3 files changed, 23 insertions, 2 deletions
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index 5c1a7bb3cfd..c74b02877c9 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -799,7 +799,10 @@ SourceLocation Parser::ParseDecltypeSpecifier(DeclSpec &DS) {
       //   The operand of the decltype specifier is an unevaluated operand.
       EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated,
                                                    nullptr,/*IsDecltype=*/true);
-      Result = Actions.CorrectDelayedTyposInExpr(ParseExpression());
+      Result =
+          Actions.CorrectDelayedTyposInExpr(ParseExpression(), [](Expr *E) {
+            return E->hasPlaceholderType() ? ExprError() : E;
+          });
       if (Result.isInvalid()) {
         DS.SetTypeSpecError();
         if (SkipUntil(tok::r_paren, StopAtSemi | StopBeforeMatch)) {
diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
index 72af14d068f..315c9574e95 100644
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/clang/lib/Parse/ParseExpr.cpp
@@ -928,7 +928,8 @@ ExprResult Parser::ParseCastExpression(bool isUnaryExpression,
     Res = Actions.ActOnIdExpression(
         getCurScope(), ScopeSpec, TemplateKWLoc, Name, Tok.is(tok::l_paren),
         isAddressOfOperand, std::move(Validator),
-        /*IsInlineAsmIdentifier=*/false, &Replacement);
+        /*IsInlineAsmIdentifier=*/false,
+        Tok.is(tok::r_paren) ? nullptr : &Replacement);
     if (!Res.isInvalid() && !Res.get()) {
       UnconsumeToken(Replacement);
       return ParseCastExpression(isUnaryExpression, isAddressOfOperand,
diff --git a/clang/test/SemaCXX/typo-correction-cxx11.cpp b/clang/test/SemaCXX/typo-correction-cxx11.cpp
new file mode 100644
index 00000000000..573c6aa1171
--- /dev/null
+++ b/clang/test/SemaCXX/typo-correction-cxx11.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s
+
+namespace PR23186 {
+decltype(ned);  // expected-error-re {{use of undeclared identifier 'ned'{{$}}}}
+// The code below was triggering an UNREACHABLE in ASTContext::getTypeInfoImpl
+// once the above code failed to recover properly after making the bogus
+// correction of 'ned' to 'new'.
+template <typename>
+struct S {
+  enum { V };
+  void f() {
+    switch (0)
+    case V:
+      ;
+  }
+};
+}