From 7f05fe1aeeb005b552c6a3093b61659e7b578b14 Mon Sep 17 00:00:00 2001
From: Haojian Wu <hokein.wu@gmail.com>
Date: Mon, 5 Oct 2020 12:52:03 +0200
Subject: [PATCH] [AST][RecoveryExpr] Fix a crash on undeduced type.

We should not capture the type if the function return type is undeduced.

Reviewed By: adamcz

Differential Revision: https://reviews.llvm.org/D87350
---
 clang/lib/Sema/SemaOverload.cpp           | 7 ++++++-
 clang/test/AST/ast-dump-recovery.cpp      | 6 ++++++
 clang/test/SemaCXX/recovery-expr-type.cpp | 6 ++++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 0c252a4..4696ed5 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -12880,7 +12880,12 @@ static QualType chooseRecoveryType(OverloadCandidateSet &CS,
     for (const auto &C : CS)
       ConsiderCandidate(C);
 
-  return Result.getValueOr(QualType());
+  if (!Result)
+    return QualType();
+  auto Value = Result.getValue();
+  if (Value.isNull() || Value->isUndeducedType())
+    return QualType();
+  return Value;
 }
 
 /// FinishOverloadedCallExpr - given an OverloadCandidateSet, builds and returns
diff --git a/clang/test/AST/ast-dump-recovery.cpp b/clang/test/AST/ast-dump-recovery.cpp
index fd7c923..69d5f80 100644
--- a/clang/test/AST/ast-dump-recovery.cpp
+++ b/clang/test/AST/ast-dump-recovery.cpp
@@ -126,6 +126,12 @@ void test(int x) {
 // CHECK-NEXT:|   `-UnresolvedLookupExpr {{.*}} 'invalid'
 struct alignas(invalid()) Aligned {};
 
+auto f();
+int f(double);
+// CHECK:      VarDecl {{.*}} unknown_type_call 'int'
+// CHECK-NEXT: `-RecoveryExpr {{.*}} '<dependent type>'
+int unknown_type_call = f(0, 0);
+
 void InvalidInitalizer(int x) {
   struct Bar { Bar(); };
   // CHECK:     `-VarDecl {{.*}} a1 'Bar'
diff --git a/clang/test/SemaCXX/recovery-expr-type.cpp b/clang/test/SemaCXX/recovery-expr-type.cpp
index 075d014..8186a81 100644
--- a/clang/test/SemaCXX/recovery-expr-type.cpp
+++ b/clang/test/SemaCXX/recovery-expr-type.cpp
@@ -105,3 +105,9 @@ typedef int arr[];
 int v = arr(); // expected-error {{array types cannot be value-initialized}} \
                   expected-error {{cannot initialize a variable of type 'int' with an rvalue of type 'test8::arr'}}
 }
+
+namespace test9 {
+auto f(); // expected-note {{candidate function not viable}}
+// verify no crash on evaluating the size of undeduced auto type.
+static_assert(sizeof(f(1)), ""); // expected-error {{no matching function for call to 'f'}}
+}
-- 
2.7.4