diff options
| -rw-r--r-- | compiler/rustc_ast/src/ast.rs | 16 | ||||
| -rw-r--r-- | compiler/rustc_hir/src/hir.rs | 14 | ||||
| -rw-r--r-- | compiler/rustc_resolve/src/late/diagnostics.rs | 22 | ||||
| -rw-r--r-- | compiler/rustc_typeck/src/check/expr.rs | 5 | ||||
| -rw-r--r-- | src/test/ui/expr/if/bad-if-let-suggestion.rs | 24 | ||||
| -rw-r--r-- | src/test/ui/expr/if/bad-if-let-suggestion.stderr | 69 |
6 files changed, 142 insertions, 8 deletions
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs index f2643d61fc8..e5b61d7000a 100644 --- a/compiler/rustc_ast/src/ast.rs +++ b/compiler/rustc_ast/src/ast.rs @@ -1278,6 +1278,22 @@ impl Expr { }, ) } + + // To a first-order approximation, is this a pattern + pub fn is_approximately_pattern(&self) -> bool { + match &self.peel_parens().kind { + ExprKind::Box(_) + | ExprKind::Array(_) + | ExprKind::Call(_, _) + | ExprKind::Tup(_) + | ExprKind::Lit(_) + | ExprKind::Range(_, _, _) + | ExprKind::Underscore + | ExprKind::Path(_, _) + | ExprKind::Struct(_) => true, + _ => false, + } + } } /// Limit types of a range (inclusive or exclusive) diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs index 9c314f67651..2f5f271dc50 100644 --- a/compiler/rustc_hir/src/hir.rs +++ b/compiler/rustc_hir/src/hir.rs @@ -1813,6 +1813,20 @@ impl Expr<'_> { | ExprKind::Err => true, } } + + // To a first-order approximation, is this a pattern + pub fn is_approximately_pattern(&self) -> bool { + match &self.kind { + ExprKind::Box(_) + | ExprKind::Array(_) + | ExprKind::Call(..) + | ExprKind::Tup(_) + | ExprKind::Lit(_) + | ExprKind::Path(_) + | ExprKind::Struct(..) => true, + _ => false, + } + } } /// Checks if the specified expression is a built-in range literal. diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs index cb39eb5416b..5e52e9b40f0 100644 --- a/compiler/rustc_resolve/src/late/diagnostics.rs +++ b/compiler/rustc_resolve/src/late/diagnostics.rs @@ -265,13 +265,21 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> { ); } match (source, self.diagnostic_metadata.in_if_condition) { - (PathSource::Expr(_), Some(Expr { span, kind: ExprKind::Assign(..), .. })) => { - err.span_suggestion_verbose( - span.shrink_to_lo(), - "you might have meant to use pattern matching", - "let ".to_string(), - Applicability::MaybeIncorrect, - ); + ( + PathSource::Expr(_), + Some(Expr { span: expr_span, kind: ExprKind::Assign(lhs, _, _), .. }), + ) => { + // Icky heuristic so we don't suggest: + // `if (i + 2) = 2` => `if let (i + 2) = 2` (approximately pattern) + // `if 2 = i` => `if let 2 = i` (lhs needs to contain error span) + if lhs.is_approximately_pattern() && lhs.span.contains(span) { + err.span_suggestion_verbose( + expr_span.shrink_to_lo(), + "you might have meant to use pattern matching", + "let ".to_string(), + Applicability::MaybeIncorrect, + ); + } } _ => {} } diff --git a/compiler/rustc_typeck/src/check/expr.rs b/compiler/rustc_typeck/src/check/expr.rs index e3e0063c4ec..9f82bb67bd0 100644 --- a/compiler/rustc_typeck/src/check/expr.rs +++ b/compiler/rustc_typeck/src/check/expr.rs @@ -1035,7 +1035,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { } else { (Applicability::MaybeIncorrect, false) }; - if !lhs.is_syntactic_place_expr() && !matches!(lhs.kind, hir::ExprKind::Lit(_)) { + if !lhs.is_syntactic_place_expr() + && lhs.is_approximately_pattern() + && !matches!