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Use cfg_attr AST placeholder AST cfg_attr_trace for diagnostics
Previously, when evaluating a `#[cfg_attr(..)]` to false, the entire attribute was removed from the AST. Afterwards in #138515, we insert in its place a placeholder attribute so that checks for attributes can still know about their placement. This is particularly relevant when we suggest removing items with `cfg_attr`s (fix #56328). We use the placeholder as it is an ident that can't be written by the end user to begin with. We tweak the wording of the existing "unused `extern crate`" lint. ``` warning: unused `extern crate` --> $DIR/removing-extern-crate.rs:9:1 | LL | extern crate removing_extern_crate as foo; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unused | note: the lint level is defined here --> $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 + | ```
1 parent 642e49b commit 5412241

30 files changed

+271
-71
lines changed

‎compiler/rustc_lint/messages.ftl‎

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -952,8 +952,9 @@ lint_unused_doc_comment = unused doc comment
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.label = rustdoc does not generate documentation for macro invocations
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.help = to document an item produced by a macro, the macro must produce the documentation as part of its expansion
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955-
lint_unused_extern_crate = unused extern crate
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.suggestion = remove it
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lint_unused_extern_crate = unused `extern crate`
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.label = unused
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.suggestion = remove the unused `extern crate`
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lint_unused_import_braces = braces around {$node} is unnecessary
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‎compiler/rustc_lint/src/early/diagnostics.rs‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -292,8 +292,8 @@ pub(super) fn decorate_lint(
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BuiltinLintDiag::ByteSliceInPackedStructWithDerive { ty } => {
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lints::ByteSliceInPackedStructWithDerive { ty }.decorate_lint(diag);
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}
295-
BuiltinLintDiag::UnusedExternCrate { removal_span } => {
296-
lints::UnusedExternCrate { removal_span }.decorate_lint(diag);
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BuiltinLintDiag::UnusedExternCrate { span, removal_span } => {
296+
lints::UnusedExternCrate { span, removal_span }.decorate_lint(diag);
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}
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BuiltinLintDiag::ExternCrateNotIdiomatic { vis_span, ident_span } => {
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let suggestion_span = vis_span.between(ident_span);

‎compiler/rustc_lint/src/lints.rs‎

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3051,7 +3051,9 @@ pub(crate) struct ByteSliceInPackedStructWithDerive {
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#[derive(LintDiagnostic)]
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#[diag(lint_unused_extern_crate)]
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pub(crate) struct UnusedExternCrate {
3054-
#[suggestion(code = "", applicability = "machine-applicable")]
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#[label]
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pub span: Span,
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#[suggestion(code = "", applicability = "machine-applicable", style = "verbose")]
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pub removal_span: Span,
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}
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‎compiler/rustc_lint_defs/src/lib.rs‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -736,6 +736,7 @@ pub enum BuiltinLintDiag {
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ty: String,
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},
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UnusedExternCrate {
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span: Span,
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removal_span: Span,
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},
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ExternCrateNotIdiomatic {

‎compiler/rustc_resolve/src/check_unused.rs‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -154,6 +154,7 @@ impl<'a, 'ra, 'tcx> UnusedImportCheckVisitor<'a, 'ra, 'tcx> {
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extern_crate.id,
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span,
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BuiltinLintDiag::UnusedExternCrate {
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span: extern_crate.span,
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removal_span: extern_crate.span_with_attributes,
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},
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);

‎tests/ui/editions/edition-extern-crate-allowed.rs‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -5,6 +5,6 @@
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#![warn(rust_2018_idioms)]
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extern crate edition_extern_crate_allowed;
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//~^ WARNING unused extern crate
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//~^ WARNING unused `extern crate`
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fn main() {}

‎tests/ui/editions/edition-extern-crate-allowed.stderr‎

Lines changed: 6 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,15 +1,19 @@
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warning: unused extern crate
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warning: unused `extern crate`
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--> $DIR/edition-extern-crate-allowed.rs:7:1
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|
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LL | extern crate edition_extern_crate_allowed;
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove it
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unused
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|
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note: the lint level is defined here
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--> $DIR/edition-extern-crate-allowed.rs:5:9
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|
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LL | #![warn(rust_2018_idioms)]
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| ^^^^^^^^^^^^^^^^
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= note: `#[warn(unused_extern_crates)]` implied by `#[warn(rust_2018_idioms)]`
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help: remove the unused `extern crate`
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|
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LL - extern crate edition_extern_crate_allowed;
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|
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warning: 1 warning emitted
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‎tests/ui/imports/extern-crate-used.rs‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -15,7 +15,7 @@ extern crate core as iso3;
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extern crate core as iso4;
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// Doesn't introduce its extern prelude entry, so it's still considered unused.
18-
extern crate core; //~ ERROR unused extern crate
18+
extern crate core; //~ ERROR unused `extern crate`
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mod m {
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use iso1::any as are_you_okay1;

‎tests/ui/imports/extern-crate-used.stderr‎

Lines changed: 7 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,14 +1,19 @@
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error: unused extern crate
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error: unused `extern crate`
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--> $DIR/extern-crate-used.rs:18:1
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|
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LL | extern crate core;
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| ^^^^^^^^^^^^^^^^^^ help: remove it
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| ^^^^^^^^^^^^^^^^^^ unused
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|
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note: the lint level is defined here
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--> $DIR/extern-crate-used.rs:6:9
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|
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LL | #![deny(unused_extern_crates)]
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| ^^^^^^^^^^^^^^^^^^^^
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help: remove the unused `extern crate`
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|
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LL - extern crate core;
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LL +
16+
|
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1318
error: aborting due to 1 previous error
1419

‎tests/ui/lint/unnecessary-extern-crate.rs‎

Lines changed: 6 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -4,10 +4,10 @@
44
#![feature(test)]
55

66
extern crate core;
7-
//~^ ERROR unused extern crate
7+
//~^ ERROR unused `extern crate`
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//~| HELP remove
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extern crate core as x;
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//~^ ERROR unused extern crate
10+
//~^ ERROR unused `extern crate`
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//~| HELP remove
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1313
extern crate proc_macro;
@@ -29,11 +29,11 @@ mod foo {
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pub(super) extern crate alloc as d;
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3131
extern crate core;
32-
//~^ ERROR unused extern crate
32+
//~^ ERROR unused `extern crate`
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//~| HELP remove
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extern crate core as x;
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//~^ ERROR unused extern crate
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//~^ ERROR unused `extern crate`
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//~| HELP remove
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pub extern crate test;
@@ -42,11 +42,11 @@ mod foo {
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4343
mod bar {
4444
extern crate core;
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//~^ ERROR unused extern crate
45+
//~^ ERROR unused `extern crate`
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//~| HELP remove
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4848
extern crate core as x;
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//~^ ERROR unused extern crate
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//~^ ERROR unused `extern crate`
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//~| HELP remove
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pub(in crate::foo::bar) extern crate alloc as e;

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