When lowering paren surrounded pattern, keep outer span

estebank · estebank · commit 7c677f8653d8 · 2025-02-28T16:46:04.000Z
Parentheses surrounding patterns are not ketp in the HIR (and are warned against in the AST). In order to avoid having some suggestions break, we keep the outer span (including parentheses) when lowering the patterns.

```
error: a never pattern is always unreachable
  --&gt; $DIR/ICE-133117-duplicate-never-arm.rs:9:26
   |
LL |         (!|!) if true =&gt; {}
   |                          ^^ this will never be executed
   |
help: remove the match arm expression
   |
LL -         (!|!) if true =&gt; {}
LL +         (!|!),
   |
```
```
error[E0308]: mismatched types
  --&gt; $DIR/well-typed-edition-2024.rs:135:15
   |
LL |     let [&amp;mut &amp;(mut x)] = &amp;mut [&amp;0];
   |               ^^^^^^^^    --------- this expression has type `&amp;mut [&amp;{integer}; 1]`
   |               |
   |               expected integer, found `&amp;_`
   |
   = note:   expected type `{integer}`
           found reference `&amp;_`
help: consider removing `&amp;` from the pattern
   |
LL -     let [&amp;mut &amp;(mut x)] = &amp;mut [&amp;0];
LL +     let [&amp;mut (mut x)] = &amp;mut [&amp;0];
   |
```
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
@@ -689,7 +689,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     removal_span: if pat.span.eq_ctxt(arm.span) {
                         // - ! => {}
                         // + !,
-                        // FIXME: account for `(!|!)`, as pat.span ends *within* the parentheses.
                         pat.span.shrink_to_hi().with_hi(arm.span.hi())
                     } else {
                         // Subtly incorrect, but close enough if macros are involved.
diff --git a/compiler/rustc_ast_lowering/src/pat.rs b/compiler/rustc_ast_lowering/src/pat.rs
@@ -20,7 +20,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         self.arena.alloc(self.lower_pat_mut(pattern))
     }
 
-    fn lower_pat_mut(&mut self, mut pattern: &Pat) -> hir::Pat<'hir> {
+    fn lower_pat_mut(&mut self, outer_pattern: &Pat) -> hir::Pat<'hir> {
+        let mut pattern = outer_pattern;
         ensure_sufficient_stack(|| {
             // loop here to avoid recursion
             let pat_hir_id = self.lower_node_id(pattern.id);
@@ -147,7 +148,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 }
             };
 
-            self.pat_with_node_id_of(pattern, node, pat_hir_id)
+            self.pat_with_node_id_of(outer_pattern, node, pat_hir_id)
         })
     }
 
diff --git a/tests/ui/asm/naked-functions.stderr b/tests/ui/asm/naked-functions.stderr
@@ -89,10 +89,10 @@ LL |     &b: &i32,
    |     ^^
 
 error: patterns not allowed in naked function parameters
-  --> $DIR/naked-functions.rs:29:6
+  --> $DIR/naked-functions.rs:29:5
    |
 LL |     (None | Some(_)): Option<std::ptr::NonNull<u8>>,
-   |      ^^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^^^^
 
 error: patterns not allowed in naked function parameters
   --> $DIR/naked-functions.rs:31:5
diff --git a/tests/ui/closures/2229_closure_analysis/bad-pattern.stderr b/tests/ui/closures/2229_closure_analysis/bad-pattern.stderr
@@ -17,10 +17,10 @@ LL |         let _0 = v1;
    |             +
 