(lhs.kind, hir::ExprKind::Lit(_)) + { // Do not suggest `if let x = y` as `==` is way more likely to be the intention. let hir = self.tcx.hir(); if let hir::Node::Expr(hir::Expr { kind: ExprKind::If { .. }, .. }) = diff --git a/src/test/ui/expr/if/bad-if-let-suggestion.rs b/src/test/ui/expr/if/bad-if-let-suggestion.rs new file mode 100644 index 00000000000..a8b2a283039 --- /dev/null +++ b/src/test/ui/expr/if/bad-if-let-suggestion.rs @@ -0,0 +1,24 @@ +// FIXME(compiler-errors): This really should suggest `let` on the RHS of the +// `&&` operator, but that's kinda hard to do because of precedence. +// Instead, for now we just make sure not to suggest `if let let`. +fn a() { + if let x = 1 && i = 2 {} + //~^ ERROR cannot find value `i` in this scope + //~| ERROR `let` expressions in this position are unstable + //~| ERROR mismatched types + //~| ERROR `let` expressions are not supported here +} + +fn b() { + if (i + j) = i {} + //~^ ERROR cannot find value `i` in this scope + //~| ERROR cannot find value `i` in this scope + //~| ERROR cannot find value `j` in this scope +} + +fn c() { + if x[0] = 1 {} + //~^ ERROR cannot find value `x` in this scope +} + +fn main() {} diff --git a/src/test/ui/expr/if/bad-if-let-suggestion.stderr b/src/test/ui/expr/if/bad-if-let-suggestion.stderr new file mode 100644 index 00000000000..60d286fedf5 --- /dev/null +++ b/src/test/ui/expr/if/bad-if-let-suggestion.stderr @@ -0,0 +1,69 @@ +error: `let` expressions are not supported here + --> $DIR/bad-if-let-suggestion.rs:5:8 + | +LL | if let x = 1 && i = 2 {} + | ^^^^^^^^^ + | + = note: only supported directly in conditions of `if` and `while` expressions + +error[E0425]: cannot find value `i` in this scope + --> $DIR/bad-if-let-suggestion.rs:5:21 + | +LL | if let x = 1 && i = 2 {} + | ^ not found in this scope + +error[E0425]: cannot find value `i` in this scope + --> $DIR/bad-if-let-suggestion.rs:13:9 + | +LL | fn a() { + | ------ similarly named function `a` defined here +... +LL | if (i + j) = i {} + | ^ help: a function with a similar name exists: `a` + +error[E0425]: cannot find value `j` in this scope + --> $DIR/bad-if-let-suggestion.rs:13:13 + | +LL | fn a() { + | ------ similarly named function `a` defined here +... +LL | if (i + j) = i {} + | ^ help: a function with a similar name exists: `a` + +error[E0425]: cannot find value `i` in this scope + --> $DIR/bad-if-let-suggestion.rs:13:18 + | +LL | fn a() { + | ------ similarly named function `a` defined here +... +LL | if (i + j) = i {} + | ^ help: a function with a similar name exists: `a` + +error[E0425]: cannot find value `x` in this scope + --> $DIR/bad-if-let-suggestion.rs:20:8 + | +LL | fn a() { + | ------ similarly named function `a` defined here +... +LL | if x[0] = 1 {} + | ^ help: a function with a similar name exists: `a` + +error[E0658]: `let` expressions in this position are unstable + --> $DIR/bad-if-let-suggestion.rs:5:8 + | +LL | if let x = 1 && i = 2 {} + | ^^^^^^^^^ + | + = 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[E0308]: mismatched types + --> $DIR/bad-if-let-suggestion.rs:5:8 + | +LL | if let x = 1 && i = 2 {} + | ^^^^^^^^^^^^^^^^^^ expected `bool`, found `()` + +error: aborting due to 8 previous errors + +Some errors have detailed explanations: E0308, E0425, E0658. +For more information about an error, try `rustc --explain E0308`. |