(..) | B(a), _) | B(A(a, _) | B(a))) = Y;
+   |            ^^^^^     - variable not in all patterns
+   |            |
+   |            pattern doesn't bind `a`
 
 error[E0408]: variable `a` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:46:21
+  --> $DIR/missing-bindings.rs:46:22
    |
-LL |     let A(A(a, b) | B(c), d) | B(e) = Y;
-   |             -       ^^^^ pattern doesn't bind `a`
-   |             |
-   |             variable not in all patterns
+LL |     let (A(A(a, b) | B(c), d) | B(e)) = Y;
+   |              -       ^^^^ pattern doesn't bind `a`
+   |              |
+   |              variable not in all patterns
 
 error[E0408]: variable `b` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:46:21
+  --> $DIR/missing-bindings.rs:46:22
    |
-LL |     let A(A(a, b) | B(c), d) | B(e) = Y;
-   |                -    ^^^^ pattern doesn't bind `b`
-   |                |
-   |                variable not in all patterns
+LL |     let (A(A(a, b) | B(c), d) | B(e)) = Y;
+   |                 -    ^^^^ pattern doesn't bind `b`
+   |                 |
+   |                 variable not in all patterns
 
 error[E0408]: variable `c` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:46:11
+  --> $DIR/missing-bindings.rs:46:12
    |
-LL |     let A(A(a, b) | B(c), d) | B(e) = Y;
-   |           ^^^^^^^     - variable not in all patterns
-   |           |
-   |           pattern doesn't bind `c`
+LL |     let (A(A(a, b) | B(c), d) | B(e)) = Y;
+   |            ^^^^^^^     - variable not in all patterns
+   |            |
+   |            pattern doesn't bind `c`
 
 error[E0408]: variable `a` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:46:32
+  --> $DIR/missing-bindings.rs:46:33
    |
-LL |     let A(A(a, b) | B(c), d) | B(e) = Y;
-   |             -                  ^^^^ pattern doesn't bind `a`
-   |             |
-   |             variable not in all patterns
+LL |     let (A(A(a, b) | B(c), d) | B(e)) = Y;
+   |              -                  ^^^^ pattern doesn't bind `a`
+   |              |
+   |              variable not in all patterns
 
 error[E0408]: variable `b` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:46:32
+  --> $DIR/missing-bindings.rs:46:33
    |
-LL |     let A(A(a, b) | B(c), d) | B(e) = Y;
-   |                -               ^^^^ pattern doesn't bind `b`
-   |                |
-   |                variable not in all patterns
+LL |     let (A(A(a, b) | B(c), d) | B(e)) = Y;
+   |                 -               ^^^^ pattern doesn't bind `b`
+   |                 |
+   |                 variable not in all patterns
 
 error[E0408]: variable `c` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:46:32
+  --> $DIR/missing-bindings.rs:46:33
    |
-LL |     let A(A(a, b) | B(c), d) | B(e) = Y;
-   |                       -        ^^^^ pattern doesn't bind `c`
-   |                       |
-   |                       variable not in all patterns
+LL |     let (A(A(a, b) | B(c), d) | B(e)) = Y;
+   |                        -        ^^^^ pattern doesn't bind `c`
+   |                        |
+   |                        variable not in all patterns
 
 error[E0408]: variable `d` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:46:32
+  --> $DIR/missing-bindings.rs:46:33
    |
-LL |     let A(A(a, b) | B(c), d) | B(e) = Y;
-   |                           -    ^^^^ pattern doesn't bind `d`
-   |                           |
-   |                           variable not in all patterns
+LL |     let (A(A(a, b) | B(c), d) | B(e)) = Y;
+   |                            -    ^^^^ pattern doesn't bind `d`
+   |                            |
+   |                            variable not in all patterns
 
 error[E0408]: variable `e` is not bound in all patterns
-  --> $DIR/missing-bindings.rs:46:9
+  --> $DIR/missing-bindings.rs:46:10
    |
-LL |     let A(A(a, b) | B(c), d) | B(e) = Y;
-   |         ^^^^^^^^^^^^^^^^^^^^     - variable not in all patterns
-   |         |
-   |         pattern doesn't bind `e`
+LL |     let (A(A(a, b) | B(c), d) | B(e)) = Y;
+   |          ^^^^^^^^^^^^^^^^^^^^     - variable not in all patterns
+   |          |
+   |          pattern doesn't bind `e`
 
 error[E0408]: variable `a` is not bound in all patterns
   --> $DIR/missing-bindings.rs:62:29

