Structured suggestion for extern crate foo when foo isn't resolved in import

estebank · estebank · commit 9a7979d6589b · 2024-07-24T21:04:54.000Z
When encountering a name in an import that could have come from a crate that wasn't imported, use a structured suggestion to suggest `extern crate foo;` pointing at the right place in the crate.

When encountering `_` in an import, do not suggest `extern crate _;`.

```
error[E0432]: unresolved import `spam`
  --&gt; $DIR/import-from-missing-star-3.rs:2:9
   |
LL |     use spam::*;
   |         ^^^^ maybe a missing crate `spam`?
   |
help: consider importing the `spam` crate
   |
LL + extern crate spam;
   |
```
diff --git a/compiler/rustc_resolve/src/def_collector.rs b/compiler/rustc_resolve/src/def_collector.rs
@@ -423,6 +423,7 @@ impl<'a, 'b, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'b, 'tcx> {
     }
 
     fn visit_crate(&mut self, krate: &'a Crate) {
+        self.resolver.current_crate_outer_attr_insert_span = Some(krate.spans.inject_use_span);
         if krate.is_placeholder {
             self.visit_macro_invoc(krate.id)
         } else {
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
@@ -2019,16 +2019,18 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                         Applicability::MaybeIncorrect,
                     )),
                 )
+            } else if ident.name == kw::Underscore {
+                (format!("`_` is not a valid crate or module name"), None)
             } else if self.tcx.sess.is_rust_2015() {
                 (
                     format!("maybe a missing crate `{ident}`?"),
-                    Some((
-                        vec![],
-                        format!(
-                            "consider adding `extern crate {ident}` to use the `{ident}` crate"
-                        ),
-                        Applicability::MaybeIncorrect,
-                    )),
+                    self.current_crate_outer_attr_insert_span.map(|sp| {
+                        (
+                            vec![(sp, format!("extern crate {ident};\n"))],
+                            format!("consider importing the `{ident}` crate"),
+                            Applicability::MaybeIncorrect,
+                        )
+                    }),
                 )
             } else {
                 (format!("could not find `{ident}` in the crate root"), None)
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
@@ -1176,6 +1176,10 @@ pub struct Resolver<'a, 'tcx> {
     /// Simplified analogue of module `resolutions` but in trait impls, excluding glob delegations.
     /// Needed because glob delegations exclude explicitly defined names.
     impl_binding_keys: FxHashMap<LocalDefId, FxHashSet<BindingKey>>,
+
+    /// This is the `Span` where an `extern crate foo;` suggestion would be inserted, if `foo`
+    /// could be a crate that wasn't imported. For diagnostics use only.
+    current_crate_outer_attr_insert_span: Option<Span>,
 }
 
 /// Nothing really interesting here; it just provides memory for the rest of the crate.
@@ -1521,6 +1525,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             glob_delegation_invoc_ids: Default::default(),
             impl_unexpanded_invocations: Default::default(),
             impl_binding_keys: Default::default(),
+            current_crate_outer_attr_insert_span: Default::default(),
         };
 
         let root_parent_scope = ParentScope::module(graph_root, &resolver);
diff --git a/tests/rustdoc-ui/intra-doc/unresolved-import-recovery.stderr b/tests/rustdoc-ui/intra-doc/unresolved-import-recovery.stderr
@@ -4,7 +4,10 @@ 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
+help: consider importing the `unresolved_crate` crate
+   |
+LL + extern crate unresolved_crate;
+   |
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/attributes/field-attributes-vis-unresolved.stderr b/tests/ui/attributes/field-attributes-vis-unresolved.stderr
@@ -4,15 +4,21 @@ 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
+help: consider importing the `nonexistent` crate
+   |
+LL + extern crate nonexistent;
+   |
 
