Add a suggestion when using a type alias instead of trait alias
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8 changed files with 61 additions and 17 deletions
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@ -928,7 +928,14 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
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let msg = "you might have meant to use `#![feature(trait_alias)]` instead of a \
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`type` alias";
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if let Some(span) = self.def_span(def_id) {
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if let Ok(snip) = self.r.session.source_map().span_to_snippet(span) {
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// The span contains a type alias so we should be able to
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// replace `type` with `trait`.
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let snip = snip.replacen("type", "trait", 1);
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err.span_suggestion(span, msg, snip, Applicability::MaybeIncorrect);
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} else {
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err.span_help(span, msg);
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}
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} else {
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err.help(msg);
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}
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@ -5,10 +5,9 @@ LL | impl Bar for Baz { }
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| ^^^ type aliases cannot be used as traits
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help: you might have meant to use `#![feature(trait_alias)]` instead of a `type` alias
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--> $DIR/two_files_data.rs:5:1
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LL | type Bar = dyn Foo;
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| ^^^^^^^^^^^^^^^^^^^
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LL | trait Bar = dyn Foo;
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error: aborting due to previous error
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@ -5,10 +5,9 @@ LL | impl Foo for S {
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| ^^^ type aliases cannot be used as traits
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help: you might have meant to use `#![feature(trait_alias)]` instead of a `type` alias
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--> $DIR/issue-3907.rs:5:1
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LL | type Foo = dyn issue_3907::Foo;
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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LL | trait Foo = dyn issue_3907::Foo;
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help: consider importing this trait instead
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LL | use issue_3907::Foo;
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@ -11,16 +11,16 @@ LL | trait I {}
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| ------- similarly named trait `I` defined here
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LL | type K = dyn I;
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LL | impl K for isize {}
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| ^
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| |
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| type aliases cannot be used as traits
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| help: a trait with a similar name exists: `I`
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| ^ type aliases cannot be used as traits
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help: you might have meant to use `#![feature(trait_alias)]` instead of a `type` alias
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--> $DIR/issue-5035.rs:2:1
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LL | type K = dyn I;
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| ^^^^^^^^^^^^^^^
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LL | trait K = dyn I;
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help: a trait with a similar name exists
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LL | impl I for isize {}
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| ^
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error: aborting due to 2 previous errors
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@ -11,10 +11,9 @@ LL | fn g<F:Typedef(isize) -> isize>(x: F) {}
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| ^^^^^^^^^^^^^^^^^^^^^^^ type aliases cannot be used as traits
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help: you might have meant to use `#![feature(trait_alias)]` instead of a `type` alias
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--> $DIR/unboxed-closure-sugar-nonexistent-trait.rs:4:1
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LL | type Typedef = isize;
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| ^^^^^^^^^^^^^^^^^^^^^
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LL | trait Typedef = isize;
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error: aborting due to 2 previous errors
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@ -0,0 +1,13 @@
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// Regression test of #43913.
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// run-rustfix
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#![feature(trait_alias)]
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#![allow(bare_trait_objects, dead_code)]
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trait Strings = Iterator<Item=String>;
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struct Struct<S: Strings>(S);
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//~^ ERROR: expected trait, found type alias `Strings`
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fn main() {}
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@ -0,0 +1,13 @@
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// Regression test of #43913.
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// run-rustfix
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#![feature(trait_alias)]
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#![allow(bare_trait_objects, dead_code)]
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type Strings = Iterator<Item=String>;
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struct Struct<S: Strings>(S);
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//~^ ERROR: expected trait, found type alias `Strings`
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fn main() {}
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@ -0,0 +1,14 @@
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error[E0404]: expected trait, found type alias `Strings`
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--> $DIR/suggest-trait-alias-instead-of-type.rs:10:18
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LL | struct Struct<S: Strings>(S);
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| ^^^^^^^ type aliases cannot be used as traits
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help: you might have meant to use `#![feature(trait_alias)]` instead of a `type` alias
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LL | trait Strings = Iterator<Item=String>;
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error: aborting due to previous error
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For more information about this error, try `rustc --explain E0404`.
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