[clang] 4e1c487 - [clang] Fix crash when creating deduction guide.

[Adam Czachorowski via cfe-commits]

Author: Adam Czachorowski
Date: 2021-03-09T16:57:56+01:00
New Revision: 4e1c487004a29ec9bc56fd47fc30336d033c57dd

URL: https://github.com/llvm/llvm-project/commit/4e1c487004a29ec9bc56fd47fc30336d033c57dd
DIFF: https://github.com/llvm/llvm-project/commit/4e1c487004a29ec9bc56fd47fc30336d033c57dd.diff

LOG: [clang] Fix crash when creating deduction guide.

We used to trigger assertion when transforming c-tor with unparsed
default argument. Now we ignore such constructors for this purpose.

Differential Revision: https://reviews.llvm.org/D97965

Added: 
    

Modified: 
    clang/lib/Sema/SemaTemplate.cpp
    clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 12880b95b9c6..7a65c2a6fe2c 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -2494,6 +2494,12 @@ void Sema::DeclareImplicitDeductionGuides(TemplateDecl *Template,
     if (!CD || (!FTD && CD->isFunctionTemplateSpecialization()))
       continue;
 
+    // Cannot make a deduction guide when unparsed arguments are present.
+    if (std::any_of(CD->param_begin(), CD->param_end(), [](ParmVarDecl *P) {
+          return !P || P->hasUnparsedDefaultArg();
+        }))
+      continue;
+
     Transform.transformConstructor(FTD, CD);
     AddedAny = true;
   }

diff  --git a/clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp b/clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
index 305cc3e976b0..161944f9e64f 100644
--- a/clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
+++ b/clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp
@@ -416,6 +416,17 @@ B b(0, {});
 
 }
 
+namespace no_crash_on_default_arg {
+class A {
+  template <typename T> class B {
+    B(int c = 1);
+  };
+  // This used to crash due to unparsed default arg above. The diagnostic could
+  // be improved, but the point of this test is to simply check we do not crash.
+  B(); // expected-error {{deduction guide declaration without trailing return type}}
+};
+} // namespace no_crash_on_default_arg
+
 #pragma clang diagnostic push
 #pragma clang diagnostic warning "-Wctad-maybe-unsupported"
 namespace test_implicit_ctad_warning {