 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
+help: consider importing the `nonexistent` crate
+   |
+LL + extern crate nonexistent;
+   |
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/error-codes/E0432.stderr b/tests/ui/error-codes/E0432.stderr
@@ -4,7 +4,10 @@ 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
+help: consider importing the `something` crate
+   |
+LL + extern crate something;
+   |
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/imports/import-from-missing-star-2.stderr b/tests/ui/imports/import-from-missing-star-2.stderr
@@ -4,7 +4,10 @@ error[E0432]: unresolved import `spam`
 LL |     use spam::*;
    |         ^^^^ maybe a missing crate `spam`?
    |
-   = help: consider adding `extern crate spam` to use the `spam` crate
+help: consider importing the `spam` crate
+   |
+LL + extern crate spam;
+   |
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/imports/import-from-missing-star-3.stderr b/tests/ui/imports/import-from-missing-star-3.stderr
@@ -4,15 +4,21 @@ error[E0432]: unresolved import `spam`
 LL |     use spam::*;
    |         ^^^^ maybe a missing crate `spam`?
    |
-   = help: consider adding `extern crate spam` to use the `spam` crate
+help: consider importing the `spam` crate
+   |
+LL + extern crate spam;
+   |
 
 error[E0432]: unresolved import `spam`
   --> $DIR/import-from-missing-star-3.rs:27:13
    |
 LL |         use spam::*;
    |             ^^^^ maybe a missing crate `spam`?
    |
-   = help: consider adding `extern crate spam` to use the `spam` crate
+help: consider importing the `spam` crate
+   |
+LL + extern crate spam;
+   |
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/imports/import-from-missing-star.stderr b/tests/ui/imports/import-from-missing-star.stderr
@@ -4,7 +4,10 @@ error[E0432]: unresolved import `spam`
 LL | use spam::*;
    |     ^^^^ maybe a missing crate `spam`?
    |
-   = help: consider adding `extern crate spam` to use the `spam` crate
+help: consider importing the `spam` crate
+   |
+LL + extern crate spam;
+   |
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/imports/import3.stderr b/tests/ui/imports/import3.stderr
@@ -4,7 +4,10 @@ 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
+help: consider importing the `main` crate
+   |
+LL + extern crate main;
+   |
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/imports/issue-109343.stderr b/tests/ui/imports/issue-109343.stderr
@@ -4,7 +4,10 @@ error[E0432]: unresolved import `unresolved`
 LL | pub use unresolved::f;
    |         ^^^^^^^^^^ maybe a missing crate `unresolved`?
    |
-   = help: consider adding `extern crate unresolved` to use the `unresolved` crate
+help: consider importing the `unresolved` crate
+   |
+LL + extern crate unresolved;
+   |
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/imports/issue-1697.stderr b/tests/ui/imports/issue-1697.stderr
@@ -4,7 +4,10 @@ error[E0432]: unresolved import `unresolved`
 LL | use unresolved::*;
    |     ^^^^^^^^^^ maybe a missing crate `unresolved`?
    |
-   = help: consider adding `extern crate unresolved` to use the `unresolved` crate
+help: consider importing the `unresolved` crate
+   |
+LL + extern crate unresolved;
+   |
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/imports/issue-33464.stderr b/tests/ui/imports/issue-33464.stderr
@@ -4,23 +4,32 @@ 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
+help: consider importing the `abc` crate
+   |
+LL + extern crate abc;
+   |
 
 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
+help: consider importing the `abc` crate
+   |
+LL + extern crate abc;
+   |
 
 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
+help: consider importing the `a_very_long_name` crate
+   |
+LL + extern crate a_very_long_name;
+   |
 
 error: aborting due to 3 previous errors
 
diff --git a/tests/ui/imports/issue-36881.stderr b/tests/ui/imports/issue-36881.stderr
@@ -4,7 +4,10 @@ error[E0432]: unresolved import `issue_36881_aux`
 LL |     use issue_36881_aux::Foo;
    |         ^^^^^^^^^^^^^^^ maybe a missing crate `issue_36881_aux`?
    |
-   = help: consider adding `extern crate issue_36881_aux` to use the `issue_36881_aux` crate
+help: consider importing the `issue_36881_aux` crate
+   |
+LL + extern crate issue_36881_aux;
+   |
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/imports/issue-37887.stderr b/tests/ui/imports/issue-37887.stderr
@@ -4,7 +4,10 @@ error[E0432]: unresolved import `test`
 LL |     use test::*;
    |         ^^^^ maybe a missing crate `test`?
    |
-   = help: consider adding `extern crate test` to use the `test` crate
+help: consider importing the `test` crate
+   |
+LL + extern crate test;
+   |
 
