Don't trigger unused_trait_names in macros (#14947)

Closes #14924

changelog: [`unused_trait_names`] no longer triggers in macros

Author: flip1995

clippy_lints/src/unused_trait_names.rs

@@ -6,7 +6,7 @@ use clippy_utils::source::snippet_opt;
 use rustc_errors::Applicability;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::{Item, ItemKind, UseKind};
-use rustc_lint::{LateContext, LateLintPass, LintContext as _};
+use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::Visibility;
 use rustc_session::impl_lint_pass;
 use rustc_span::symbol::kw;
@@ -59,7 +59,7 @@ impl_lint_pass!(UnusedTraitNames => [UNUSED_TRAIT_NAMES]);
 
 impl<'tcx> LateLintPass<'tcx> for UnusedTraitNames {
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'tcx>) {
-        if !item.span.in_external_macro(cx.sess().source_map())
+        if !item.span.from_expansion()
             && let ItemKind::Use(path, UseKind::Single(ident)) = item.kind
             // Ignore imports that already use Underscore
             && ident.name != kw::Underscore

tests/ui/unused_trait_names.fixed

@@ -200,11 +200,11 @@ fn msrv_1_33() {
     MyStruct.do_things();
 }
 
+// Linting inside macro expansion is no longer supported
 mod lint_inside_macro_expansion_bad {
     macro_rules! foo {
         () => {
-            use std::any::Any as _;
-            //~^ unused_trait_names
+            use std::any::Any;
             fn bar() {
                 "bar".type_id();
             }

tests/ui/unused_trait_names.rs

@@ -200,11 +200,11 @@ fn msrv_1_33() {
     MyStruct.do_things();
 }
 
+// Linting inside macro expansion is no longer supported
 mod lint_inside_macro_expansion_bad {
     macro_rules! foo {
         () => {
             use std::any::Any;
-            //~^ unused_trait_names
             fn bar() {
                 "bar".type_id();
             }

tests/ui/unused_trait_names.stderr

@@ -58,16 +58,5 @@ error: importing trait that is only used anonymously
 LL |     use simple_trait::{MyStruct, MyTrait};
    |                                  ^^^^^^^ help: use: `MyTrait as _`
 
-error: importing trait that is only used anonymously
-  --> tests/ui/unused_trait_names.rs:206:27
-   |
-LL |             use std::any::Any;
-   |                           ^^^ help: use: `Any as _`
-...
-LL |     foo!();
-   |     ------ in this macro invocation
-   |
-   = note: this error originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error: aborting due to 10 previous errors
+error: aborting due to 9 previous errors