 error[E0005]: refutable pattern in local binding
-  --> $DIR/bad-pattern.rs:14:14
+  --> $DIR/bad-pattern.rs:14:13
    |
 LL |         let (0 | 1) = v1;
-   |              ^^^^^ pattern `2_u32..=u32::MAX` not covered
+   |             ^^^^^^^ pattern `2_u32..=u32::MAX` not covered
    |
    = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
    = note: for more information, visit https://doc.rust-lang.org/book/ch19-02-refutability.html
diff --git a/tests/ui/or-patterns/issue-69875-should-have-been-expanded-earlier-non-exhaustive.stderr b/tests/ui/or-patterns/issue-69875-should-have-been-expanded-earlier-non-exhaustive.stderr
@@ -1,8 +1,8 @@
 error[E0005]: refutable pattern in local binding
-  --> $DIR/issue-69875-should-have-been-expanded-earlier-non-exhaustive.rs:2:10
+  --> $DIR/issue-69875-should-have-been-expanded-earlier-non-exhaustive.rs:2:9
    |
 LL |     let (0 | (1 | 2)) = 0;
-   |          ^^^^^^^^^^^ patterns `i32::MIN..=-1_i32` and `3_i32..=i32::MAX` not covered
+   |         ^^^^^^^^^^^^^ patterns `i32::MIN..=-1_i32` and `3_i32..=i32::MAX` not covered
    |
    = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
    = note: for more information, visit https://doc.rust-lang.org/book/ch19-02-refutability.html
diff --git a/tests/ui/pattern/bindings-after-at/borrowck-pat-ref-mut-and-ref.stderr b/tests/ui/pattern/bindings-after-at/borrowck-pat-ref-mut-and-ref.stderr
@@ -10,18 +10,18 @@ error: cannot borrow value as mutable more than once at a time
   --> $DIR/borrowck-pat-ref-mut-and-ref.rs:33:9
    |
 LL |     let ref mut a @ (ref b @ ref mut c) = u(); // sub-in-sub
-   |         ^^^^^^^^^    -----   --------- value is mutably borrowed by `c` here
-   |         |            |
-   |         |            value is borrowed by `b` here
+   |         ^^^^^^^^^   ------   --------- value is mutably borrowed by `c` here
+   |         |           |
+   |         |           value is borrowed by `b` here
    |         value is mutably borrowed by `a` here
 
 error: cannot borrow value as mutable because it is also borrowed as immutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:33:22
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:33:21
    |
 LL |     let ref mut a @ (ref b @ ref mut c) = u(); // sub-in-sub
-   |                      ^^^^^   --------- value is mutably borrowed by `c` here
-   |                      |
-   |                      value is borrowed by `b` here
+   |                     ^^^^^^   --------- value is mutably borrowed by `c` here
+   |                     |
+   |                     value is borrowed by `b` here
 
 error: cannot borrow value as mutable because it is also borrowed as immutable
   --> $DIR/borrowck-pat-ref-mut-and-ref.rs:37:9
diff --git a/tests/ui/pattern/rfc-3627-match-ergonomics-2024/experimental/pattern-errors.classic2021.stderr b/tests/ui/pattern/rfc-3627-match-ergonomics-2024/experimental/pattern-errors.classic2021.stderr
@@ -211,7 +211,7 @@ LL |     let [&mut &(mut x)] = &[&mut 0];
 help: consider removing `&` from the pattern
    |
 LL -     let [&mut &(mut x)] = &[&mut 0];
-LL +     let [&mut mut x)] = &[&mut 0];
+LL +     let [&mut (mut x)] = &[&mut 0];
    |
 
 error: aborting due to 14 previous errors
diff --git a/tests/ui/pattern/rfc-3627-match-ergonomics-2024/experimental/pattern-errors.stable2021.stderr b/tests/ui/pattern/rfc-3627-match-ergonomics-2024/experimental/pattern-errors.stable2021.stderr
@@ -276,7 +276,7 @@ LL |     let [&mut &(mut x)] = &[&mut 0];
 help: consider removing `&` from the pattern
    |
 LL -     let [&mut &(mut x)] = &[&mut 0];
-LL +     let [&mut mut x)] = &[&mut 0];
+LL +     let [&mut (mut x)] = &[&mut 0];
    |
 
 error: aborting due to 21 previous errors
diff --git a/tests/ui/pattern/rfc-3627-match-ergonomics-2024/experimental/pattern-errors.structural2021.stderr b/tests/ui/pattern/rfc-3627-match-ergonomics-2024/experimental/pattern-errors.structural2021.stderr
@@ -302,7 +302,7 @@ LL |     let [&mut &(mut x)] = &[&mut 0];
 help: consider removing `&` from the pattern
    |
 LL -     let [&mut &(mut x)] = &[&mut 0];
-LL +     let [&mut mut x)] = &[&mut 0];
+LL +     let [&mut (mut x)] = &[&mut 0];
    |
 
 error: aborting due to 21 previous errors
diff --git a/tests/ui/pattern/rfc-3627-match-ergonomics-2024/experimental/pattern-errors.structural2024.stderr b/tests/ui/pattern/rfc-3627-match-ergonomics-2024/experimental/pattern-errors.structural2024.stderr
@@ -142,20 +142,20 @@ LL +     let &[&mut x] = &mut &mut [0];
    |
 