src/test/ui/or-patterns/nested-undelimited-precedence.rs

@@ -0,0 +1,46 @@
+// This test tests the precedence of `|` (or-patterns) undelimited nested patterns. In particular,
+// we want to reserve the syntactic space of a pattern followed by a type annotation for possible
+// future type ascription, so we need to make sure that any time a pattern is followed by type
+// annotation (for now), the pattern is not a top-level or-pattern. However, there are also a few
+// types of patterns that allow undelimited subpatterns that could cause the same ambiguity.
+// Currently, those should be impossible due to precedence rule. This test enforces that.
+
+#![feature(or_patterns)]
+
+enum E {
+    A,
+    B,
+}
+
+fn foo() {
+    use E::*;
+
+    // ok
+    let b @ (A | B): E = A;
+
+    let b @ A | B: E = A; //~ERROR `b` is not bound in all patterns
+    //~^ ERROR top-level or-patterns are not allowed
+}
+
+enum F {
+    A(usize),
+    B(usize),
+}
+
+fn bar() {
+    use F::*;
+
+    // ok
+    let (A(x) | B(x)): F = A(3);
+
+    let &A(_) | B(_): F = A(3); //~ERROR mismatched types
+    //~^ ERROR top-level or-patterns are not allowed
+    let &&A(_) | B(_): F = A(3); //~ERROR mismatched types
+    //~^ ERROR top-level or-patterns are not allowed
+    let &mut A(_) | B(_): F = A(3); //~ERROR mismatched types
+    //~^ ERROR top-level or-patterns are not allowed
+    let &&mut A(_) | B(_): F = A(3); //~ERROR mismatched types
+    //~^ ERROR top-level or-patterns are not allowed
+}
+
+fn main() {}

src/test/ui/or-patterns/nested-undelimited-precedence.stderr

@@ -0,0 +1,86 @@
+error: top-level or-patterns are not allowed in `let` bindings
+  --> $DIR/nested-undelimited-precedence.rs:21:9
+   |
+LL |     let b @ A | B: E = A;
+   |         ^^^^^^^^^ help: wrap the pattern in parentheses: `(b @ A | B)`
+
+error: top-level or-patterns are not allowed in `let` bindings
+  --> $DIR/nested-undelimited-precedence.rs:36:9
+   |
+LL |     let &A(_) | B(_): F = A(3);
+   |         ^^^^^^^^^^^^ help: wrap the pattern in parentheses: `(&A(_) | B(_))`
+
+error: top-level or-patterns are not allowed in `let` bindings
+  --> $DIR/nested-undelimited-precedence.rs:38:9
+   |
+LL |     let &&A(_) | B(_): F = A(3);
+   |         ^^^^^^^^^^^^^ help: wrap the pattern in parentheses: `(&&A(_) | B(_))`
+
+error: top-level or-patterns are not allowed in `let` bindings
+  --> $DIR/nested-undelimited-precedence.rs:40:9
+   |
+LL |     let &mut A(_) | B(_): F = A(3);
+   |         ^^^^^^^^^^^^^^^^ help: wrap the pattern in parentheses: `(&mut A(_) | B(_))`
+
+error: top-level or-patterns are not allowed in `let` bindings
+  --> $DIR/nested-undelimited-precedence.rs:42:9
+   |
+LL |     let &&mut A(_) | B(_): F = A(3);
+   |         ^^^^^^^^^^^^^^^^^ help: wrap the pattern in parentheses: `(&&mut A(_) | B(_))`
+
+error[E0408]: variable `b` is not bound in all patterns
+  --> $DIR/nested-undelimited-precedence.rs:21:17
+   |
+LL |     let b @ A | B: E = A;
+   |         -       ^ pattern doesn't bind `b`
+   |         |
+   |         variable not in all patterns
+
+error[E0308]: mismatched types
+  --> $DIR/nested-undelimited-precedence.rs:36:9
+   |
+LL |     let &A(_) | B(_): F = A(3);
+   |         ^^^^^         - expected due to this
+   |         |
+   |         expected enum `F`, found reference
+   |
+   = note:   expected enum `F`
+           found reference `&_`
+
+error[E0308]: mismatched types
+  --> $DIR/nested-undelimited-precedence.rs:38:9
+   |
+LL |     let &&A(_) | B(_): F = A(3);
+   |         ^^^^^^         - expected due to this
+   |         |
+   |         expected enum `F`, found reference
+   |
+   = note:   expected enum `F`
+           found reference `&_`
+
+error[E0308]: mismatched types
+  --> $DIR/nested-undelimited-precedence.rs:40:9
+   |
+LL |     let &mut A(_) | B(_): F = A(3);
+   |         ^^^^^^^^^         - expected due to this
+   |         |
+   |         expected enum `F`, found `&mut _`
+   |
+   = note:           expected enum `F`
+           found mutable reference `&mut _`
+
+error[E0308]: mismatched types
+  --> $DIR/nested-undelimited-precedence.rs:42:9
+   |
+LL |     let &&mut A(_) | B(_): F = A(3);
+   |         ^^^^^^^^^^         - expected due to this
+   |         |
+   |         expected enum `F`, found reference
+   |
+   = note:   expected enum `F`
+           found reference `&_`
+
+error: aborting due to 10 previous errors
+
+Some errors have detailed explanations: E0308, E0408.
+For more information about an error, try `rustc --explain E0308`.

