Syntactically reject tuple index shorthands in struct patterns to fix a correctness regression
Split out of PR rust-lang/rust#154492. This fixes a correctness regression introduced in PR rust-lang/rust#81235 from 2021. Crater was run in my other PR and didn't report any real regressions (https://github.com/rust-lang/rust/pull/154492#issuecomment-4187544786); a rerun has been issued for a few spurious builds (https://github.com/rust-lang/rust/pull/154492#issuecomment-4237077272) but I'm certain it won't find anything either.
This is a theoretical breaking change that doesn't need any T-lang input IMHO since it's such a minute, niche and crystal clear bug that's not worth bothering them with (such a decision is not unprecedented). I'm adding it to the compatibility section of the release notes as is customary.
The Reference doesn't need updating since it didn't adopt this bug and thus accurately describes this part of the grammar as it used to be before 2021-02-23 and as it's meant to be.
The majority of the diff is doc comment additions & necessary UI test restructurings.
Move and clean up some ui test
`ui/reserved` -> `ui/keyword`
`ui/deref-patterns` -> `ui/pattern/deref-patterns`
`ui/unknown-unstable-lints` -> `ui/lint/unknown-lints`
Tests related to unknown_lints that were located above lint have also been moved to a subdirectory, and duplicate tests have been deleted.
And delete unnecessary `//@ check-fail`
r? Kivooeo
Move tests from `tests/ui/issues/` to appropriate directories
In this PR, I am moving the following test from `tests/ui/issues` directory to the appropriate directories, followed by the addition of issue links at the top and reblessing of the stderr files:
| old-name | new-sub-dir | new-name |
|-|-|-|
| `issue-29516.rs` | `auto-traits/` | `distinct-type-tuple-by-negative-impl.rs` |
| `issue-3874.rs` | `binding/` | `ref-in-let-lhs-in-field.rs` |
| `issue-32782.rs` | `feature-gates/` | `feature-gate-check-nested-macro-invocation.rs` |
| `issue-32782.stderr` | `feature-gates/` | `feature-gate-check-nested-macro-invocation.stderr` |
| `issue-5100.rs` | `pattern/` | `match-errors-derived-error-suppression.rs` |
| `issue-5100.stderr` | `pattern/` | `match-errors-derived-error-suppression.stderr` |
| `issue-21033.rs` | `pattern/` | `match-struct-var-having-boxed-field.rs` |
r? Kivooeo
r? Teapot4195
Update tracking issue number of future-incompatibility lint `unstable_syntax_pre_expansion`
Issue rust-lang/rust#65860 has never been a proper tracking issue, it has always been a normal issue that reported a pass→fail regression which was subsequently fixed and which elicited a discussion spanning 50 comments. Years later the formerly offending errors were reintroduced as warnings which link to said issue (see section *Pre-History* in issue rust-lang/rust#154045 for details).
A few weeks ago I closed this issue (https://github.com/rust-lang/rust/issues/65860#issuecomment-4083652176) in favor of a new super focused & structured tracking issue, rust-lang/rust#154045. That means people now have to jump through hoops to arrive at the new tracking issue which is less than ideal (it's very likely that this user had to do so: https://github.com/rust-lang/rust/issues/154045#issuecomment-4207339422), let's fix that.
Part of rust-lang/rust#154045.
Suggest using equality comparison instead of pattern matching on non-structural constant in pattern
When encountering a pattern containing a non-structural constant (not marked as `#[derive(PartialEq)]` to make it suitable for pattern matching, `C` in the examples below), we would previously not provide additional guidance. With this PR, the `help` in the following examples are added:
```
error: constant of non-structural type `partial_eq::S` in a pattern
--> $DIR/suggest_equality_comparison_instead_of_pattern_matching.rs:16:18
|
LL | struct S;
| -------- `partial_eq::S` must be annotated with `#[derive(PartialEq)]` to be usable in patterns
...
LL | const C: S = S;
| ---------- constant defined here
...