 error[E0658]: binding cannot be both mutable and by-reference
-  --> $DIR/pattern-errors.rs:102:12
+  --> $DIR/pattern-errors.rs:102:11
    |
 LL |     let [&(mut x)] = &[&0];
-   |            ^^^^
+   |           ^^^^^
    |
    = note: see issue #123076 <https://github.com/rust-lang/rust/issues/123076> for more information
    = help: add `#![feature(mut_ref)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0658]: binding cannot be both mutable and by-reference
-  --> $DIR/pattern-errors.rs:107:12
+  --> $DIR/pattern-errors.rs:107:11
    |
 LL |     let [&(mut x)] = &mut [&0];
-   |            ^^^^
+   |           ^^^^^
    |
    = note: see issue #123076 <https://github.com/rust-lang/rust/issues/123076> for more information
    = help: add `#![feature(mut_ref)]` to the crate attributes to enable
diff --git a/tests/ui/pattern/rfc-3627-match-ergonomics-2024/experimental/well-typed-edition-2024.classic2021.stderr b/tests/ui/pattern/rfc-3627-match-ergonomics-2024/experimental/well-typed-edition-2024.classic2021.stderr
@@ -107,7 +107,7 @@ LL |     let [&mut &(mut x)] = &mut [&0];
 help: consider removing `&` from the pattern
    |
 LL -     let [&mut &(mut x)] = &mut [&0];
-LL +     let [&mut mut x)] = &mut [&0];
+LL +     let [&mut (mut x)] = &mut [&0];
    |
 
 error[E0596]: cannot borrow data in a `&` reference as mutable
diff --git a/tests/ui/pattern/rfc-3627-match-ergonomics-2024/experimental/well-typed-edition-2024.structural2021.stderr b/tests/ui/pattern/rfc-3627-match-ergonomics-2024/experimental/well-typed-edition-2024.structural2021.stderr
@@ -107,7 +107,7 @@ LL |     let [&mut &(mut x)] = &mut [&0];
 help: consider removing `&` from the pattern
    |
 LL -     let [&mut &(mut x)] = &mut [&0];
-LL +     let [&mut mut x)] = &mut [&0];
+LL +     let [&mut (mut x)] = &mut [&0];
    |
 
 error[E0596]: cannot borrow data in a `&` reference as mutable
diff --git a/tests/ui/rfcs/rfc-0000-never_patterns/ICE-133063-never-arm-no-otherwise-block.stderr b/tests/ui/rfcs/rfc-0000-never_patterns/ICE-133063-never-arm-no-otherwise-block.stderr
@@ -7,7 +7,7 @@ LL |             (!|!) if false => {}
 help: remove the match arm expression
    |
 LL -             (!|!) if false => {}
-LL +             (!|!,
+LL +             (!|!),
    |
 
 error: aborting due to 1 previous error
diff --git a/tests/ui/rfcs/rfc-0000-never_patterns/ICE-133117-duplicate-never-arm.fixed b/tests/ui/rfcs/rfc-0000-never_patterns/ICE-133117-duplicate-never-arm.fixed
@@ -0,0 +1,14 @@
+//@ run-rustfix
+#![feature(never_type, never_patterns)]
+#![allow(incomplete_features, dead_code, unused_parens, unreachable_patterns)]
+
+enum Void {}
+
+fn foo(x: Void) {
+    match x {
+        (!|!), //~ ERROR a never pattern is always unreachable
+        (!|!), //~ ERROR a never pattern is always unreachable
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/rfcs/rfc-0000-never_patterns/ICE-133117-duplicate-never-arm.rs b/tests/ui/rfcs/rfc-0000-never_patterns/ICE-133117-duplicate-never-arm.rs
@@ -1,6 +1,6 @@
-#![feature(never_type)]
-#![feature(never_patterns)]
-#![allow(incomplete_features)]
+//@ run-rustfix
+#![feature(never_type, never_patterns)]
+#![allow(incomplete_features, dead_code, unused_parens, unreachable_patterns)]
 
 enum Void {}
 
diff --git a/tests/ui/rfcs/rfc-0000-never_patterns/ICE-133117-duplicate-never-arm.stderr b/tests/ui/rfcs/rfc-0000-never_patterns/ICE-133117-duplicate-never-arm.stderr
@@ -7,7 +7,7 @@ LL |         (!|!) if true => {}
 help: remove the match arm expression
    |
 LL -         (!|!) if true => {}
-LL +         (!|!,
+LL +         (!|!),
    |
 