src/test/ui/or-patterns/or-patterns-binding-type-mismatch.rs

@@ -52,10 +52,10 @@ fn main() {
     = Some((0u8, Some((1u16, 2u32))))
     {}
 
-    let Blah::A(_, x, y) | Blah::B(x, y) = Blah::A(1, 1, 2);
+    let (Blah::A(_, x, y) | Blah::B(x, y)) = Blah::A(1, 1, 2);
     //~^ ERROR mismatched types
 
-    let (x, y) | (y, x) = (0u8, 1u16);
+    let ((x, y) | (y, x)) = (0u8, 1u16);
     //~^ ERROR mismatched types
     //~| ERROR mismatched types
 

src/test/ui/or-patterns/or-patterns-binding-type-mismatch.stderr

@@ -187,35 +187,35 @@ LL |     = Some((0u8, Some((1u16, 2u32))))
    = note: a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
-  --> $DIR/or-patterns-binding-type-mismatch.rs:55:39
+  --> $DIR/or-patterns-binding-type-mismatch.rs:55:40
    |
-LL |     let Blah::A(_, x, y) | Blah::B(x, y) = Blah::A(1, 1, 2);
-   |                       -               ^    ---------------- this expression has type `Blah`
-   |                       |               |
-   |                       |               expected `usize`, found `isize`
-   |                       first introduced with type `usize` here
+LL |     let (Blah::A(_, x, y) | Blah::B(x, y)) = Blah::A(1, 1, 2);
+   |                        -               ^     ---------------- this expression has type `Blah`
+   |                        |               |
+   |                        |               expected `usize`, found `isize`
+   |                        first introduced with type `usize` here
    |
    = note: a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
-  --> $DIR/or-patterns-binding-type-mismatch.rs:58:19
+  --> $DIR/or-patterns-binding-type-mismatch.rs:58:20
    |
-LL |     let (x, y) | (y, x) = (0u8, 1u16);
-   |             -     ^       ----------- this expression has type `(u8, u16)`
-   |             |     |
-   |             |     expected `u16`, found `u8`
-   |             first introduced with type `u16` here
+LL |     let ((x, y) | (y, x)) = (0u8, 1u16);
+   |              -     ^        ----------- this expression has type `(u8, u16)`
+   |              |     |
+   |              |     expected `u16`, found `u8`
+   |              first introduced with type `u16` here
    |
    = note: a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
-  --> $DIR/or-patterns-binding-type-mismatch.rs:58:22
+  --> $DIR/or-patterns-binding-type-mismatch.rs:58:23
    |
-LL |     let (x, y) | (y, x) = (0u8, 1u16);
-   |          -           ^    ----------- this expression has type `(u8, u16)`
-   |          |           |
-   |          |           expected `u8`, found `u16`
-   |          first introduced with type `u8` here
+LL |     let ((x, y) | (y, x)) = (0u8, 1u16);
+   |           -           ^     ----------- this expression has type `(u8, u16)`
+   |           |           |
+   |           |           expected `u8`, found `u16`
+   |           first introduced with type `u8` here
    |
    = note: a binding must have the same type in all alternatives
 

src/test/ui/or-patterns/or-patterns-default-binding-modes.rs

@@ -37,11 +37,11 @@ fn main() {
     if let &(Ok(x) | Err(x)) = res {
         drop::<u8>(x);
     }
-    let Ok(mut x) | &Err(mut x) = res;
+    let (Ok(mut x) | &Err(mut x)) = res;
     drop::<u8>(x);
     let &(Ok(x) | Err(x)) = res;
     drop::<u8>(x);
-    let Ok(x) | Err(x) = res;
+    let (Ok(x) | Err(x)) = res;
     drop::<&u8>(x);
     for Ok(mut x) | &Err(mut x) in std::iter::once(res) {
         drop::<u8>(x);
@@ -119,9 +119,9 @@ fn main() {
     }
 
