Use cfg_attr AST placeholder AST cfg_attr_trace for diagnostics

estebank · estebank · commit f80e3ac4ed1e · 2025-05-29T10:24:23.000Z
PR 138515, we insert a placeholder attribute so that checks for attributes can still know about the placement of `cfg` attributes. When we suggest removing items with `cfg_attr`s (fix Issue 56328) and make them verbose. We tweak the wording of the existing "unused `extern crate`" lint.

```
warning: unused extern crate
  --&gt; $DIR/removing-extern-crate.rs:9:1
   |
LL | extern crate removing_extern_crate as foo;
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unused
   |
note: the lint level is defined here
  --&gt; $DIR/removing-extern-crate.rs:6:9
   |
LL | #![warn(rust_2018_idioms)]
   |         ^^^^^^^^^^^^^^^^
   = note: `#[warn(unused_extern_crates)]` implied by `#[warn(rust_2018_idioms)]`
help: remove the unused `extern crate`
   |
LL - #[cfg_attr(test, macro_use)]
LL - extern crate removing_extern_crate as foo;
LL +
   |
```
diff --git a/compiler/rustc_lint/messages.ftl b/compiler/rustc_lint/messages.ftl
@@ -953,7 +953,8 @@ lint_unused_doc_comment = unused doc comment
     .help = to document an item produced by a macro, the macro must produce the documentation as part of its expansion
 
 lint_unused_extern_crate = unused extern crate
-    .suggestion = remove it
+    .label = unused
+    .suggestion = remove the unused `extern crate`
 
 lint_unused_import_braces = braces around {$node} is unnecessary
 
diff --git a/compiler/rustc_lint/src/early/diagnostics.rs b/compiler/rustc_lint/src/early/diagnostics.rs
@@ -292,8 +292,8 @@ pub(super) fn decorate_lint(
         BuiltinLintDiag::ByteSliceInPackedStructWithDerive { ty } => {
             lints::ByteSliceInPackedStructWithDerive { ty }.decorate_lint(diag);
         }
-        BuiltinLintDiag::UnusedExternCrate { removal_span } => {
-            lints::UnusedExternCrate { removal_span }.decorate_lint(diag);
+        BuiltinLintDiag::UnusedExternCrate { span, removal_span } => {
+            lints::UnusedExternCrate { span, removal_span }.decorate_lint(diag);
         }
         BuiltinLintDiag::ExternCrateNotIdiomatic { vis_span, ident_span } => {
             let suggestion_span = vis_span.between(ident_span);
diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
@@ -3051,7 +3051,9 @@ pub(crate) struct ByteSliceInPackedStructWithDerive {
 #[derive(LintDiagnostic)]
 #[diag(lint_unused_extern_crate)]
 pub(crate) struct UnusedExternCrate {
-    #[suggestion(code = "", applicability = "machine-applicable")]
+    #[label]
+    pub span: Span,
+    #[suggestion(code = "", applicability = "machine-applicable", style = "verbose")]
     pub removal_span: Span,
 }
 
diff --git a/compiler/rustc_lint_defs/src/lib.rs b/compiler/rustc_lint_defs/src/lib.rs
@@ -736,6 +736,7 @@ pub enum BuiltinLintDiag {
         ty: String,
     },
     UnusedExternCrate {
+        span: Span,
         removal_span: Span,
     },
     ExternCrateNotIdiomatic {
diff --git a/compiler/rustc_resolve/src/check_unused.rs b/compiler/rustc_resolve/src/check_unused.rs
@@ -154,6 +154,7 @@ impl<'a, 'ra, 'tcx> UnusedImportCheckVisitor<'a, 'ra, 'tcx> {
                         extern_crate.id,
                         span,
                         BuiltinLintDiag::UnusedExternCrate {
+                            span: extern_crate.span,
                             removal_span: extern_crate.span_with_attributes,
                         },
                     );
diff --git a/tests/ui/editions/edition-extern-crate-allowed.stderr b/tests/ui/editions/edition-extern-crate-allowed.stderr
@@ -2,14 +2,18 @@ warning: unused extern crate
   --> $DIR/edition-extern-crate-allowed.rs:7:1
    |
 LL | extern crate edition_extern_crate_allowed;
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove it
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unused
    |
 note: the lint level is defined here
   --> $DIR/edition-extern-crate-allowed.rs:5:9
    |
 LL | #![warn(rust_2018_idioms)]
    |         ^^^^^^^^^^^^^^^^
    = note: `#[warn(unused_extern_crates)]` implied by `#[warn(rust_2018_idioms)]`
+help: remove the unused `extern crate`
+   |
+LL - extern crate edition_extern_crate_allowed;
+   |
 
