From a7e32a5319f82c19f7c8024efd3afcc1825fa5e2 Mon Sep 17 00:00:00 2001 From: Esteban Küber Date: Sun, 31 Aug 2025 00:42:58 +0000 Subject: Provide suggestion when encountering `match () { () => 1 } + match () { () => 1 }` ``` error[E0308]: mismatched types --> $DIR/expr-as-stmt.rs:69:5 | LL | match () { () => 1 } + match () { () => 1 } | ^^^^^^^^^^^^^^^^^^^^ expected `()`, found integer | help: consider using a semicolon here | LL | match () { () => 1 }; + match () { () => 1 } | + help: alternatively, parentheses are required to parse this as an expression | LL | (match () { () => 1 }) + match () { () => 1 } | + + ``` Parentheses are needed for the `match` to be unambiguously parsed as an expression and not a statement when chaining with binops that are also unops. --- compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs | 11 +++++++++++ tests/ui/parser/expr-as-stmt.stderr | 13 ++++++++++--- tests/ui/suggestions/match-needing-semi.stderr | 17 ++++++++++++++--- 3 files changed, 35 insertions(+), 6 deletions(-) diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs index 5aec50c8b53..e70e444a53d 100644 --- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs +++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs @@ -1914,6 +1914,17 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { self.check_expr_has_type_or_error(expr, self.tcx.types.unit, |err| { if expr.can_have_side_effects() { self.suggest_semicolon_at_end(expr.span, err); + if let hir::ExprKind::Match(..) = expr.kind { + err.multipart_suggestion( + "alternatively, parentheses are required to parse this as an \ + expression", + vec![ + (expr.span.shrink_to_lo(), "(".to_string()), + (expr.span.shrink_to_hi(), ")".to_string()), + ], + Applicability::MaybeIncorrect, + ); + } } }); } diff --git a/tests/ui/parser/expr-as-stmt.stderr b/tests/ui/parser/expr-as-stmt.stderr index 577c3455a71..562162ef394 100644 --- a/tests/ui/parser/expr-as-stmt.stderr +++ b/tests/ui/parser/expr-as-stmt.stderr @@ -227,9 +227,16 @@ error[E0308]: mismatched types --> $DIR/expr-as-stmt.rs:69:5 | LL | match () { () => 1 } + match () { () => 1 } - | ^^^^^^^^^^^^^^^^^^^^- help: consider using a semicolon here - | | - | expected `()`, found integer + | ^^^^^^^^^^^^^^^^^^^^ expected `()`, found integer + | +help: consider using a semicolon here + | +LL | match () { () => 1 }; + match () { () => 1 } + | + +help: alternatively, parentheses are required to parse this as an expression + | +LL | (match () { () => 1 }) + match () { () => 1 } + | + + error[E0308]: mismatched types --> $DIR/expr-as-stmt.rs:75:14 diff --git a/tests/ui/suggestions/match-needing-semi.stderr b/tests/ui/suggestions/match-needing-semi.stderr index b5f01d7038c..8f74997fdbe 100644 --- a/tests/ui/suggestions/match-needing-semi.stderr +++ b/tests/ui/suggestions/match-needing-semi.stderr @@ -28,9 +28,20 @@ LL | | 4 => 1, LL | | 3 => 2, LL | | _ => 2 LL | | } - | | ^- help: consider using a semicolon here - | |_____| - | expected `()`, found integer + | |_____^ expected `()`, found integer + | +help: consider using a semicolon here + | +LL | }; + | + +help: alternatively, parentheses are required to parse this as an expression + | +LL ~ (match 3 { +LL | 4 => 1, +LL | 3 => 2, +LL | _ => 2 +LL ~ }) + | error: aborting due to 2 previous errors -- cgit 1.4.1-3-g733a5