Fix invalid "jump-to-def" doc link generation when an item has a derive proc-macro

src/librustdoc/html/span_map.rs

@@ -144,6 +144,10 @@ impl<'tcx> SpanMapVisitor<'tcx> {
                 let span = path.segments.last().map_or(path.span, |seg| seg.ident.span);
                 // In case the path ends with generics, we remove them from the span.
                 let span = if only_use_last_segment {
+                    if path.span.from_expansion() {
+                        // For now we don't handle span from macro expansions so nothing to do here.
+                        return;
+                    }
                     span
                 } else {
                     // In `use` statements, the included item is not in the path segments. However,

tests/rustdoc-html/jump-to-def/item-with-derive.rs

@@ -0,0 +1,21 @@
+// This test ensures that the item name will link to its item's page even if there
+// is a `#[derive(...)]`.
+// This is a regression test for <https://github.com/rust-lang/rust/issues/158050>.
+
+//@ compile-flags: -Zunstable-options --generate-link-to-definition
+
+#![crate_name = "foo"]
+
+//@ has 'src/foo/item-with-derive.rs.html'
+//@ has - '//a[@href="../../foo/struct.Bar.html"]' 'Bar'
+#[derive(Debug)]
+pub struct Bar {
+    x: u8,
+}
+
+// Same test with an enum just in case...
+//@ has - '//a[@href="../../foo/enum.Blob.html"]' 'Blob'
+#[derive(Debug)]
+pub enum Blob {
+    X,
+}