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Suggest use "{}", self.x instead of {self.x} when resolve x as field of self #141213

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Merged
merged 4 commits into from
May 21, 2025
Merged

Suggest use "{}", self.x instead of {self.x} when resolve x as field of self #141213

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fe0663c
Add test sugg-field-in-format-string-issue-141136
xizheyin May 18, 2025
9de7fff
Suggest use `"{}", self.x` instead of `{self.x}` when resolve `x` as …
xizheyin May 18, 2025
4ec9919
Add println! test for sugg-field-in-format-string-issue-141136
xizheyin May 20, 2025
84f67a5
Downgrade the confident of suggestion `available field in format stri…
xizheyin May 21, 2025
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24 changes: 18 additions & 6 deletions compiler/rustc_resolve/src/late/diagnostics.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -751,12 +751,24 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
match candidate {
AssocSuggestion::Field(field_span) => {
if self_is_available {
err.span_suggestion_verbose(
span.shrink_to_lo(),
"you might have meant to use the available field",
format!("{pre}self."),
Applicability::MachineApplicable,
);
let source_map = self.r.tcx.sess.source_map();
// check if the field is used in a format string, such as `"{x}"`
let field_is_format_named_arg = source_map
.span_to_source(span, |s, start, _| {
Ok(s.get(start - 1..start) == Some("{"))
});
if let Ok(true) = field_is_format_named_arg {
err.help(
format!("you might have meant to use the available field in a format string: `\"{{}}\", self.{}`", segment.ident.name),
);
} else {
err.span_suggestion_verbose(
span.shrink_to_lo(),
"you might have meant to use the available field",
format!("{pre}self."),
Applicability::MaybeIncorrect,
);
}
} else {
err.span_label(field_span, "a field by that name exists in `Self`");
}
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15 changes: 15 additions & 0 deletions tests/ui/resolve/suggestions/sugg-field-in-format-string-issue-141136.rs
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What happens on

struct Foo { x: i32 }

impl Foo {
    fn foo(&self) { _ = {x}; }
}

Does it essentially suggest fn foo(&self) { _ = "{}", self.x } (sic!)?

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I've opened issue #141350 to track this regression.

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It will give this message.

error[E0425]: cannot find value `x` in this scope
 --> src/main.rs:4:26
  |
4 |     fn foo(&self) { _ = {x}; }
  |                          ^
  |
  = help: you might have meant to use the available field in a format string: `"{}", self.x`

For further improvement, below two suggestions may be better?

The first suggestion is

help: you might have meant to use the available field if in a format string: `"{}", self.x`

and keep the origin suggestion

help: you might have meant to use the available field
  |
4 |     fn foo(&self) { _ = {self.x}; }
  |                          +++++

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Yeah, the message as emitted right now (on master) is not correct. It should indeed suggest you might have meant to use the available field as we do on beta/stable.

Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
struct Foo {
x: i32
}

impl Foo {
fn foo(&self) {
let _ = format!("{x}"); //~ ERROR cannot find value `x` in this scope [E0425]
let _ = format!("{x }"); //~ ERROR cannot find value `x` in this scope [E0425]
let _ = format!("{ x}"); //~ ERROR invalid format string: expected `}`, found `x`
let _ = format!("{}", x); //~ ERROR cannot find value `x` in this scope [E0425]
println!("{x}"); //~ ERROR cannot find value `x` in this scope [E0425]
}
}

fn main(){}
48 changes: 48 additions & 0 deletions tests/ui/resolve/suggestions/sugg-field-in-format-string-issue-141136.stderr
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Original file line number Diff line number Diff line change
@@ -0,0 +1,48 @@
error: invalid format string: expected `}`, found `x`
--> $DIR/sugg-field-in-format-string-issue-141136.rs:9:28
|
LL | let _ = format!("{ x}");
| - ^ expected `}` in format string
| |
| because of this opening brace
|
= note: if you intended to print `{`, you can escape it using `{{`

error[E0425]: cannot find value `x` in this scope
--> $DIR/sugg-field-in-format-string-issue-141136.rs:7:27
|
LL | let _ = format!("{x}");
| ^
|
= help: you might have meant to use the available field in a format string: `"{}", self.x`

error[E0425]: cannot find value `x` in this scope
--> $DIR/sugg-field-in-format-string-issue-141136.rs:8:27
|
LL | let _ = format!("{x }");
| ^^
|
= help: you might have meant to use the available field in a format string: `"{}", self.x`

error[E0425]: cannot find value `x` in this scope
--> $DIR/sugg-field-in-format-string-issue-141136.rs:10:31
|
LL | let _ = format!("{}", x);
| ^
|
help: you might have meant to use the available field
|
LL | let _ = format!("{}", self.x);
| +++++

error[E0425]: cannot find value `x` in this scope
--> $DIR/sugg-field-in-format-string-issue-141136.rs:11:20
|
LL | println!("{x}");
| ^
|
= help: you might have meant to use the available field in a format string: `"{}", self.x`

error: aborting due to 5 previous errors

For more information about this error, try `rustc --explain E0425`.
12 changes: 2 additions & 10 deletions tests/ui/resolve/typo-suggestion-for-variable-with-name-similar-to-struct-field.stderr
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Expand Up @@ -20,17 +20,9 @@ error[E0425]: cannot find value `config` in this scope
--> $DIR/typo-suggestion-for-variable-with-name-similar-to-struct-field.rs:15:20
|
LL | println!("{config}");
| ^^^^^^
|
help: you might have meant to use the available field
|
LL | println!("{self.config}");
| +++++
help: a local variable with a similar name exists
|
LL - println!("{config}");
LL + println!("{cofig}");
| ^^^^^^ help: a local variable with a similar name exists: `cofig`
|
= help: you might have meant to use the available field in a format string: `"{}", self.config`

error[E0425]: cannot find value `bah` in this scope
--> $DIR/typo-suggestion-for-variable-with-name-similar-to-struct-field.rs:33:9
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