 warning: 1 warning emitted
 
diff --git a/tests/ui/imports/extern-crate-used.stderr b/tests/ui/imports/extern-crate-used.stderr
@@ -2,13 +2,18 @@ error: unused extern crate
   --> $DIR/extern-crate-used.rs:18:1
    |
 LL | extern crate core;
-   | ^^^^^^^^^^^^^^^^^^ help: remove it
+   | ^^^^^^^^^^^^^^^^^^ unused
    |
 note: the lint level is defined here
   --> $DIR/extern-crate-used.rs:6:9
    |
 LL | #![deny(unused_extern_crates)]
    |         ^^^^^^^^^^^^^^^^^^^^
+help: remove the unused `extern crate`
+   |
+LL - extern crate core;
+LL +
+   |
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/lint/unnecessary-extern-crate.stderr b/tests/ui/lint/unnecessary-extern-crate.stderr
@@ -2,43 +2,72 @@ error: unused extern crate
   --> $DIR/unnecessary-extern-crate.rs:6:1
    |
 LL | extern crate core;
-   | ^^^^^^^^^^^^^^^^^^ help: remove it
+   | ^^^^^^^^^^^^^^^^^^ unused
    |
 note: the lint level is defined here
   --> $DIR/unnecessary-extern-crate.rs:3:9
    |
 LL | #![deny(unused_extern_crates)]
    |         ^^^^^^^^^^^^^^^^^^^^
+help: remove the unused `extern crate`
+   |
+LL - extern crate core;
+   |
 
 error: unused extern crate
   --> $DIR/unnecessary-extern-crate.rs:9:1
    |
 LL | extern crate core as x;
-   | ^^^^^^^^^^^^^^^^^^^^^^^ help: remove it
+   | ^^^^^^^^^^^^^^^^^^^^^^^ unused
+   |
+help: remove the unused `extern crate`
+   |
+LL - extern crate core as x;
+   |
 
 error: unused extern crate
   --> $DIR/unnecessary-extern-crate.rs:31:5
    |
 LL |     extern crate core;
-   |     ^^^^^^^^^^^^^^^^^^ help: remove it
+   |     ^^^^^^^^^^^^^^^^^^ unused
+   |
+help: remove the unused `extern crate`
+   |
+LL -     extern crate core;
+   |
 
 error: unused extern crate
   --> $DIR/unnecessary-extern-crate.rs:35:5
    |
 LL |     extern crate core as x;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^ help: remove it
+   |     ^^^^^^^^^^^^^^^^^^^^^^^ unused
+   |
+help: remove the unused `extern crate`
+   |
+LL -     extern crate core as x;
+   |
 
 error: unused extern crate
   --> $DIR/unnecessary-extern-crate.rs:44:9
    |
 LL |         extern crate core;
-   |         ^^^^^^^^^^^^^^^^^^ help: remove it
+   |         ^^^^^^^^^^^^^^^^^^ unused
+   |
+help: remove the unused `extern crate`
+   |
+LL -         extern crate core;
+   |
 
 error: unused extern crate
   --> $DIR/unnecessary-extern-crate.rs:48:9
    |
 LL |         extern crate core as x;
-   |         ^^^^^^^^^^^^^^^^^^^^^^^ help: remove it
+   |         ^^^^^^^^^^^^^^^^^^^^^^^ unused
+   |
+help: remove the unused `extern crate`
+   |
+LL -         extern crate core as x;
+   |
 
 error: aborting due to 6 previous errors
 
diff --git a/tests/ui/lint/unused/lint-unused-extern-crate.stderr b/tests/ui/lint/unused/lint-unused-extern-crate.stderr
@@ -2,19 +2,30 @@ error: unused extern crate
   --> $DIR/lint-unused-extern-crate.rs:11:1
    |
 LL | extern crate lint_unused_extern_crate5;
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove it
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unused
    |
 note: the lint level is defined here
   --> $DIR/lint-unused-extern-crate.rs:7:9
    |
 LL | #![deny(unused_extern_crates)]
    |         ^^^^^^^^^^^^^^^^^^^^
+help: remove the unused `extern crate`
+   |
+LL - extern crate lint_unused_extern_crate5;
+LL +
+   |
 
 error: unused extern crate
   --> $DIR/lint-unused-extern-crate.rs:29:5
    |
 LL |     extern crate lint_unused_extern_crate2;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove it
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unused
+   |
+help: remove the unused `extern crate`
+   |
+LL -     extern crate lint_unused_extern_crate2;
+LL +
+   |
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/proc-macro/no-macro-use-attr.stderr b/tests/ui/proc-macro/no-macro-use-attr.stderr
@@ -2,13 +2,17 @@ warning: unused extern crate
   --> $DIR/no-macro-use-attr.rs:6:1
    |
 LL | extern crate test_macros;
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove it
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^ unused
    |
 note: the lint level is defined here
   --> $DIR/no-macro-use-attr.rs:4:9
    |
 LL | #![warn(unused_extern_crates)]
    |         ^^^^^^^^^^^^^^^^^^^^
+help: remove the unused `extern crate`
+   |
+LL - extern crate test_macros;
+   |
 
