Auto merge of #80686 - GuillaumeGomez:error-doc-alias-same-name, r=jyn514

Error when #[doc(alias)] has same name as the item

Something I came across when reviewing some doc alias PRs.

r? `@jyn514`

compiler/rustc_passes/src/check_attr.rs

@@ -310,7 +310,7 @@ fn check_doc_alias(&self, meta: &NestedMetaItem, hir_id: HirId, target: Target)
                 .sess
                 .struct_span_err(
                     meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
-                    &format!("{:?} character isn't allowed in `#[doc(alias = \"...\")]`", c,),
+                    &format!("{:?} character isn't allowed in `#[doc(alias = \"...\")]`", c),
                 )
                 .emit();
             return false;
@@ -358,6 +358,17 @@ fn check_doc_alias(&self, meta: &NestedMetaItem, hir_id: HirId, target: Target)
                 .emit();
             return false;
         }
+        let item_name = self.tcx.hir().name(hir_id);
+        if item_name.to_string() == doc_alias {
+            self.tcx
+                .sess
+                .struct_span_err(
+                    meta.span(),
+                    &format!("`#[doc(alias = \"...\")]` is the same as the item's name"),
+                )
+                .emit();
+            return false;
+        }
         true
     }
 

src/test/rustdoc-ui/doc-alias-same-name.rs

@@ -0,0 +1,4 @@
+#![crate_type = "lib"]
+
+#[doc(alias = "Foo")] //~ ERROR
+pub struct Foo;

src/test/rustdoc-ui/doc-alias-same-name.stderr

@@ -0,0 +1,8 @@
+error: `#[doc(alias = "...")]` is the same as the item's name
+  --> $DIR/doc-alias-same-name.rs:3:7
+   |
+LL | #[doc(alias = "Foo")]
+   |       ^^^^^^^^^^^^^
+
+error: aborting due to previous error
+

src/test/ui/doc-alias-same-name.rs

@@ -0,0 +1,4 @@
+#![crate_type = "lib"]
+
+#[doc(alias = "Foo")] //~ ERROR
+pub struct Foo;

src/test/ui/doc-alias-same-name.stderr

@@ -0,0 +1,8 @@
+error: `#[doc(alias = "...")]` is the same as the item's name
+  --> $DIR/doc-alias-same-name.rs:3:7
+   |
+LL | #[doc(alias = "Foo")]
+   |       ^^^^^^^^^^^^^
+
+error: aborting due to previous error
+