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Add suggestions for expressions in let patterns
1 parent ae8f558 commit 5e2c8eb

12 files changed

+101
-16
lines changed

‎compiler/rustc_parse/messages.ftl

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -788,6 +788,10 @@ parse_unexpected_expr_in_pat_create_guard_sugg = check the value in an arm guard
788788
789789
parse_unexpected_expr_in_pat_inline_const_sugg = wrap the expression in a inline const (requires `{"#"}![feature(inline_const_pat)]`)
790790
791+
parse_unexpected_expr_in_pat_remove_let_sugg = remove this `let`
792+
793+
parse_unexpected_expr_in_pat_replace_let_else_with_if_sugg = use an `if`
794+
791795
parse_unexpected_expr_in_pat_update_guard_sugg = check the value in the arm guard
792796
793797
parse_unexpected_if_with_if = unexpected `if` in the condition expression

‎compiler/rustc_parse/src/errors.rs

Lines changed: 22 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2492,6 +2492,28 @@ pub(crate) struct UnexpectedExpressionInPatternInlineConstSugg {
24922492
pub end_span: Span,
24932493
}
24942494

2495+
#[derive(Subdiagnostic)]
2496+
#[multipart_suggestion(
2497+
parse_unexpected_expr_in_pat_remove_let_sugg,
2498+
applicability = "maybe-incorrect"
2499+
)]
2500+
pub(crate) struct UnexpectedExpressionInPatternRemoveLetSugg {
2501+
#[suggestion_part(code = "")]
2502+
pub span: Span,
2503+
}
2504+
2505+
#[derive(Subdiagnostic)]
2506+
#[multipart_suggestion(
2507+
parse_unexpected_expr_in_pat_replace_let_else_with_if_sugg,
2508+
applicability = "maybe-incorrect"
2509+
)]
2510+
pub(crate) struct UnexpectedExpressionInPatternReplaceLetElseWithIfSugg {
2511+
#[suggestion_part(code = "if {init} != {pat}")]
2512+
pub span: Span,
2513+
pub init: String,
2514+
pub pat: String,
2515+
}
2516+
24952517
#[derive(Diagnostic)]
24962518
#[diag(parse_unexpected_paren_in_range_pat)]
24972519
pub(crate) struct UnexpectedParenInRangePat {

‎compiler/rustc_parse/src/parser/pat.rs

Lines changed: 33 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,9 @@ use crate::errors::{
88
TopLevelOrPatternNotAllowed, TopLevelOrPatternNotAllowedSugg, TrailingVertNotAllowed,
99
UnexpectedExpressionInPattern, UnexpectedExpressionInPatternArmSugg,
1010
UnexpectedExpressionInPatternConstSugg, UnexpectedExpressionInPatternInlineConstSugg,
11-
UnexpectedLifetimeInPattern, UnexpectedParenInRangePat, UnexpectedParenInRangePatSugg,
11+
UnexpectedExpressionInPatternRemoveLetSugg,
12+
UnexpectedExpressionInPatternReplaceLetElseWithIfSugg, UnexpectedLifetimeInPattern,
13+
UnexpectedParenInRangePat, UnexpectedParenInRangePatSugg,
1214
UnexpectedVertVertBeforeFunctionParam, UnexpectedVertVertInPattern,
1315
};
1416
use crate::parser::expr::{could_be_unclosed_char_literal, DestructuredFloat, LhsExpr};
@@ -26,7 +28,7 @@ use rustc_errors::{Applicability, Diag, PResult, StashKey};
2628
use rustc_session::errors::ExprParenthesesNeeded;
2729
use rustc_span::source_map::{respan, Spanned};
2830
use rustc_span::symbol::{kw, sym, Ident};
29-
use rustc_span::{ErrorGuaranteed, Span};
31+
use rustc_span::{BytePos, ErrorGuaranteed, Span};
3032
use thin_vec::{thin_vec, ThinVec};
3133

3234
#[derive(PartialEq, Copy, Clone)]
@@ -497,15 +499,38 @@ impl<'a> Parser<'a> {
497499
err.span.replace(stash_span, expr_span);
498500

499501
if let StmtKind::Let(local) = &stmt.kind {
500-
// If we have an `ExprInPat`, the user tried to assign a value to another value,
501-
// which doesn't makes much sense.
502502
match &local.kind {
503-
LocalKind::Decl => {}
504-
LocalKind::Init(_) => {}
505-
LocalKind::InitElse(_, _) => {}
503+
// help: remove this `let`
504+
LocalKind::Decl | LocalKind::Init(_) => {
505+
err.subdiagnostic(
506+
UnexpectedExpressionInPatternRemoveLetSugg {
507+
// HACK: retrieves `let`'s span
508+
span: local
509+
.span
510+
.shrink_to_lo()
511+
.with_hi(local.span.lo() + BytePos(3)),
512+
},
513+
);
514+
}
515+
// help: replace the `let` with an `if`
516+
LocalKind::InitElse(init, els) => {
517+
err.subdiagnostic(
518+
UnexpectedExpressionInPatternReplaceLetElseWithIfSugg {
519+
span: local.span.shrink_to_lo().until(els.span),
520+
init: self
521+
.parser
522+
.span_to_snippet(init.span)
523+
.unwrap(),
524+
pat: self
525+
.parser
526+
.span_to_snippet(local.pat.span)
527+
.unwrap(),
528+
},
529+
);
530+
}
506531
}
507532
} else {
508-
// help: use an arm guard `if val == expr`
533+
// help: check the value in an arm guard
509534
if let Some(arm) = &self.arm {
510535
let (ident, ident_span) = match self.field {
511536
Some(field) => (

