Rollup merge of rust-lang#97264 - TaKO8Ki:suggest-extern-crate-when-failing-to-resolve-use-crate, r=estebank

Suggest `extern crate foo` when failing to resolve `use foo` closes rust-lang#97095 r? ``@estebank``

Author: matthiaskrgr

compiler/rustc_resolve/src/diagnostics.rs

@@ -1839,9 +1839,18 @@ impl<'a> Resolver<'a> {
  )),
  )
  } else if self.session.edition() == Edition::Edition2015 {
- (format!("maybe a missing crate `{}`?", ident), None)
+ (
+ format!("maybe a missing crate `{ident}`?"),
+ Some((
+ vec![],
+ format!(
+ "consider adding `extern crate {ident}` to use the `{ident}` crate"
+ ),
+ Applicability::MaybeIncorrect,
+ )),
+ )
  } else {
- (format!("could not find `{}` in the crate root", ident), None)
+ (format!("could not find `{ident}` in the crate root"), None)
  }
  } else if i > 0 {
  let parent = path[i - 1].ident.name;
@@ -1852,7 +1861,7 @@ impl<'a> Resolver<'a> {
  "the list of imported crates".to_owned()
  }
  kw::PathRoot | kw::Crate => "the crate root".to_owned(),
- _ => format!("`{}`", parent),
+ _ => format!("`{parent}`"),
  };
 
  let mut msg = format!("could not find `{}` in {}", ident, parent);

compiler/rustc_resolve/src/imports.rs

@@ -475,6 +475,10 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
  }
 
  if let Some((suggestions, msg, applicability)) = err.suggestion {
+ if suggestions.is_empty() {
+ diag.help(&msg);
+ continue;
+ }
  diag.multipart_suggestion(&msg, suggestions, applicability);
  }
  }

src/test/rustdoc-ui/intra-doc/unresolved-import-recovery.stderr

@@ -3,6 +3,8 @@ error[E0433]: failed to resolve: maybe a missing crate `unresolved_crate`?
  |
 LL | use unresolved_crate::module::Name;
  | ^^^^^^^^^^^^^^^^ maybe a missing crate `unresolved_crate`?
+ |
+ = help: consider adding `extern crate unresolved_crate` to use the `unresolved_crate` crate
 
 error: Compilation failed, aborting rustdoc
 

src/test/rustdoc-ui/issue-61732.stderr

@@ -3,6 +3,8 @@ error[E0433]: failed to resolve: maybe a missing crate `r#mod`?
  |
 LL | pub(in crate::r#mod) fn main() {}
  | ^^^^^ maybe a missing crate `r#mod`?
+ |
+ = help: consider adding `extern crate r#mod` to use the `r#mod` crate
 
 error: Compilation failed, aborting rustdoc
 

src/test/ui/attributes/field-attributes-vis-unresolved.stderr

@@ -3,12 +3,16 @@ error[E0433]: failed to resolve: maybe a missing crate `nonexistent`?
  |
 LL | pub(in nonexistent) field: u8
  | ^^^^^^^^^^^ maybe a missing crate `nonexistent`?
+ |
+ = help: consider adding `extern crate nonexistent` to use the `nonexistent` crate
 
 error[E0433]: failed to resolve: maybe a missing crate `nonexistent`?
  --> $DIR/field-attributes-vis-unresolved.rs:22:12
  |
 LL | pub(in nonexistent) u8
  | ^^^^^^^^^^^ maybe a missing crate `nonexistent`?
+ |
+ = help: consider adding `extern crate nonexistent` to use the `nonexistent` crate
 
 error: aborting due to 2 previous errors
 

src/test/ui/error-codes/E0432.stderr

@@ -3,6 +3,8 @@ error[E0432]: unresolved import `something`
  |
 LL | use something::Foo;
  | ^^^^^^^^^ maybe a missing crate `something`?
+ |
+ = help: consider adding `extern crate something` to use the `something` crate
 
 error: aborting due to previous error
 

src/test/ui/feature-gates/feature-gate-extern_absolute_paths.stderr

@@ -3,12 +3,16 @@ error[E0432]: unresolved import `core`
  |
 LL | use core::default;
  | ^^^^ maybe a missing crate `core`?
+ |
+ = help: consider adding `extern crate core` to use the `core` crate
 
 error[E0433]: failed to resolve: maybe a missing crate `core`?
  --> $DIR/feature-gate-extern_absolute_paths.rs:4:19
  |
 LL | let _: u8 = ::core::default::Default();
  | ^^^^ maybe a missing crate `core`?
+ |
+ = help: consider adding `extern crate core` to use the `core` crate
 
 error: aborting due to 2 previous errors
 

src/test/ui/imports/import3.stderr

@@ -3,6 +3,8 @@ error[E0432]: unresolved import `main`
  |
 LL | use main::bar;
  | ^^^^ maybe a missing crate `main`?
+ |
+ = help: consider adding `extern crate main` to use the `main` crate
 
 error: aborting due to previous error
 

src/test/ui/imports/issue-1697.stderr

@@ -3,6 +3,8 @@ error[E0432]: unresolved import `unresolved`
  |
 LL | use unresolved::*;
  | ^^^^^^^^^^ maybe a missing crate `unresolved`?
+ |
+ = help: consider adding `extern crate unresolved` to use the `unresolved` crate
 
 error: aborting due to previous error
 

src/test/ui/imports/issue-33464.stderr

@@ -3,18 +3,24 @@ error[E0432]: unresolved import `abc`
  |
 LL | use abc::one_el;
  | ^^^ maybe a missing crate `abc`?
+ |
+ = help: consider adding `extern crate abc` to use the `abc` crate
 
 error[E0432]: unresolved import `abc`
  --> $DIR/issue-33464.rs:5:5
  |
 LL | use abc::{a, bbb, cccccc};
  | ^^^ maybe a missing crate `abc`?
+ |
+ = help: consider adding `extern crate abc` to use the `abc` crate
 
 error[E0432]: unresolved import `a_very_long_name`
  --> $DIR/issue-33464.rs:7:5
  |
 LL | use a_very_long_name::{el, el2};
  | ^^^^^^^^^^^^^^^^ maybe a missing crate `a_very_long_name`?
+ |
+ = help: consider adding `extern crate a_very_long_name` to use the `a_very_long_name` crate
 
 error: aborting due to 3 previous errors