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Auto merge of #110041 - fmease:diag-sugg-adding-const-param, r=compiler-errors

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Suggest defining const parameter when appropriate

Helps a bit with #91119.
Following #105523's lead, I use placeholder `/* Type */` instead of `_` in the suggestion.
It should be easier for newcomers to parse.

`@rustbot` label A-diagnostics
r? diagnostics
This commit is contained in:
bors 2023-04-09 10:54:04 +00:00
commit 56e0626836
4 changed files with 100 additions and 7 deletions
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4
compiler/rustc_resolve/src/late.rs
View File

@ -3467,8 +3467,8 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
sugg.to_string(),
Applicability::MaybeIncorrect,
))
} else if res.is_none() && matches!(source, PathSource::Type) {
this.report_missing_type_error(path)
} else if res.is_none() && let PathSource::Type | PathSource::Expr(_) = source {
this.suggest_adding_generic_parameter(path, source)
} else {
None
};

15
compiler/rustc_resolve/src/late/diagnostics.rs
View File

@ -2110,9 +2110,10 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
}
}
pub(crate) fn report_missing_type_error(
pub(crate) fn suggest_adding_generic_parameter(
&self,
path: &[Segment],
source: PathSource<'_>,
) -> Option<(Span, &'static str, String, Applicability)> {
let (ident, span) = match path {
[segment]
@ -2148,7 +2149,6 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
// Without the 2nd `true`, we'd suggest `impl <T>` for `impl T` when a type `T` isn't found
| (Some(Item { kind: kind @ ItemKind::Impl(..), .. }), true, true)
| (Some(Item { kind, .. }), false, _) => {
// Likely missing type parameter.
if let Some(generics) = kind.generics() {
if span.overlaps(generics.span) {
// Avoid the following:
@ -2161,7 +2161,12 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
// | not found in this scope
return None;
}
let msg = "you might be missing a type parameter";
let (msg, sugg) = match source {
PathSource::Type => ("you might be missing a type parameter", ident),
PathSource::Expr(_) => ("you might be missing a const parameter", format!("const {ident}: /* Type */")),
_ => return None,
};
let (span, sugg) = if let [.., param] = &generics.params[..] {
let span = if let [.., bound] = &param.bounds[..] {
bound.span()
@ -2172,9 +2177,9 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
} else {
param.ident.span
};
(span, format!(", {}", ident))
(span, format!(", {sugg}"))
} else {
(generics.span, format!("<{}>", ident))
(generics.span, format!("<{sugg}>"))
};
// Do not suggest if this is coming from macro expansion.
if span.can_be_used_for_suggestions() {

24
tests/ui/missing/missing-items/missing-const-parameter.rs Normal file
View File

@ -0,0 +1,24 @@
struct Struct<const N: usize>;
impl Struct<{ N }> {}
//~^ ERROR cannot find value `N` in this scope
//~| HELP you might be missing a const parameter
fn func0(_: Struct<{ N }>) {}
//~^ ERROR cannot find value `N` in this scope
//~| HELP you might be missing a const parameter
fn func1(_: [u8; N]) {}
//~^ ERROR cannot find value `N` in this scope
//~| HELP you might be missing a const parameter
fn func2<T>(_: [T; N]) {}
//~^ ERROR cannot find value `N` in this scope
//~| HELP you might be missing a const parameter
struct Image<const R: usize>([[u32; C]; R]);
//~^ ERROR cannot find value `C` in this scope
//~| HELP a const parameter with a similar name exists
//~| HELP you might be missing a const parameter
fn main() {}

64
tests/ui/missing/missing-items/missing-const-parameter.stderr Normal file
View File

@ -0,0 +1,64 @@
error[E0425]: cannot find value `N` in this scope
--> $DIR/missing-const-parameter.rs:3:15
|
LL | impl Struct<{ N }> {}
| ^ not found in this scope
|
help: you might be missing a const parameter
|
LL | impl<const N: /* Type */> Struct<{ N }> {}
| +++++++++++++++++++++
error[E0425]: cannot find value `N` in this scope
--> $DIR/missing-const-parameter.rs:7:22
|
LL | fn func0(_: Struct<{ N }>) {}
| ^ not found in this scope
|
help: you might be missing a const parameter
|
LL | fn func0<const N: /* Type */>(_: Struct<{ N }>) {}
| +++++++++++++++++++++
error[E0425]: cannot find value `N` in this scope
--> $DIR/missing-const-parameter.rs:11:18
|
LL | fn func1(_: [u8; N]) {}
| ^ not found in this scope
|
help: you might be missing a const parameter
|
LL | fn func1<const N: /* Type */>(_: [u8; N]) {}
| +++++++++++++++++++++
error[E0425]: cannot find value `N` in this scope
--> $DIR/missing-const-parameter.rs:15:20
|
LL | fn func2<T>(_: [T; N]) {}
| ^ not found in this scope
|
help: you might be missing a const parameter
|
LL | fn func2<T, const N: /* Type */>(_: [T; N]) {}
| +++++++++++++++++++++
error[E0425]: cannot find value `C` in this scope
--> $DIR/missing-const-parameter.rs:19:37
|
LL | struct Image<const R: usize>([[u32; C]; R]);
| - ^
| |
| similarly named const parameter `R` defined here
|
help: a const parameter with a similar name exists
|
LL | struct Image<const R: usize>([[u32; R]; R]);
| ~
help: you might be missing a const parameter
|
LL | struct Image<const R: usize, const C: /* Type */>([[u32; C]; R]);
| +++++++++++++++++++++
error: aborting due to 5 previous errors
For more information about this error, try `rustc --explain E0425`.