‎tests/ui/parser/bad-name.stderr

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,9 @@ error: expected a pattern, found an expression
88
--> $DIR/bad-name.rs:4:7
99
|
1010
LL | let x.y::<isize>.z foo;
11-
| ^^^^^^^^^^^^^^ arbitrary expressions are not allowed in patterns
11+
| --- ^^^^^^^^^^^^^^ arbitrary expressions are not allowed in patterns
12+
| |
13+
| help: remove this `let`
1214

1315
error: expected one of `(`, `.`, `::`, `:`, `;`, `=`, `?`, `|`, or an operator, found `foo`
1416
--> $DIR/bad-name.rs:4:22

‎tests/ui/parser/issues/issue-24197.stderr

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,9 @@ error: expected a pattern, found an expression
22
--> $DIR/issue-24197.rs:2:9
33
|
44
LL | let buf[0] = 0;
5-
| ^^^^^^ arbitrary expressions are not allowed in patterns
5+
| --- ^^^^^^ arbitrary expressions are not allowed in patterns
6+
| |
7+
| help: remove this `let`
68

79
error: aborting due to 1 previous error
810

‎tests/ui/parser/pat-lt-bracket-5.stderr

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,9 @@ error: expected a pattern, found an expression
22
--> $DIR/pat-lt-bracket-5.rs:2:9
33
|
44
LL | let v[0] = v[1];
5-
| ^^^^ arbitrary expressions are not allowed in patterns
5+
| --- ^^^^ arbitrary expressions are not allowed in patterns
6+
| |
7+
| help: remove this `let`
68

79
error[E0425]: cannot find value `v` in this scope
810
--> $DIR/pat-lt-bracket-5.rs:2:16

‎tests/ui/parser/pat-lt-bracket-6.stderr

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,9 @@ error: expected a pattern, found an expression
22
--> $DIR/pat-lt-bracket-6.rs:5:14
33
|
44
LL | let Test(&desc[..]) = x;
5-
| ^^^^^^^^^ arbitrary expressions are not allowed in patterns
5+
| --- ^^^^^^^^^ arbitrary expressions are not allowed in patterns
6+
| |
7+
| help: remove this `let`
68

79
error[E0308]: mismatched types
810
--> $DIR/pat-lt-bracket-6.rs:10:30

‎tests/ui/parser/pat-ranges-3.stderr

Lines changed: 6 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -2,13 +2,17 @@ error: expected a pattern range bound, found an expression
22
--> $DIR/pat-ranges-3.rs:4:16
33
|
44
LL | let 10 ..= 10 + 3 = 12;
5-
| ^^^^^^ arbitrary expressions are not allowed in patterns
5+
| --- ^^^^^^ arbitrary expressions are not allowed in patterns
6+
| |
7+
| help: remove this `let`
68

79
error: expected a pattern range bound, found an expression
810
--> $DIR/pat-ranges-3.rs:7:9
911
|
1012
LL | let 10 - 3 ..= 10 = 8;
11-
| ^^^^^^ arbitrary expressions are not allowed in patterns
13+
| --- ^^^^^^ arbitrary expressions are not allowed in patterns
14+
| |
15+
| help: remove this `let`
1216

1317
error: aborting due to 2 previous errors
1418

‎tests/ui/parser/recover/recover-pat-exprs.stderr

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -554,7 +554,9 @@ error: expected a pattern, found an expression
554554
--> $DIR/recover-pat-exprs.rs:71:9
555555
|
556556
LL | let 1 + 1 = 2;
557-
| ^^^^^ arbitrary expressions are not allowed in patterns
557+
| --- ^^^^^ arbitrary expressions are not allowed in patterns
558+
| |
559+
| help: remove this `let`
558560

559561
error: expected one of `)`, `,`, `@`, or `|`, found `*`
560562
--> $DIR/recover-pat-exprs.rs:74:28

‎tests/ui/parser/recover/recover-pat-lets.rs

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,7 @@
1+
fn main() {
2+
let x = Some(2);
3+
4+
let Some(1 + 1) = x else { //~ error: expected a pattern, found an expression
5+
return;
6+
};
7+
}

‎tests/ui/parser/recover/recover-pat-lets.stderr

Lines changed: 11 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,11 @@
1+
error: expected a pattern, found an expression
2+
--> $DIR/recover-pat-lets.rs:4:14
3+
|
4+
LL | let Some(1 + 1) = x else {
5+
| ---------^^^^^-----------
6+
| | |
7+
| | arbitrary expressions are not allowed in patterns
8+
| help: use an `if`: `if x != Some(1 + 1)`
9+
10+
error: aborting due to 1 previous error
11+

‎tests/ui/sized/ensure-overriding-bindings-in-pattern-with-ty-err-doesnt-ice.stderr

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,9 @@ error: expected a pattern, found an expression
22
--> $DIR/ensure-overriding-bindings-in-pattern-with-ty-err-doesnt-ice.rs:2:31
33
|
44
LL | let str::<{fn str() { let str::T>>::as_bytes; }}, T>::as_bytes;
5-
| ^^^^^^^^^^^^^^^^^^ arbitrary expressions are not allowed in patterns
5+
| --- ^^^^^^^^^^^^^^^^^^ arbitrary expressions are not allowed in patterns
6+
| |
7+
| help: remove this `let`
68

79
error[E0412]: cannot find type `T` in this scope
810
--> $DIR/ensure-overriding-bindings-in-pattern-with-ty-err-doesnt-ice.rs:2:55

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