 error: a never pattern is always unreachable
@@ -19,7 +19,7 @@ LL |         (!|!) if true => {}
 help: remove the match arm expression
    |
 LL -         (!|!) if true => {}
-LL +         (!|!,
+LL +         (!|!),
    |
 
 error: aborting due to 2 previous errors

Original file line number	Diff line number	Diff line change
`@@ -20,7 +20,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {`
`20`	`20`	`self.arena.alloc(self.lower_pat_mut(pattern))`
`21`	`21`	`}`
`22`	`22`
`23`		`- fn lower_pat_mut(&mut self, mut pattern: &Pat) -> hir::Pat<'hir> {`
	`23`	`+ fn lower_pat_mut(&mut self, outer_pattern: &Pat) -> hir::Pat<'hir> {`
	`24`	`+ let mut pattern = outer_pattern;`
`24`	`25`	`ensure_sufficient_stack(\|\| {`
`25`	`26`	`// loop here to avoid recursion`
`26`	`27`	`let pat_hir_id = self.lower_node_id(pattern.id);`
`@@ -147,7 +148,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {`
`147`	`148`	`}`
`148`	`149`	`};`
`149`	`150`
`150`		`- self.pat_with_node_id_of(pattern, node, pat_hir_id)`
	`151`	`+ self.pat_with_node_id_of(outer_pattern, node, pat_hir_id)`
`151`	`152`	`})`
`152`	`153`	`}`
`153`	`154`
Original file line number	Diff line number	Diff line change
`@@ -17,10 +17,10 @@ LL \| let _0 = v1;`
`17`	`17`	`\| +`
`18`	`18`
`19`	`19`	`error[E0005]: refutable pattern in local binding`
`20`		`- --> $DIR/bad-pattern.rs:14:14`
	`20`	`+ --> $DIR/bad-pattern.rs:14:13`
`21`	`21`	`\|`
`22`	`22`	`LL \| let (0 \| 1) = v1;`
`23`		- \| ^^^^^ pattern `2_u32..=u32::MAX` not covered
	`23`	+ \| ^^^^^^^ pattern `2_u32..=u32::MAX` not covered
`24`	`24`	`\|`
`25`	`25`	= note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
`26`	`26`	`= note: for more information, visit https://doc.rust-lang.org/book/ch19-02-refutability.html`
Original file line number	Diff line number	Diff line change
`@@ -1,8 +1,8 @@`
`1`	`1`	`error[E0005]: refutable pattern in local binding`
`2`		`- --> $DIR/issue-69875-should-have-been-expanded-earlier-non-exhaustive.rs:2:10`
	`2`	`+ --> $DIR/issue-69875-should-have-been-expanded-earlier-non-exhaustive.rs:2:9`
`3`	`3`	`\|`
`4`	`4`	`LL \| let (0 \| (1 \| 2)) = 0;`
`5`		- \| ^^^^^^^^^^^ patterns `i32::MIN..=-1_i32` and `3_i32..=i32::MAX` not covered
	`5`	+ \| ^^^^^^^^^^^^^ patterns `i32::MIN..=-1_i32` and `3_i32..=i32::MAX` not covered
`6`	`6`	`\|`
`7`	`7`	= note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
`8`	`8`	`= note: for more information, visit https://doc.rust-lang.org/book/ch19-02-refutability.html`
Original file line number	Diff line number	Diff line change
`@@ -211,7 +211,7 @@ LL \| let [&mut &(mut x)] = &[&mut 0];`
`211`	`211`	help: consider removing `&` from the pattern
`212`	`212`	`\|`
`213`	`213`	`LL - let [&mut &(mut x)] = &[&mut 0];`
`214`		`-LL + let [&mut mut x)] = &[&mut 0];`
	`214`	`+LL + let [&mut (mut x)] = &[&mut 0];`
`215`	`215`	`\|`
`216`	`216`
`217`	`217`	`error: aborting due to 14 previous errors`
Original file line number	Diff line number	Diff line change
`@@ -276,7 +276,7 @@ LL \| let [&mut &(mut x)] = &[&mut 0];`
`276`	`276`	help: consider removing `&` from the pattern
`277`	`277`	`\|`
`278`	`278`	`LL - let [&mut &(mut x)] = &[&mut 0];`