LL | Some(C) => {}
| ^ constant of non-structural type
|
note: the `PartialEq` trait must be derived, manual `impl`s are not sufficient; see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details
--> $DIR/suggest_equality_comparison_instead_of_pattern_matching.rs:5:5
|
LL | impl PartialEq<S> for S {
| ^^^^^^^^^^^^^^^^^^^^^^^
help: add a condition to the match arm checking for equality
|
LL - Some(C) => {}
LL + Some(binding) if binding == C => {}
|
```
```
error: constant of non-structural type `partial_eq::S` in a pattern
--> $DIR/suggest_equality_comparison_instead_of_pattern_matching.rs:22:18
|
LL | struct S;
| -------- `partial_eq::S` must be annotated with `#[derive(PartialEq)]` to be usable in patterns
...
LL | const C: S = S;
| ---------- constant defined here
...
LL | let Some(C) = Some(S) else { return; };
| ^ constant of non-structural type
|
note: the `PartialEq` trait must be derived, manual `impl`s are not sufficient; see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details
--> $DIR/suggest_equality_comparison_instead_of_pattern_matching.rs:5:5
|
LL | impl PartialEq<S> for S {
| ^^^^^^^^^^^^^^^^^^^^^^^
help: check for equality instead of pattern matching
|
LL - let Some(C) = Some(S) else { return; };
LL + if Some(C) == Some(S) { return; };
|
```
The suggestion accounts for a few conditions:
- if the type is not from the local crate and has no `PartialEq` impl, the user can't make it structural, so we don't provide the suggestion
- regardless of whether the type is local or remote, if it has a manual `PartialEq`, explain that with a derived `PartialEq` you could use equality
- if the type is local and has no impl, suggest adding a derived `PartialEq` and use equality check instead of pattern matching
- when suggesting equality, account for `if-let` to suggest chaining (edition dependent), `match` arm with a present `if` check, `match` arm without an existing `if` check
- when encountering `let-else`, we suggest turning it into an `if` expression instead (this doesn't check for additional bindings beyond the constant, which would suggest incorrect code in some more complex cases).
Fixrust-lang/rust#42753.
Guard patterns: lowering to THIR
This pr implements lowering of guard patterns to THIR
r? @Nadrieril
cc @max-niederman
Tracking issue: rust-lang/rust#129967
```
error: constant of non-structural type `partial_eq::S` in a pattern
--> $DIR/suggest_equality_comparison_instead_of_pattern_matching.rs:16:18
|
LL | struct S;
| -------- `partial_eq::S` must be annotated with `#[derive(PartialEq)]` to be usable in patterns
...
LL | const C: S = S;
| ---------- constant defined here
...
LL | Some(C) => {}
| ^ constant of non-structural type
|
note: the `PartialEq` trait must be derived, manual `impl`s are not sufficient; see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details
--> $DIR/suggest_equality_comparison_instead_of_pattern_matching.rs:5:5
|
LL | impl PartialEq<S> for S {
| ^^^^^^^^^^^^^^^^^^^^^^^
help: add a condition to the match arm checking for equality
|
LL - Some(C) => {}
LL + Some(binding) if binding == C => {}
|
```
stop marking `deref_patterns` as an incomplete feature
This PR removes the `incomplete_feature` warning for `deref_patterns`. The reason given for this in the tracking issue (rust-lang/rust#87121) was
> Per policy, the `incomplete_feature` is supposed to stay on until the feature has an accepted RFC. We're slowly working on writing up that RFC so it'll take some more time unfortunately.
>
> I don't know of any compiler crashes it causes today. The feature should be pretty usable.
However, I could not find any evidence of such a policy. The [lint documentation](https://doc.rust-lang.org/rustc/lints/listing/warn-by-default.html#incomplete-features) for `incomplete_features` also only mentions features that are more likely to cause errors.
There are also many other features without an RFC that are not considered incomplete, e.g. `macro_metavar_expr_concat`, `negative_impls` or `yeet_expr`.
The feature does not cause any known ICEs either.
The concrete motivation is to use this feature to replace `box_patterns` in the compiler and pave the way towards removing that legacy feature.
Remove "failed to resolve" and use the same format we use in other resolution errors "cannot find `name`".
