rustdoc: skip PatKind::Missing in visit_pat

Author: el-ev

compiler/rustc_ast_pretty/src/pprust/mod.rs

@@ -33,6 +33,9 @@ pub fn where_bound_predicate_to_string(where_bound_predicate: &ast::WhereBoundPr
     State::new().where_bound_predicate_to_string(where_bound_predicate)
 }
 
+/// # Panics
+///
+/// Panics if `pat.kind` is `PatKind::Missing`.
 pub fn pat_to_string(pat: &ast::Pat) -> String {
     State::new().pat_to_string(pat)
 }

src/librustdoc/html/macro_expansion.rs

@@ -1,5 +1,5 @@
 use rustc_ast::visit::{Visitor, walk_crate, walk_expr, walk_item, walk_pat, walk_stmt};
-use rustc_ast::{Crate, Expr, Item, Pat, Stmt};
+use rustc_ast::{Crate, Expr, Item, Pat, PatKind, Stmt};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_span::source_map::SourceMap;
 use rustc_span::{BytePos, Span};
@@ -147,7 +147,7 @@ impl<'ast> Visitor<'ast> for ExpandedCodeVisitor<'ast> {
     }
 
     fn visit_pat(&mut self, pat: &'ast Pat) {
-        if pat.span.from_expansion() {
+        if pat.span.from_expansion() && !matches!(pat.kind, PatKind::Missing) {
             self.handle_new_span(pat.span, || rustc_ast_pretty::pprust::pat_to_string(pat));
         } else {
             walk_pat(self, pat);

tests/rustdoc/macro-expansion/missing-par-ice-150154.rs

@@ -0,0 +1,18 @@
+// Ensure rustdoc does not ICE When expanding a macro that
+// generates a `PatKind::Missing` pattern.
+
+//@ compile-flags: -Zunstable-options --generate-macro-expansion
+
+#![crate_name = "foo"]
+
+//@ has 'src/foo/missing-par-ice-150154.rs.html'
+
+macro_rules! foo {
+    () => {
+        fn(())
+    }
+}
+
+fn bar() {
+    let _: foo!();
+}