 error[E0658]: use of unstable library feature 'test'
   --> $DIR/issue-37887.rs:2:5
diff --git a/tests/ui/imports/issue-53269.stderr b/tests/ui/imports/issue-53269.stderr
@@ -4,7 +4,10 @@ error[E0432]: unresolved import `nonexistent_module`
 LL |     use nonexistent_module::mac;
    |         ^^^^^^^^^^^^^^^^^^ maybe a missing crate `nonexistent_module`?
    |
-   = help: consider adding `extern crate nonexistent_module` to use the `nonexistent_module` crate
+help: consider importing the `nonexistent_module` crate
+   |
+LL + extern crate nonexistent_module;
+   |
 
 error[E0659]: `mac` is ambiguous
   --> $DIR/issue-53269.rs:8:5
diff --git a/tests/ui/imports/issue-55457.stderr b/tests/ui/imports/issue-55457.stderr
@@ -13,7 +13,10 @@ error[E0432]: unresolved import `non_existent`
 LL | use non_existent::non_existent;
    |     ^^^^^^^^^^^^ maybe a missing crate `non_existent`?
    |
-   = help: consider adding `extern crate non_existent` to use the `non_existent` crate
+help: consider importing the `non_existent` crate
+   |
+LL + extern crate non_existent;
+   |
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/imports/issue-81413.stderr b/tests/ui/imports/issue-81413.stderr
@@ -4,7 +4,10 @@ error[E0432]: unresolved import `doesnt_exist`
 LL | pub use doesnt_exist::*;
    |         ^^^^^^^^^^^^ maybe a missing crate `doesnt_exist`?
    |
-   = help: consider adding `extern crate doesnt_exist` to use the `doesnt_exist` crate
+help: consider importing the `doesnt_exist` crate
+   |
+LL + extern crate doesnt_exist;
+   |
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/imports/tool-mod-child.stderr b/tests/ui/imports/tool-mod-child.stderr
@@ -4,31 +4,43 @@ error[E0433]: failed to resolve: maybe a missing crate `clippy`?
 LL | use clippy::a::b;
    |     ^^^^^^ maybe a missing crate `clippy`?
    |
-   = help: consider adding `extern crate clippy` to use the `clippy` crate
+help: consider importing the `clippy` crate
+   |
+LL + extern crate clippy;
+   |
 
 error[E0432]: unresolved import `clippy`
   --> $DIR/tool-mod-child.rs:1:5
    |
 LL | use clippy::a;
    |     ^^^^^^ maybe a missing crate `clippy`?
    |
-   = help: consider adding `extern crate clippy` to use the `clippy` crate
+help: consider importing the `clippy` crate
+   |
+LL + extern crate clippy;
+   |
 
 error[E0433]: failed to resolve: maybe a missing crate `rustdoc`?
   --> $DIR/tool-mod-child.rs:5:5
    |
 LL | use rustdoc::a::b;
    |     ^^^^^^^ maybe a missing crate `rustdoc`?
    |
-   = help: consider adding `extern crate rustdoc` to use the `rustdoc` crate
+help: consider importing the `rustdoc` crate
+   |
+LL + extern crate rustdoc;
+   |
 
 error[E0432]: unresolved import `rustdoc`
   --> $DIR/tool-mod-child.rs:4:5
    |
 LL | use rustdoc::a;
    |     ^^^^^^^ maybe a missing crate `rustdoc`?
    |
-   = help: consider adding `extern crate rustdoc` to use the `rustdoc` crate
+help: consider importing the `rustdoc` crate
+   |
+LL + extern crate rustdoc;
+   |
 