```
error[E0433]: cannot find `nonexistent` in `existent`
--> $DIR/custom_attr_multisegment_error.rs:5:13
|
LL | #[existent::nonexistent]
| ^^^^^^^^^^^ could not find `nonexistent` in `existent`
```
Fix suppression of `unused_assignment` in binding of `unused_variable`
Unused assignments to an unused variable should trigger only the `unused_variables` lint and not also the `unused_assignments` lint. This was previously implemented by checking whether the span of the assignee was within the span of the binding pattern, however that failed to capture situations was imported from elsewhere (eg from the input tokenstream of a proc-macro that generates the binding pattern).
By comparing the span of the assignee to those of the variable introductions instead, a reported stable-to-stable regression is resolved.
This fix also impacted some other preexisting tests, which had (undesirably) been triggering both the `unused_variables` and `unused_assignments` lints on the same initializing assignment; those tests have therefore now been updated to expect only the former lint.
Fixesrust-lang/rust#151514
r? cjgillot (as author of reworked liveness testing in rust-lang/rust#142390)
Unused assignments to an unused variable should trigger only the
`unused_variables` lint and not also the `unused_assignments` lint.
This was previously implemented by checking whether the span of the
assignee was within the span of the binding pattern, however that failed
to capture situations was imported from elsewhere (eg from the input
tokenstream of a proc-macro that generates the binding pattern).
By comparing the span of the assignee to those of the variable
introductions instead, a reported stable-to-stable regression is
resolved.
This fix also impacted some other preexisting tests, which had
(undesirably) been triggering both the `unused_variables` and
`unused_assignments` lints on the same initializing assignment; those
tests have therefore now been updated to expect only the former lint.
Avoid ICEs after bad patterns, for the other syntactic variants
This PR introduces changes equivalent to the ones in rust-lang/rust#126320, but also for struct and tuple patterns, instead of tuple struct patterns only.
Fixesrust-lang/rust#150507.
Fix ICE by rejecting const blocks in patterns during AST lowering (closes#148138)
This PR fixes the ICE reported in rust-lang/rust#148138.
The root cause is that `const` blocks aren’t allowed in pattern position, but the AST lowering logic still attempted to create `PatExprKind::ConstBlock`, allowing invalid HIR to reach type checking and trigger a `span_bug!`.
Following the discussion in the issue, this patch removes the `ConstBlock` lowering path from `lower_expr_within_pat`. Any `ExprKind::ConstBlock` inside a pattern is now handled consistently with other invalid pattern expressions.
A new UI test is included to ensure the compiler reports a proper error and to prevent regressions.
Closesrust-lang/rust#148138.
This fixes the ICE reported by rejecting `const` blocks in
pattern position during AST lowering.
Previously, `ExprKind::ConstBlock` could reach HIR as `PatExprKind::ConstBlock`,
allowing invalid patterns to be type-checked and triggering an ICE.
This patch removes the lowering path for const blocks in patterns
and emits a proper diagnostic instead.
A new UI test is added to ensure the compiler reports a regular error
and to prevent regressions.
Suggest struct pattern when destructuring Range with .. syntax
implemented a new diagnostic in rustc_resolve to detect invalid range destructuring attempts (e.g., let start..end = range). The fix identifies when resolution fails for identifiers acting as range bounds specifically handling cases where bounds are parsed as expressions and suggests the correct struct pattern syntax (std::ops::Range { start, end }). This replaces confusing "cannot find value" errors with actionable help, verified by a new UI test covering various identifier names.
Fixesrust-lang/rust#149777
Tidying up tests/ui/issues 14 tests [5/N]
> [!NOTE]
> Intermediate commits are intended to help review, but will be squashed add comment commit prior to merge.
part of rust-lang/rust#133895
move `tests/ui/inherent-impls-overlap-check` to `tests/ui/duplicate/inherent-impls-overlap-check`.
r? Kivooeo
Tidying up tests/ui/issues 33 tests [4/N]
> [!NOTE]
> Intermediate commits are intended to help review, but will be squashed add comment commit prior to merge.
part of rust-lang/rust#133895
`tests/ui/compile-flags` split it into `tests/ui/compile-flags/invalid/` and `tests/ui/compile-flags/run-pass/`
r? Kivooeo
Jacob Pratt