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Rollup merge of #79851 - camelid:better-error-for-default-fn, r=davidtwco 

Clarify the 'default is only allowed on...' error

Code like

    impl Foo {
        default fn foo() {}
    }

will trigger the error

    error: `default` is only allowed on items in `impl` definitions
     --> src/lib.rs:5:5
      |
    5 |     default fn foo() {}
      |     -------^^^^^^^^^
      |     |
      |     `default` because of this

but that's very confusing! I *did* put it on an item in an impl!

So this commit changes the message to

    error: `default` is only allowed on items in trait impls
     --> src/lib.rs:5:5
      |
    5 |     default fn foo() {}
      |     -------^^^^^^^^^
      |     |
      |     `default` because of this
This commit is contained in:
Tyler Mandry 2020-12-10 21:33:10 -08:00 committed by GitHub
parent 17ec4b8258 4e21942ba4
commit dc90573454
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 13 additions and 13 deletions
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2
compiler/rustc_ast_passes/src/ast_validation.rs
View File

@ -400,7 +400,7 @@ impl<'a> AstValidator<'a> {
if let Defaultness::Default(def_span) = defaultness {
let span = self.session.source_map().guess_head_span(span);
self.err_handler()
.struct_span_err(span, "`default` is only allowed on items in `impl` definitions")
.struct_span_err(span, "`default` is only allowed on items in trait impls")
.span_label(def_span, "`default` because of this")
.emit();
}

12
src/test/ui/parser/trait-item-with-defaultness-fail-semantic.rs
View File

@ -3,10 +3,10 @@
fn main() {}
trait X {
default const A: u8; //~ ERROR `default` is only allowed on items in `impl` definitions
default const B: u8 = 0; //~ ERROR `default` is only allowed on items in `impl` definitions
default type D; //~ ERROR `default` is only allowed on items in `impl` definitions
default type C: Ord; //~ ERROR `default` is only allowed on items in `impl` definitions
default fn f1(); //~ ERROR `default` is only allowed on items in `impl` definitions
default fn f2() {} //~ ERROR `default` is only allowed on items in `impl` definitions
default const A: u8; //~ ERROR `default` is only allowed on items in trait impls
default const B: u8 = 0; //~ ERROR `default` is only allowed on items in trait impls
default type D; //~ ERROR `default` is only allowed on items in trait impls
default type C: Ord; //~ ERROR `default` is only allowed on items in trait impls
default fn f1(); //~ ERROR `default` is only allowed on items in trait impls
default fn f2() {} //~ ERROR `default` is only allowed on items in trait impls
}

12
src/test/ui/parser/trait-item-with-defaultness-fail-semantic.stderr
View File

@ -1,4 +1,4 @@
error: `default` is only allowed on items in `impl` definitions
error: `default` is only allowed on items in trait impls
--> $DIR/trait-item-with-defaultness-fail-semantic.rs:6:5
|
LL | default const A: u8;
@ -6,7 +6,7 @@ LL | default const A: u8;
| |
| `default` because of this
error: `default` is only allowed on items in `impl` definitions
error: `default` is only allowed on items in trait impls
--> $DIR/trait-item-with-defaultness-fail-semantic.rs:7:5
|
LL | default const B: u8 = 0;
@ -14,7 +14,7 @@ LL | default const B: u8 = 0;
| |
| `default` because of this
error: `default` is only allowed on items in `impl` definitions
error: `default` is only allowed on items in trait impls
--> $DIR/trait-item-with-defaultness-fail-semantic.rs:8:5
|
LL | default type D;
@ -22,7 +22,7 @@ LL | default type D;
| |
| `default` because of this
error: `default` is only allowed on items in `impl` definitions
error: `default` is only allowed on items in trait impls
--> $DIR/trait-item-with-defaultness-fail-semantic.rs:9:5
|
LL | default type C: Ord;
@ -30,7 +30,7 @@ LL | default type C: Ord;
| |
| `default` because of this
error: `default` is only allowed on items in `impl` definitions
error: `default` is only allowed on items in trait impls
--> $DIR/trait-item-with-defaultness-fail-semantic.rs:10:5
|
LL | default fn f1();
@ -38,7 +38,7 @@ LL | default fn f1();
| |
| `default` because of this
error: `default` is only allowed on items in `impl` definitions
error: `default` is only allowed on items in trait impls
--> $DIR/trait-item-with-defaultness-fail-semantic.rs:11:5
|
LL | default fn f2() {}