 error: aborting due to 4 previous errors
 
diff --git a/tests/ui/imports/unresolved-imports-used.stderr b/tests/ui/imports/unresolved-imports-used.stderr
@@ -16,31 +16,43 @@ error[E0432]: unresolved import `foo`
 LL | use foo::bar;
    |     ^^^ maybe a missing crate `foo`?
    |
-   = help: consider adding `extern crate foo` to use the `foo` crate
+help: consider importing the `foo` crate
+   |
+LL + extern crate foo;
+   |
 
 error[E0432]: unresolved import `baz`
   --> $DIR/unresolved-imports-used.rs:12:5
    |
 LL | use baz::*;
    |     ^^^ maybe a missing crate `baz`?
    |
-   = help: consider adding `extern crate baz` to use the `baz` crate
+help: consider importing the `baz` crate
+   |
+LL + extern crate baz;
+   |
 
 error[E0432]: unresolved import `foo2`
   --> $DIR/unresolved-imports-used.rs:14:5
    |
 LL | use foo2::bar2;
    |     ^^^^ maybe a missing crate `foo2`?
    |
-   = help: consider adding `extern crate foo2` to use the `foo2` crate
+help: consider importing the `foo2` crate
+   |
+LL + extern crate foo2;
+   |
 
 error[E0432]: unresolved import `baz2`
   --> $DIR/unresolved-imports-used.rs:15:5
    |
 LL | use baz2::*;
    |     ^^^^ maybe a missing crate `baz2`?
    |
-   = help: consider adding `extern crate baz2` to use the `baz2` crate
+help: consider importing the `baz2` crate
+   |
+LL + extern crate baz2;
+   |
 
 error[E0603]: function `quz` is private
   --> $DIR/unresolved-imports-used.rs:9:10
diff --git a/tests/ui/keyword/extern/keyword-extern-as-identifier-use.stderr b/tests/ui/keyword/extern/keyword-extern-as-identifier-use.stderr
@@ -15,7 +15,10 @@ error[E0432]: unresolved import `r#extern`
 LL | use extern::foo;
    |     ^^^^^^ maybe a missing crate `r#extern`?
    |
-   = help: consider adding `extern crate r#extern` to use the `r#extern` crate
+help: consider importing the `r#extern` crate
+   |
+LL + extern crate r#extern;
+   |
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/privacy/restricted/test.stderr b/tests/ui/privacy/restricted/test.stderr
diff --git a/tests/ui/resolve/editions-crate-root-2015.stderr b/tests/ui/resolve/editions-crate-root-2015.stderr
diff --git a/tests/ui/resolve/extern-prelude-fail.stderr b/tests/ui/resolve/extern-prelude-fail.stderr
diff --git a/tests/ui/resolve/issue-82865.stderr b/tests/ui/resolve/issue-82865.stderr
diff --git a/tests/ui/resolve/resolve-bad-visibility.stderr b/tests/ui/resolve/resolve-bad-visibility.stderr
diff --git a/tests/ui/underscore-imports/issue-110164.stderr b/tests/ui/underscore-imports/issue-110164.stderr
diff --git a/tests/ui/unresolved/unresolved-asterisk-imports.stderr b/tests/ui/unresolved/unresolved-asterisk-imports.stderr
diff --git a/tests/ui/unresolved/unresolved-import.rs b/tests/ui/unresolved/unresolved-import.rs
diff --git a/tests/ui/unresolved/unresolved-import.stderr b/tests/ui/unresolved/unresolved-import.stderr

Original file line number	Diff line number	Diff line change
`@@ -423,6 +423,7 @@ impl<'a, 'b, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'b, 'tcx> {`
`423`	`423`	`}`
`424`	`424`
`425`	`425`	`fn visit_crate(&mut self, krate: &'a Crate) {`
	`426`	`+ self.resolver.current_crate_outer_attr_insert_span = Some(krate.spans.inject_use_span);`
`426`	`427`	`if krate.is_placeholder {`
`427`	`428`	`self.visit_macro_invoc(krate.id)`
`428`	`429`	`} else {`