Reland: [clang] Use getDefaultArgRange instead of getDefaultArg to retrieve

source location in `ConvertConstructorToDeductionGuideTransform`.

The commit fec4716 was reverted by accident in 7415524.

Reland it with a testcase.

Author: hokein

clang/lib/Sema/SemaTemplate.cpp

@@ -2679,7 +2679,7 @@ struct ConvertConstructorToDeductionGuideTransform {
       // placeholder to indicate there is a default argument.
       QualType ParamTy = NewDI->getType();
       NewDefArg = new (SemaRef.Context)
-          OpaqueValueExpr(OldParam->getDefaultArg()->getBeginLoc(),
+          OpaqueValueExpr(OldParam->getDefaultArgRange().getBegin(),
                           ParamTy.getNonLValueExprType(SemaRef.Context),
                           ParamTy->isLValueReferenceType()   ? VK_LValue
                           : ParamTy->isRValueReferenceType() ? VK_XValue

clang/test/SemaTemplate/ctad.cpp

@@ -54,3 +54,18 @@ template<class T, class B> struct Y { Y(T); };
 template<class T, class B=void> struct Y ;
 Y y(1);
 }
+
+namespace NoCrashOnGettingDefaultArgLoc {
+template <typename>
+class A {
+  A(int = 1); // expected-note {{candidate template ignored: couldn't infer template argumen}}
+};
+class C : A<int> {
+  using A::A;
+};
+template <typename>
+class D : C { // expected-note {{candidate function template not viable: requires 1 argument}}
+  using C::C;
+};
+D abc; // expected-error {{no viable constructor or deduction guide}}
+}