 warning: 1 warning emitted
 
diff --git a/tests/ui/rust-2018/extern-crate-idiomatic-in-2018.stderr b/tests/ui/rust-2018/extern-crate-idiomatic-in-2018.stderr
@@ -2,14 +2,18 @@ error: unused extern crate
   --> $DIR/extern-crate-idiomatic-in-2018.rs:12:1
    |
 LL | extern crate edition_lint_paths;
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove it
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unused
    |
 note: the lint level is defined here
   --> $DIR/extern-crate-idiomatic-in-2018.rs:9:9
    |
 LL | #![deny(rust_2018_idioms)]
    |         ^^^^^^^^^^^^^^^^
    = note: `#[deny(unused_extern_crates)]` implied by `#[deny(rust_2018_idioms)]`
+help: remove the unused `extern crate`
+   |
+LL - extern crate edition_lint_paths;
+   |
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/rust-2018/issue-54400-unused-extern-crate-attr-span.rs b/tests/ui/rust-2018/issue-54400-unused-extern-crate-attr-span.rs
@@ -8,7 +8,7 @@
 
 // The suggestion span should include the attribute.
 
-#[cfg(not(FALSE))] //~ HELP remove it
+#[cfg(not(FALSE))] //~ HELP remove
 extern crate edition_lint_paths;
 //~^ ERROR unused extern crate
 
diff --git a/tests/ui/rust-2018/issue-54400-unused-extern-crate-attr-span.stderr b/tests/ui/rust-2018/issue-54400-unused-extern-crate-attr-span.stderr
@@ -1,18 +1,20 @@
 error: unused extern crate
   --> $DIR/issue-54400-unused-extern-crate-attr-span.rs:12:1
    |
-LL | / #[cfg(not(FALSE))]
-LL | | extern crate edition_lint_paths;
-   | | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^-
-   | |________________________________|
-   |                                  help: remove it
+LL | extern crate edition_lint_paths;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unused
    |
 note: the lint level is defined here
   --> $DIR/issue-54400-unused-extern-crate-attr-span.rs:6:9
    |
 LL | #![deny(rust_2018_idioms)]
    |         ^^^^^^^^^^^^^^^^
    = note: `#[deny(unused_extern_crates)]` implied by `#[deny(rust_2018_idioms)]`
+help: remove the unused `extern crate`
+   |
+LL - #[cfg(not(FALSE))]
+LL - extern crate edition_lint_paths;
+   |
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/rust-2018/remove-extern-crate.stderr b/tests/ui/rust-2018/remove-extern-crate.stderr
@@ -2,14 +2,19 @@ warning: unused extern crate
   --> $DIR/remove-extern-crate.rs:11:1
    |
 LL | extern crate core;
-   | ^^^^^^^^^^^^^^^^^^ help: remove it
+   | ^^^^^^^^^^^^^^^^^^ unused
    |
 note: the lint level is defined here
   --> $DIR/remove-extern-crate.rs:7:9
    |
 LL | #![warn(rust_2018_idioms)]
    |         ^^^^^^^^^^^^^^^^
    = note: `#[warn(unused_extern_crates)]` implied by `#[warn(rust_2018_idioms)]`
+help: remove the unused `extern crate`
+   |
+LL - extern crate core;
+LL +
+   |
 
 warning: `extern crate` is not idiomatic in the new edition
   --> $DIR/remove-extern-crate.rs:35:5
diff --git a/tests/ui/rust-2018/removing-extern-crate-malformed-cfg.fixed b/tests/ui/rust-2018/removing-extern-crate-malformed-cfg.fixed
@@ -0,0 +1,15 @@
+//@ edition:2018
+//@ aux-build:../removing-extern-crate.rs
+//@ run-rustfix
+
+#![warn(rust_2018_idioms)]
+
+ //~ WARNING unused extern crate
+ //~ WARNING unused extern crate
+
+mod another {
+     //~ WARNING unused extern crate
+     //~ WARNING unused extern crate
+}
+
+fn main() {}
diff --git a/tests/ui/rust-2018/removing-extern-crate-malformed-cfg.rs b/tests/ui/rust-2018/removing-extern-crate-malformed-cfg.rs
@@ -0,0 +1,17 @@
+//@ edition:2018
+//@ aux-build:../removing-extern-crate.rs
+//@ run-rustfix
+
+#![warn(rust_2018_idioms)]
+
+#[cfg_attr(test, "macro_use")] //~ ERROR expected
+extern crate removing_extern_crate as foo; //~ WARNING unused extern crate
+extern crate core; //~ WARNING unused extern crate
+
+mod another {
+    #[cfg_attr(test)] //~ ERROR expected
+    extern crate removing_extern_crate as foo; //~ WARNING unused extern crate
+    extern crate core; //~ WARNING unused extern crate
+}
+
+fn main() {}
diff --git a/tests/ui/rust-2018/removing-extern-crate-malformed-cfg.stderr b/tests/ui/rust-2018/removing-extern-crate-malformed-cfg.stderr
diff --git a/tests/ui/rust-2018/removing-extern-crate.stderr b/tests/ui/rust-2018/removing-extern-crate.stderr

