Fix removal span calculation of unused_qualifications suggestion

Author: jieyouxu

compiler/rustc_lint/src/context.rs

@@ -956,11 +956,11 @@ pub trait LintContext: Sized {
                     db.span_note(glob_reexport_span, format!("the name `{}` in the {} namespace is supposed to be publicly re-exported here", name, namespace));
                     db.span_note(private_item_span, "but the private item here shadows it".to_owned());
                 }
-                BuiltinLintDiagnostics::UnusedQualifications { path_span, unqualified_path } => {
+                BuiltinLintDiagnostics::UnusedQualifications { removal_span } => {
                     db.span_suggestion_verbose(
-                        path_span,
-                        "replace it with the unqualified path",
-                        unqualified_path,
+                        removal_span,
+                        "remove the unnecessary path segments",
+                        "",
                         Applicability::MachineApplicable
                     );
                 }

compiler/rustc_lint_defs/src/lib.rs

@@ -551,10 +551,8 @@ pub enum BuiltinLintDiagnostics {
         private_item_span: Span,
     },
     UnusedQualifications {
-        /// The span of the unnecessarily-qualified path.
-        path_span: Span,
-        /// The replacement unqualified path.
-        unqualified_path: Ident,
+        /// The span of the unnecessarily-qualified path to remove.
+        removal_span: Span,
     },
 }
 

compiler/rustc_resolve/src/late.rs

@@ -3911,8 +3911,9 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
             && path[0].ident.name != kw::PathRoot
             && path[0].ident.name != kw::DollarCrate
         {
+            let last_segment = *path.last().unwrap();
             let unqualified_result = {
-                match self.resolve_path(&[*path.last().unwrap()], Some(ns), None) {
+                match self.resolve_path(&[last_segment], Some(ns), None) {
                     PathResult::NonModule(path_res) => path_res.expect_full_res(),
                     PathResult::Module(ModuleOrUniformRoot::Module(module)) => {
                         module.res().unwrap()
@@ -3928,8 +3929,7 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                     finalize.path_span,
                     "unnecessary qualification",
                     lint::BuiltinLintDiagnostics::UnusedQualifications {
-                        path_span: finalize.path_span,
-                        unqualified_path: path.last().unwrap().ident
+                        removal_span: finalize.path_span.until(last_segment.ident.span),
                     }
                 )
             }

tests/ui/lint/lint-qualification.fixed

@@ -0,0 +1,21 @@
+// run-rustfix
+#![deny(unused_qualifications)]
+#![allow(deprecated)]
+
+mod foo {
+    pub fn bar() {}
+}
+
+fn main() {
+    use foo::bar;
+    bar(); //~ ERROR: unnecessary qualification
+    bar();
+
+    let _ = || -> Result<(), ()> { try!(Ok(())); Ok(()) }; // issue #37345
+
+    macro_rules! m { () => {
+        $crate::foo::bar(); // issue #37357
+        ::foo::bar(); // issue #38682
+    } }
+    m!();
+}

tests/ui/lint/lint-qualification.rs

@@ -1,3 +1,4 @@
+// run-rustfix
 #![deny(unused_qualifications)]
 #![allow(deprecated)]
 

tests/ui/lint/lint-qualification.stderr

@@ -1,18 +1,19 @@
 error: unnecessary qualification
-  --> $DIR/lint-qualification.rs:10:5
+  --> $DIR/lint-qualification.rs:11:5
    |
 LL |     foo::bar();
    |     ^^^^^^^^
    |
 note: the lint level is defined here
-  --> $DIR/lint-qualification.rs:1:9
+  --> $DIR/lint-qualification.rs:2:9
    |
 LL | #![deny(unused_qualifications)]
    |         ^^^^^^^^^^^^^^^^^^^^^
-help: replace it with the unqualified path
+help: remove the unnecessary path segments
+   |
+LL -     foo::bar();
+LL +     bar();
    |
-LL |     bar();
-   |     ~~~
 
 error: aborting due to previous error
 

tests/ui/resolve/issue-113808-invalid-unused-qualifications-suggestion.fixed

@@ -0,0 +1,31 @@
+// run-rustfix
+
+#![deny(unused_qualifications)]
+#![feature(unsized_fn_params)]
+
+#[allow(unused_imports)]
+use std::ops;
+use std::ops::Index;
+
+pub struct A;
+
+impl Index<str> for A {
+    //~^ ERROR unnecessary qualification
+    type Output = ();
+    fn index(&self, _: str) -> &Self::Output {
+        &()
+    }
+}
+
+mod inner {
+    pub trait Trait<T> {}
+}
+
+// the import needs to be here for the lint to show up
+#[allow(unused_imports)]
+use inner::Trait;
+
+impl Trait<u8> for () {}
+//~^ ERROR unnecessary qualification
+
+fn main() {}

tests/ui/resolve/issue-113808-invalid-unused-qualifications-suggestion.rs

@@ -0,0 +1,31 @@
+// run-rustfix
+
+#![deny(unused_qualifications)]
+#![feature(unsized_fn_params)]
+
+#[allow(unused_imports)]
+use std::ops;
+use std::ops::Index;
+
+pub struct A;
+
+impl ops::Index<str> for A {
+    //~^ ERROR unnecessary qualification
+    type Output = ();
+    fn index(&self, _: str) -> &Self::Output {
+        &()
+    }
+}
+
+mod inner {
+    pub trait Trait<T> {}
+}
+
+// the import needs to be here for the lint to show up
+#[allow(unused_imports)]
+use inner::Trait;
+
+impl inner::Trait<u8> for () {}
+//~^ ERROR unnecessary qualification
+
+fn main() {}

tests/ui/resolve/issue-113808-invalid-unused-qualifications-suggestion.stderr

@@ -0,0 +1,31 @@
+error: unnecessary qualification
+  --> $DIR/issue-113808-invalid-unused-qualifications-suggestion.rs:12:6
+   |
+LL | impl ops::Index<str> for A {
+   |      ^^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/issue-113808-invalid-unused-qualifications-suggestion.rs:3:9
+   |
+LL | #![deny(unused_qualifications)]
+   |         ^^^^^^^^^^^^^^^^^^^^^
+help: remove the unnecessary path segments
+   |
+LL - impl ops::Index<str> for A {
+LL + impl Index<str> for A {
+   |
+
+error: unnecessary qualification
+  --> $DIR/issue-113808-invalid-unused-qualifications-suggestion.rs:28:6
+   |
+LL | impl inner::Trait<u8> for () {}
+   |      ^^^^^^^^^^^^^^^^
+   |
+help: remove the unnecessary path segments
+   |
+LL - impl inner::Trait<u8> for () {}
+LL + impl Trait<u8> for () {}
+   |
+
+error: aborting due to 2 previous errors
+

tests/ui/resolve/unused-qualifications-suggestion.stderr

@@ -9,21 +9,23 @@ note: the lint level is defined here
    |
 LL | #![deny(unused_qualifications)]
    |         ^^^^^^^^^^^^^^^^^^^^^
-help: replace it with the unqualified path
+help: remove the unnecessary path segments
+   |
+LL -     foo::bar();
+LL +     bar();
    |
-LL |     bar();
-   |     ~~~
 
 error: unnecessary qualification
   --> $DIR/unused-qualifications-suggestion.rs:21:5
    |
 LL |     baz::qux::quux();
    |     ^^^^^^^^^^^^^^
    |
-help: replace it with the unqualified path
+help: remove the unnecessary path segments
+   |
+LL -     baz::qux::quux();
+LL +     quux();
    |
-LL |     quux();
-   |     ~~~~
 
 error: aborting due to 2 previous errors