     let tri = &Tri::A(&Ok(0));
-    let Tri::A(Ok(mut x) | Err(mut x))
+    let (Tri::A(Ok(mut x) | Err(mut x))
     | Tri::B(&Ok(mut x) | Err(mut x))
-    | &Tri::C(Ok(mut x) | Err(mut x)) = tri;
+    | &Tri::C(Ok(mut x) | Err(mut x))) = tri;
     drop::<u8>(x);
 
     match tri {

src/test/ui/or-patterns/or-patterns-syntactic-fail.rs

@@ -14,8 +14,19 @@ fn no_top_level_or_patterns() {
     //           -------- This looks like an or-pattern but is in fact `|A| (B: E | ())`.
 
     // ...and for now neither do we allow or-patterns at the top level of functions.
-    fn fun1(A | B: E) {} //~ ERROR an or-pattern parameter must be wrapped in parentheses
+    fn fun1(A | B: E) {}
+    //~^ ERROR top-level or-patterns are not allowed
 
     fn fun2(| A | B: E) {}
-    //~^ ERROR an or-pattern parameter must be wrapped in parentheses
+    //~^ ERROR top-level or-patterns are not allowed
+
+    // We don't allow top-level or-patterns before type annotation in let-statements because we
+    // want to reserve this syntactic space for possible future type ascription.
+    let A | B: E = A;
+    //~^ ERROR top-level or-patterns are not allowed
+
+    let | A | B: E = A;
+    //~^ ERROR top-level or-patterns are not allowed
+
+    let (A | B): E = A; // ok -- wrapped in parens
 }

src/test/ui/or-patterns/or-patterns-syntactic-fail.stderr

@@ -1,15 +1,27 @@
-error: an or-pattern parameter must be wrapped in parentheses
+error: top-level or-patterns are not allowed in function parameters
   --> $DIR/or-patterns-syntactic-fail.rs:17:13
    |
 LL |     fn fun1(A | B: E) {}
    |             ^^^^^ help: wrap the pattern in parentheses: `(A | B)`
 
-error: an or-pattern parameter must be wrapped in parentheses
-  --> $DIR/or-patterns-syntactic-fail.rs:19:13
+error: top-level or-patterns are not allowed in function parameters
+  --> $DIR/or-patterns-syntactic-fail.rs:20:13
    |
 LL |     fn fun2(| A | B: E) {}
    |             ^^^^^^^ help: wrap the pattern in parentheses: `(A | B)`
 
+error: top-level or-patterns are not allowed in `let` bindings
+  --> $DIR/or-patterns-syntactic-fail.rs:25:9
+   |
+LL |     let A | B: E = A;
+   |         ^^^^^ help: wrap the pattern in parentheses: `(A | B)`
+
+error: top-level or-patterns are not allowed in `let` bindings
+  --> $DIR/or-patterns-syntactic-fail.rs:28:9
+   |
+LL |     let | A | B: E = A;
+   |         ^^^^^^^ help: wrap the pattern in parentheses: `(A | B)`
+
 error[E0369]: no implementation for `E | ()`
   --> $DIR/or-patterns-syntactic-fail.rs:13:22
    |
@@ -20,6 +32,6 @@ LL |     let _ = |A | B: E| ();
    |
    = note: an implementation of `std::ops::BitOr` might be missing for `E`
 
-error: aborting due to 3 previous errors
+error: aborting due to 5 previous errors
 
 For more information about this error, try `rustc --explain E0369`.

src/test/ui/or-patterns/or-patterns-syntactic-pass.rs

@@ -23,11 +23,11 @@ accept_pat!([p | q]);
 #[cfg(FALSE)]
 fn or_patterns() {
     // Top level of `let`:
-    let | A | B;
-    let A | B;
-    let A | B: u8;
-    let A | B = 0;
-    let A | B: u8 = 0;
+    let (| A | B);
+    let (A | B);
+    let (A | B): u8;
+    let (A | B) = 0;
+    let (A | B): u8 = 0;
 
     // Top level of `for`:
     for | A | B in 0 {}
@@ -69,10 +69,10 @@ fn or_patterns() {
     let [A | B, .. | ..];
 
