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Add note regarding parent module containing use statement. #42283

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May 30, 2017
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Add note regarding parent module containing use statement. #42283

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26 changes: 26 additions & 0 deletions src/librustc_resolve/diagnostics.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -838,6 +838,32 @@ trait Foo {

fn foo<T>(x: T) {} // ok!
```

Another case that causes this error is when a type is imported into a parent
module. To fix this, you can follow the suggestion and use File directly or
`use super::File;` which will import the types from the parent namespace. An
example that causes this error is below:

```compile_fail,E0412
use std::fs::File;

mod foo {
fn some_function(f: File) {}
}
```

```
use std::fs::File;

mod foo {
// either
use super::File;
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Currently CI failed with

[00:55:49] ---- /checkout/obj/build/x86_64-unknown-linux-gnu/test/error-index.md - Rust_Compiler_Error_Index (line 6486) stdout ----
[00:55:49] 	error[E0432]: unresolved import `super::File`
[00:55:49]  --> <anon>:6:9
[00:55:49]   |
[00:55:49] 6 |     use super::File;
[00:55:49]   |         ^^^^^^^^^^^ no `File` in the root

Dunno why, probably workaround it by adding a hidden # pub above the use std::fs::File?

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The problem here was that rustdoc auto-injects fn main surrounding this, so it was correct -- there was no File in root. I inserted an empty commented fn main to workaround this, so we should be fine now.

// or
// use std::fs::File;
fn foo(f: File) {}
}
# fn main() {} // don't insert it for us; that'll break imports
```
"##,

E0415: r##"
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