diff options
9 files changed, 81 insertions, 23 deletions
diff --git a/compiler/rustc_error_codes/src/error_codes/E0404.md b/compiler/rustc_error_codes/src/error_codes/E0404.md index 1360cc99afc..d6fa51e618c 100644 --- a/compiler/rustc_error_codes/src/error_codes/E0404.md +++ b/compiler/rustc_error_codes/src/error_codes/E0404.md @@ -8,14 +8,15 @@ struct Foo; struct Bar; impl Foo for Bar {} // error: `Foo` is not a trait +fn baz<T: Foo>(t: T) {} // error: `Foo` is not a trait ``` Another erroneous code example: ```compile_fail,E0404 -struct Foo; +type Foo = Iterator<Item=String>; -fn bar<T: Foo>(t: T) {} // error: `Foo` is not a trait +fn bar<T: Foo>(t: T) {} // error: `Foo` is a type alias ``` Please verify that the trait's name was not misspelled or that the right @@ -30,14 +31,27 @@ struct Bar; impl Foo for Bar { // ok! // functions implementation } + +fn baz<T: Foo>(t: T) {} // ok! ``` -or: +Alternatively, you could introduce a new trait with your desired restrictions +as a super trait: ``` -trait Foo { - // some functions -} +# trait Foo {} +# struct Bar; +# impl Foo for Bar {} +trait Qux: Foo {} // Anything that implements Qux also needs to implement Foo +fn baz<T: Qux>(t: T) {} // also ok! +``` + +Finally, if you are on nightly and want to use a trait alias +instead of a type alias, you should use `#![feature(trait_alias)]`: + +``` +#![feature(trait_alias)] +trait Foo = Iterator<Item=String>; fn bar<T: Foo>(t: T) {} // ok! ``` diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs index 6fae6921fc9..e33c374f562 100644 --- a/compiler/rustc_resolve/src/late/diagnostics.rs +++ b/compiler/rustc_resolve/src/late/diagnostics.rs @@ -930,7 +930,14 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> { let msg = "you might have meant to use `#![feature(trait_alias)]` instead of a \ `type` alias"; if let Some(span) = self.def_span(def_id) { - err.span_help(span, msg); + if let Ok(snip) = self.r.session.source_map().span_to_snippet(span) { + // The span contains a type alias so we should be able to + // replace `type` with `trait`. + let snip = snip.replacen("type", "trait", 1); + err.span_suggestion(span, msg, snip, Applicability::MaybeIncorrect); + } else { + err.span_help(span, msg); + } } else { err.help(msg); } diff --git a/src/test/ui/codemap_tests/two_files.stderr b/src/test/ui/codemap_tests/two_files.stderr index de2ffc2e5dc..aff51ee9e2f 100644 --- a/src/test/ui/codemap_tests/two_files.stderr +++ b/src/test/ui/codemap_tests/two_files.stderr @@ -5,10 +5,9 @@ LL | impl Bar for Baz { } | ^^^ type aliases cannot be used as traits | help: you might have meant to use `#![feature(trait_alias)]` instead of a `type` alias - --> $DIR/two_files_data.rs:5:1 | -LL | type Bar = dyn Foo; - | ^^^^^^^^^^^^^^^^^^^ +LL | trait Bar = dyn Foo; + | error: aborting due to previous error diff --git a/src/test/ui/resolve/issue-3907.stderr b/src/test/ui/resolve/issue-3907.stderr index 4d0b0af58a3..6fc61cae843 100644 --- a/src/test/ui/resolve/issue-3907.stderr +++ b/src/test/ui/resolve/issue-3907.stderr @@ -5,10 +5,9 @@ LL | impl Foo for S { | ^^^ type aliases cannot be used as traits | help: you might have meant to use `#![feature(trait_alias)]` instead of a `type` alias - --> $DIR/issue-3907.rs:5:1 | -LL | type Foo = dyn issue_3907::Foo; - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +LL | trait Foo = dyn issue_3907::Foo; + | help: consider importing this trait instead | LL | use issue_3907::Foo; diff --git a/src/test/ui/resolve/issue-5035.stderr b/src/test/ui/resolve/issue-5035.stderr index 41dff2fe542..a8aa50b7c3a 100644 --- a/src/test/ui/resolve/issue-5035.stderr +++ b/src/test/ui/resolve/issue-5035.stderr @@ -11,16 +11,16 @@ LL | trait I {} | ------- similarly named trait `I` defined here LL | type K = dyn I; LL | impl K for isize {} - | ^ - | | - | type aliases cannot be used as traits - | help: a trait with a similar name exists: `I` + | ^ type aliases cannot be used as traits | help: you might have meant to use `#![feature(trait_alias)]` instead of a `type` alias - --> $DIR/issue-5035.rs:2:1 | -LL | type K = dyn I; - | ^^^^^^^^^^^^^^^ +LL | trait K = dyn I; + | +help: a trait with a similar name exists + | +LL | impl I for isize {} + | ^ error: aborting due to 2 previous errors diff --git a/src/test/ui/resolve/unboxed-closure-sugar-nonexistent-trait.stderr b/src/test/ui/resolve/unboxed-closure-sugar-nonexistent-trait.stderr index 2974d08eb23..8addc0303fb 100644 --- a/src/test/ui/resolve/unboxed-closure-sugar-nonexistent-trait.stderr +++ b/src/test/ui/resolve/unboxed-closure-sugar-nonexistent-trait.stderr @@ -11,10 +11,9 @@ LL | fn g<F:Typedef(isize) -> isize>(x: F) {} | ^^^^^^^^^^^^^^^^^^^^^^^ type aliases cannot be used as traits | help: you might have meant to use `#![feature(trait_alias)]` instead of a `type` alias - --> $DIR/unboxed-closure-sugar-nonexistent-trait.rs:4:1 | -LL | type Typedef = isize; - | ^^^^^^^^^^^^^^^^^^^^^ +LL | trait Typedef = isize; + | error: aborting due to 2 previous errors diff --git a/src/test/ui/traits/alias/suggest-trait-alias-instead-of-type.fixed b/src/test/ui/traits/alias/suggest-trait-alias-instead-of-type.fixed new file mode 100644 index 00000000000..8a94abaeb07 --- /dev/null +++ b/src/test/ui/traits/alias/suggest-trait-alias-instead-of-type.fixed @@ -0,0 +1,13 @@ +// Regression test of #43913. + +// run-rustfix + +#![feature(trait_alias)] +#![allow(bare_trait_objects, dead_code)] + +trait Strings = Iterator<Item=String>; + +struct Struct<S: Strings>(S); +//~^ ERROR: expected trait, found type alias `Strings` + +fn main() {} diff --git a/src/test/ui/traits/alias/suggest-trait-alias-instead-of-type.rs b/src/test/ui/traits/alias/suggest-trait-alias-instead-of-type.rs new file mode 100644 index 00000000000..40c678c281f --- /dev/null +++ b/src/test/ui/traits/alias/suggest-trait-alias-instead-of-type.rs @@ -0,0 +1,13 @@ +// Regression test of #43913. + +// run-rustfix + +#![feature(trait_alias)] +#![allow(bare_trait_objects, dead_code)] + +type Strings = Iterator<Item=String>; + +struct Struct<S: Strings>(S); +//~^ ERROR: expected trait, found type alias `Strings` + +fn main() {} diff --git a/src/test/ui/traits/alias/suggest-trait-alias-instead-of-type.stderr b/src/test/ui/traits/alias/suggest-trait-alias-instead-of-type.stderr new file mode 100644 index 00000000000..6e03eeada49 --- /dev/null +++ b/src/test/ui/traits/alias/suggest-trait-alias-instead-of-type.stderr @@ -0,0 +1,14 @@ +error[E0404]: expected trait, found type alias `Strings` + --> $DIR/suggest-trait-alias-instead-of-type.rs:10:18 + | +LL | struct Struct<S: Strings>(S); + | ^^^^^^^ type aliases cannot be used as traits + | +help: you might have meant to use `#![feature(trait_alias)]` instead of a `type` alias + | +LL | trait Strings = Iterator<Item=String>; + | + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0404`. |