     // These bind as `(prefix p) | q` as opposed to `prefix (p | q)`:
-    let box 0 | 1; // Unstable; we *can* the precedence if we want.
-    let &0 | 1;
-    let &mut 0 | 1;
-    let x @ 0 | 1;
-    let ref x @ 0 | 1;
-    let ref mut x @ 0 | 1;
+    let (box 0 | 1); // Unstable; we *can* change the precedence if we want.
+    let (&0 | 1);
+    let (&mut 0 | 1);
+    let (x @ 0 | 1);
+    let (ref x @ 0 | 1);
+    let (ref mut x @ 0 | 1);
 }

src/test/ui/or-patterns/remove-leading-vert.fixed

@@ -9,7 +9,7 @@ fn main() {}
 
 #[cfg(FALSE)]
 fn leading() {
-    fn fun1( A: E) {} //~ ERROR an or-pattern parameter must be wrapped in parentheses
+    fn fun1( A: E) {} //~ ERROR top-level or-patterns are not allowed
     fn fun2(  A: E) {} //~ ERROR unexpected `||` before function parameter
     let ( | A): E;
     let ( | A): (E); //~ ERROR unexpected token `||` in pattern
@@ -40,6 +40,9 @@ fn trailing() {
         //~^ ERROR a trailing `|` is not allowed in an or-pattern
     }
 
+    // These test trailing-vert in `let` bindings, but they also test that we don't emit a
+    // duplicate suggestion that would confuse rustfix.
+
     let a  : u8 = 0; //~ ERROR a trailing `|` is not allowed in an or-pattern
     let a  = 0; //~ ERROR a trailing `|` is not allowed in an or-pattern
     let a  ; //~ ERROR a trailing `|` is not allowed in an or-pattern

src/test/ui/or-patterns/remove-leading-vert.rs

@@ -9,7 +9,7 @@ fn main() {}
 
 #[cfg(FALSE)]
 fn leading() {
-    fn fun1( | A: E) {} //~ ERROR an or-pattern parameter must be wrapped in parentheses
+    fn fun1( | A: E) {} //~ ERROR top-level or-patterns are not allowed
     fn fun2( || A: E) {} //~ ERROR unexpected `||` before function parameter
     let ( | A): E;
     let ( || A): (E); //~ ERROR unexpected token `||` in pattern
@@ -40,6 +40,9 @@ fn trailing() {
         //~^ ERROR a trailing `|` is not allowed in an or-pattern
     }
 
+    // These test trailing-vert in `let` bindings, but they also test that we don't emit a
+    // duplicate suggestion that would confuse rustfix.
+
     let a | : u8 = 0; //~ ERROR a trailing `|` is not allowed in an or-pattern
     let a | = 0; //~ ERROR a trailing `|` is not allowed in an or-pattern
     let a | ; //~ ERROR a trailing `|` is not allowed in an or-pattern

src/test/ui/or-patterns/remove-leading-vert.stderr

@@ -1,8 +1,8 @@
-error: an or-pattern parameter must be wrapped in parentheses
+error: top-level or-patterns are not allowed in function parameters
   --> $DIR/remove-leading-vert.rs:12:14
    |
 LL |     fn fun1( | A: E) {}
-   |              ^^^ help: remove the leading `|`: `A`
+   |              ^^^ help: remove the `|`: `A`
 
 error: unexpected `||` before function parameter
   --> $DIR/remove-leading-vert.rs:13:14
@@ -135,23 +135,23 @@ LL |         | A | B | => {}
    |         while parsing this or-pattern starting here
 
 error: a trailing `|` is not allowed in an or-pattern
-  --> $DIR/remove-leading-vert.rs:43:11
+  --> $DIR/remove-leading-vert.rs:46:11
    |
 LL |     let a | : u8 = 0;
    |         - ^ help: remove the `|`
    |         |
    |         while parsing this or-pattern starting here
 
 error: a trailing `|` is not allowed in an or-pattern
-  --> $DIR/remove-leading-vert.rs:44:11
+  --> $DIR/remove-leading-vert.rs:47:11
    |
 LL |     let a | = 0;
    |         - ^ help: remove the `|`
    |         |
    |         while parsing this or-pattern starting here
 
 error: a trailing `|` is not allowed in an or-pattern
-  --> $DIR/remove-leading-vert.rs:45:11
+  --> $DIR/remove-leading-vert.rs:48:11
    |
 LL |     let a | ;
    |         - ^ help: remove the `|`

src/tools/clippy/clippy_lints/src/loops.rs

@@ -885,7 +885,9 @@ struct MinifyingSugg<'a>(Sugg<'a>);
 
 impl<'a> MinifyingSugg<'a> {
     fn as_str(&self) -> &str {
-        let Sugg::NonParen(s) | Sugg::MaybeParen(s) | Sugg::BinOp(_, s) = &self.0;
+        let s = match &self.0 {
+            Sugg::NonParen(s) | Sugg::MaybeParen(s) | Sugg::BinOp(_, s) => s,
+        };
         s.as_ref()
     }