`279`		`-LL + let [&mut mut x)] = &[&mut 0];`
	`279`	`+LL + let [&mut (mut x)] = &[&mut 0];`
`280`	`280`	`\|`
`281`	`281`
`282`	`282`	`error: aborting due to 21 previous errors`
Original file line number	Diff line number	Diff line change
`@@ -302,7 +302,7 @@ LL \| let [&mut &(mut x)] = &[&mut 0];`
`302`	`302`	help: consider removing `&` from the pattern
`303`	`303`	`\|`
`304`	`304`	`LL - let [&mut &(mut x)] = &[&mut 0];`
`305`		`-LL + let [&mut mut x)] = &[&mut 0];`
	`305`	`+LL + let [&mut (mut x)] = &[&mut 0];`
`306`	`306`	`\|`
`307`	`307`
`308`	`308`	`error: aborting due to 21 previous errors`
Original file line number	Diff line number	Diff line change
`@@ -142,20 +142,20 @@ LL + let &[&mut x] = &mut &mut [0];`
`142`	`142`	`\|`
`143`	`143`
`144`	`144`	`error[E0658]: binding cannot be both mutable and by-reference`
`145`		`- --> $DIR/pattern-errors.rs:102:12`
	`145`	`+ --> $DIR/pattern-errors.rs:102:11`
`146`	`146`	`\|`
`147`	`147`	`LL \| let [&(mut x)] = &[&0];`
`148`		`- \| ^^^^`
	`148`	`+ \| ^^^^^`
`149`	`149`	`\|`
`150`	`150`	`= note: see issue #123076 <https://github.com/rust-lang/rust/issues/123076> for more information`
`151`	`151`	= help: add `#![feature(mut_ref)]` to the crate attributes to enable
`152`	`152`	`= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date`
`153`	`153`
`154`	`154`	`error[E0658]: binding cannot be both mutable and by-reference`
`155`		`- --> $DIR/pattern-errors.rs:107:12`
	`155`	`+ --> $DIR/pattern-errors.rs:107:11`
`156`	`156`	`\|`
`157`	`157`	`LL \| let [&(mut x)] = &mut [&0];`
`158`		`- \| ^^^^`
	`158`	`+ \| ^^^^^`
`159`	`159`	`\|`
`160`	`160`	`= note: see issue #123076 <https://github.com/rust-lang/rust/issues/123076> for more information`
`161`	`161`	= help: add `#![feature(mut_ref)]` to the crate attributes to enable
Original file line number	Diff line number	Diff line change
`@@ -107,7 +107,7 @@ LL \| let [&mut &(mut x)] = &mut [&0];`
`107`	`107`	help: consider removing `&` from the pattern
`108`	`108`	`\|`
`109`	`109`	`LL - let [&mut &(mut x)] = &mut [&0];`
`110`		`-LL + let [&mut mut x)] = &mut [&0];`
	`110`	`+LL + let [&mut (mut x)] = &mut [&0];`
`111`	`111`	`\|`
`112`	`112`
`113`	`113`	error[E0596]: cannot borrow data in a `&` reference as mutable
Original file line number	Diff line number	Diff line change
`@@ -7,7 +7,7 @@ LL \| (!\|!) if false => {}`
`7`	`7`	`help: remove the match arm expression`
`8`	`8`	`\|`
`9`	`9`	`LL - (!\|!) if false => {}`
`10`		`-LL + (!\|!,`
	`10`	`+LL + (!\|!),`
`11`	`11`	`\|`
`12`	`12`
`13`	`13`	`error: aborting due to 1 previous error`
Original file line number	Diff line number	Diff line change
`@@ -7,7 +7,7 @@ LL \| (!\|!) if true => {}`
`7`	`7`	`help: remove the match arm expression`
`8`	`8`	`\|`
`9`	`9`	`LL - (!\|!) if true => {}`
`10`		`-LL + (!\|!,`
	`10`	`+LL + (!\|!),`
`11`	`11`	`\|`
`12`	`12`
`13`	`13`	`error: a never pattern is always unreachable`
`@@ -19,7 +19,7 @@ LL \| (!\|!) if true => {}`
`19`	`19`	`help: remove the match arm expression`
`20`	`20`	`\|`
`21`	`21`	`LL - (!\|!) if true => {}`
`22`		`-LL + (!\|!,`
	`22`	`+LL + (!\|!),`
`23`	`23`	`\|`
`24`	`24`
`25`	`25`	`error: aborting due to 2 previous errors`