Suggest `let` or `==` on typo'd let-chain #118191

estebank · 2023-11-23T00:27:52Z

When encountering a bare assignment in a let-chain, suggest turning the
assignment into a let expression or an equality check.

error: expected expression, found `let` statement
  --> $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
help: you might have meant to continue the let-chain
   |
LL |     if let x = 1 && let i = 2 {}
   |                     +++
help: you might have meant to compare for equality
   |
LL |     if let x = 1 && i == 2 {}
   |                        +

rustbot · 2023-11-23T00:28:00Z

r? @cjgillot

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compiler-errors · 2023-11-23T00:32:50Z

compiler/rustc_parse/src/parser/expr.rs

-        CondChecker { parser: self, forbid_let_reason: None }.visit_expr(&mut cond);
+        let mut checker = CondChecker::new(self);
+        checker.visit_expr(&mut cond);
+        if checker.seen_missing_let {


Instead of maintaining global state here, why don't we just bubble up a parse error to stop compilation, or taint the AST with an ExprKind::Error?

compiler/rustc_session/src/parse.rs

compiler-errors · 2023-11-23T00:34:00Z

compiler/rustc_session/src/parse.rs

+    /// we should do something that is scope-based, instead of crate-global.
+    pub silence_resolve_errors: Lock<bool>,
+    /// Track parse errors that suggests changing an assignment to be an equality check.
+    pub silence_missing_comparison: Lock<Vec<Span>>,


This one will be trickier to write in a nice way :-/

.any(|(sp, _)| sp == span), or maybe use a HashMap?

tests/ui/expr/if/bad-if-let-suggestion.rs

compiler-errors · 2023-11-23T00:42:35Z

Also, this PR silences type errors along with resolver errors. Can the title of the PR be updated to make this apparent?

compiler-errors · 2023-11-23T00:47:07Z

compiler/rustc_parse/src/parser/expr.rs

+        checker.visit_expr(&mut cond);
+        if checker.seen_missing_let.is_some() {
+            // Avoid unnecessary resolve errors as we know we'll have some.
+            *self.sess.silence_resolve_errors.borrow_mut() = checker.seen_missing_let;
+        }
+        self.sess.silence_missing_comparison.borrow_mut().append(&mut checker.seen_comparison);


Instead of having global state here, why not just return Err(..)? That should halt parsing.

When encountering a bare assignment in a let-chain, suggest turning the assignment into a `let` expression or an equality check. ``` error: expected expression, found `let` statement --> $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 help: you might have meant to continue the let-chain | LL | if let x = 1 && let i = 2 {} | +++ help: you might have meant to compare for equality | LL | if let x = 1 && i == 2 {} | + ```

estebank · 2023-11-28T18:09:42Z

Removed the subsequent silencing logic. There are several cases of resolve errors that I want to address and it's likely better to do that in a different PR.

compiler-errors · 2023-11-28T19:53:44Z

@bors r+

bors · 2023-11-28T19:53:47Z

📌 Commit 55e4e3e has been approved by compiler-errors

It is now in the queue for this repository.

compiler-errors · 2023-11-28T22:33:17Z

@bors rollup

…r-errors Suggest `let` or `==` on typo'd let-chain When encountering a bare assignment in a let-chain, suggest turning the assignment into a `let` expression or an equality check. ``` error: expected expression, found `let` statement --> $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 help: you might have meant to continue the let-chain | LL | if let x = 1 && let i = 2 {} | +++ help: you might have meant to compare for equality | LL | if let x = 1 && i == 2 {} | + ```

…iaskrgr Rollup of 7 pull requests Successful merges: - rust-lang#118157 (Add `never_patterns` feature gate) - rust-lang#118191 (Suggest `let` or `==` on typo'd let-chain) - rust-lang#118231 (also add is_empty to const raw slices) - rust-lang#118333 (Print list of missing target features when calling a function with target features outside an unsafe block) - rust-lang#118426 (ConstProp: Correctly remove const if unknown value assigned to it.) - rust-lang#118428 (rustdoc: Move `AssocItemRender` and `RenderMode` to `html::render`.) - rust-lang#118438 (Update nto-qnx.md) Failed merges: - rust-lang#118268 (Pretty print `Fn<(..., ...)>` trait refs with parentheses (almost) always) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#118191 - estebank:let-chain-typo, r=compiler-errors Suggest `let` or `==` on typo'd let-chain When encountering a bare assignment in a let-chain, suggest turning the assignment into a `let` expression or an equality check. ``` error: expected expression, found `let` statement --> $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 help: you might have meant to continue the let-chain | LL | if let x = 1 && let i = 2 {} | +++ help: you might have meant to compare for equality | LL | if let x = 1 && i == 2 {} | + ```

rustbot assigned cjgillot Nov 23, 2023

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Nov 23, 2023

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estebank changed the title ~~Suggest let or == and silence resolve errors on typo'd let-chain~~ Suggest let or == and silence resolve and type errors on typo'd let-chain Nov 23, 2023

compiler-errors reviewed Nov 23, 2023

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estebank force-pushed the let-chain-typo branch from 6944bff to 55e4e3e Compare November 28, 2023 18:08

estebank changed the title ~~Suggest let or == and silence resolve and type errors on typo'd let-chain~~ Suggest let or == on typo'd let-chain Nov 28, 2023

compiler-errors assigned compiler-errors and unassigned cjgillot Nov 28, 2023

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 28, 2023

matthiaskrgr mentioned this pull request Nov 29, 2023

Rollup of 6 pull requests #118432

Closed

This was referenced Nov 29, 2023

Rollup of 6 pull requests #118435

Closed

Rollup of 7 pull requests #118443

Merged

bors merged commit aab61d0 into rust-lang:master Nov 29, 2023
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rustbot added this to the 1.76.0 milestone Nov 29, 2023

est31 mentioned this pull request Nov 10, 2024

Stabilize let chains in the 2024 edition #132833

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Suggest `let` or `==` on typo'd let-chain #118191

Suggest `let` or `==` on typo'd let-chain #118191

estebank commented Nov 23, 2023 •

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Suggest let or == on typo'd let-chain #118191

Suggest let or == on typo'd let-chain #118191

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Suggest `let` or `==` on typo'd let-chain #118191

Suggest `let` or `==` on typo'd let-chain #118191

estebank commented Nov 23, 2023 •

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