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Use the call site for the assign suggestion on macro-expanded types #158509

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Use the call site for the assign suggestion on macro-expanded types #158509

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4 changes: 2 additions & 2 deletions compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
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@fmease fmease Jun 28, 2026

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The suggestion is still incorrect for

macro_rules! make {
    () => { let x: vec![]; };
}

fn main() {
    make!();
}

namely

error: expected type, found associated function call
  --> u.rs:5:16
   |
 5 |         let x: vec![];
   |                ^^^^^^
...
12 |     make!();
   |     ------- in this macro invocation
   |
   = note: this error originates in the macro `vec` which comes from the expansion of the macro `make` (in Nightly builds, run with -Z macro-backtrace for more info)
help: use `=` if you meant to assign
   |
 5 -         let x: vec![];
 5 +         let  = : vec![];
   |

@fmease fmease Jun 28, 2026 •
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Moreover for

macro_rules! make {
    ($pat:pat, $ty:ty) => {
        let $pat: $ty;
    };
}

fn main() {
    make!(_, vec![]);
}

your branch now suggests

error: expected type, found associated function call
 --> u.rs:8:14
  |
8 |     make!(_, vec![]);
  |              ^^^^^^
  |
help: use `=` if you meant to assign
  |
8 -     make!(_, vec![]);
8 +     make!(_ = vec![]);
  |

main also emits an incorrect suggestion here but it's a different one.

@fmease fmease Jun 28, 2026

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What's more, for the following input

macro_rules! make {
    ($pat:pat) => {
        let $pat: Vec::new();
    };
}

fn main() {
    make!(_);
}

main correctly emits

error: expected type, found associated function call
 --> u.rs:3:19
  |
3 |         let $pat: Vec::new();
  |                   ^^^^^^^^^^
...
8 |     make!(_);
  |     -------- in this macro invocation
  |
  = note: this error originates in the macro `make` (in Nightly builds, run with -Z macro-backtrace for more info)
help: use `=` if you meant to assign
  |
3 -         let $pat: Vec::new();
3 +         let $pat = Vec::new();

but your branch incorrectly emits

error: expected type, found associated function call
 --> u.rs:3:19
  |
3 |         let $pat: Vec::new();
  |                   ^^^^^^^^^^
...
8 |     make!(_);
  |     -------- in this macro invocation
  |
  = note: this error originates in the macro `make` (in Nightly builds, run with -Z macro-backtrace for more info)
help: use `=` if you meant to assign
  |
8 -     make!(_);
8 +     make!( = );
  |

Original file line number Diff line number Diff line change
Expand Up @@ -3229,7 +3229,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
"expected type, found associated function call",
)
.with_span_suggestion_verbose(
stmt.pat.span.between(hir_ty.span),
stmt.pat.span.between(hir_ty.span.source_callsite()),
"use `=` if you meant to assign",
" = ".to_string(),
Applicability::MaybeIncorrect,
Expand All @@ -3255,7 +3255,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
"expected type, found associated function call",
)
.with_span_suggestion_verbose(
stmt.pat.span.between(hir_ty.span),
stmt.pat.span.between(hir_ty.span.source_callsite()),
"use `=` if you meant to assign",
" = ".to_string(),
Applicability::MaybeIncorrect,
Expand Down
1 change: 1 addition & 0 deletions tests/ui/suggestions/let-binding-init-expr-as-ty.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@ fn main() {
let x: S::new(..); //~ ERROR expected type, found associated function call
//~^ ERROR return type notation is experimental
let x: S::new(()); //~ ERROR expected type, found associated function call
let x: vec![]; //~ ERROR expected type, found associated function call

// Literals
let x: 42; //~ ERROR expected type, found `42`
Expand Down
24 changes: 18 additions & 6 deletions tests/ui/suggestions/let-binding-init-expr-as-ty.stderr
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
error: expected type, found `42`
--> $DIR/let-binding-init-expr-as-ty.rs:32:12
--> $DIR/let-binding-init-expr-as-ty.rs:33:12
|
LL | let x: 42;
| - ^^ expected type
Expand All @@ -13,7 +13,7 @@ LL + let x = 42;
|

error: expected type, found `""`
--> $DIR/let-binding-init-expr-as-ty.rs:33:12
--> $DIR/let-binding-init-expr-as-ty.rs:34:12
|
LL | let x: "";
| - ^^ expected type
Expand All @@ -39,7 +39,7 @@ LL + let foo = i32::from_be(num);
|

error[E0573]: expected type, found function `bar`
--> $DIR/let-binding-init-expr-as-ty.rs:36:12
--> $DIR/let-binding-init-expr-as-ty.rs:37:12
|
LL | let x: bar();
| ^^^^^ not a type
Expand All @@ -51,13 +51,13 @@ LL + let x = bar();
|

error[E0573]: expected type, found function `bar`
--> $DIR/let-binding-init-expr-as-ty.rs:37:12
--> $DIR/let-binding-init-expr-as-ty.rs:38:12
|
LL | let x: bar;
| ^^^ not a type

error[E0573]: expected type, found local variable `x`
--> $DIR/let-binding-init-expr-as-ty.rs:40:12
--> $DIR/let-binding-init-expr-as-ty.rs:41:12
|
LL | struct K(S::new(()));
| --------------------- similarly named struct `K` defined here
Expand Down Expand Up @@ -153,7 +153,19 @@ LL - let x: S::new(());
LL + let x = S::new(());
|

error: aborting due to 13 previous errors
error: expected type, found associated function call
--> $DIR/let-binding-init-expr-as-ty.rs:30:12
|
LL | let x: vec![];
| ^^^^^^
|
help: use `=` if you meant to assign
|
LL - let x: vec![];
LL + let x = vec![];
|

error: aborting due to 14 previous errors

Some errors have detailed explanations: E0573, E0658.
For more information about an error, try `rustc --explain E0573`.
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