Original file line number	Diff line number	Diff line change
`@@ -292,8 +292,8 @@ pub(super) fn decorate_lint(`
`292`	`292`	`BuiltinLintDiag::ByteSliceInPackedStructWithDerive { ty } => {`
`293`	`293`	`lints::ByteSliceInPackedStructWithDerive { ty }.decorate_lint(diag);`
`294`	`294`	`}`
`295`		`- BuiltinLintDiag::UnusedExternCrate { removal_span } => {`
`296`		`- lints::UnusedExternCrate { removal_span }.decorate_lint(diag);`
	`295`	`+ BuiltinLintDiag::UnusedExternCrate { span, removal_span } => {`
	`296`	`+ lints::UnusedExternCrate { span, removal_span }.decorate_lint(diag);`
`297`	`297`	`}`
`298`	`298`	`BuiltinLintDiag::ExternCrateNotIdiomatic { vis_span, ident_span } => {`
`299`	`299`	`let suggestion_span = vis_span.between(ident_span);`
Original file line number	Diff line number	Diff line change
`@@ -2,14 +2,18 @@ warning: unused extern crate`
`2`	`2`	`--> $DIR/edition-extern-crate-allowed.rs:7:1`
`3`	`3`	`\|`
`4`	`4`	`LL \| extern crate edition_extern_crate_allowed;`
`5`		`- \| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove it`
	`5`	`+ \| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unused`
`6`	`6`	`\|`
`7`	`7`	`note: the lint level is defined here`
`8`	`8`	`--> $DIR/edition-extern-crate-allowed.rs:5:9`
`9`	`9`	`\|`
`10`	`10`	`LL \| #![warn(rust_2018_idioms)]`
`11`	`11`	`\| ^^^^^^^^^^^^^^^^`
`12`	`12`	= note: `#[warn(unused_extern_crates)]` implied by `#[warn(rust_2018_idioms)]`
	`13`	+help: remove the unused `extern crate`
	`14`	`+ \|`
	`15`	`+LL - extern crate edition_extern_crate_allowed;`
	`16`	`+ \|`
`13`	`17`
`14`	`18`	`warning: 1 warning emitted`
`15`	`19`
Original file line number	Diff line number	Diff line change
`@@ -2,13 +2,18 @@ error: unused extern crate`
`2`	`2`	`--> $DIR/extern-crate-used.rs:18:1`
`3`	`3`	`\|`
`4`	`4`	`LL \| extern crate core;`
`5`		`- \| ^^^^^^^^^^^^^^^^^^ help: remove it`
	`5`	`+ \| ^^^^^^^^^^^^^^^^^^ unused`
`6`	`6`	`\|`
`7`	`7`	`note: the lint level is defined here`
`8`	`8`	`--> $DIR/extern-crate-used.rs:6:9`
`9`	`9`	`\|`
`10`	`10`	`LL \| #![deny(unused_extern_crates)]`
`11`	`11`	`\| ^^^^^^^^^^^^^^^^^^^^`
	`12`	+help: remove the unused `extern crate`
	`13`	`+ \|`
	`14`	`+LL - extern crate core;`
	`15`	`+LL +`
	`16`	`+ \|`
`12`	`17`
`13`	`18`	`error: aborting due to 1 previous error`
`14`	`19`
Original file line number	Diff line number	Diff line change
`@@ -2,13 +2,17 @@ warning: unused extern crate`
`2`	`2`	`--> $DIR/no-macro-use-attr.rs:6:1`
`3`	`3`	`\|`
`4`	`4`	`LL \| extern crate test_macros;`
`5`		`- \| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove it`
	`5`	`+ \| ^^^^^^^^^^^^^^^^^^^^^^^^^ unused`
`6`	`6`	`\|`
`7`	`7`	`note: the lint level is defined here`
`8`	`8`	`--> $DIR/no-macro-use-attr.rs:4:9`
`9`	`9`	`\|`
`10`	`10`	`LL \| #![warn(unused_extern_crates)]`
`11`	`11`	`\| ^^^^^^^^^^^^^^^^^^^^`
	`12`	+help: remove the unused `extern crate`
	`13`	`+ \|`
	`14`	`+LL - extern crate test_macros;`
	`15`	`+ \|`
`12`	`16`
`13`	`17`	`warning: 1 warning emitted`
`14`	`18`