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Improve template argument deduction in the case where the parameter 

type is a template-id (e.g., basic_ostream<CharT, Traits>) and the
argument type is a class that has a derived class matching the
parameter type. Previously, we were giving up on template argument
deduction too early.

llvm-svn: 83177
This commit is contained in:
Douglas Gregor 2009-09-30 22:13:51 +00:00
parent b633d7a665
commit 42909754f6
2 changed files with 4 additions and 8 deletions
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8
clang/lib/Sema/SemaTemplateDeduction.cpp
View File

@ -651,8 +651,7 @@ DeduceTemplateArguments(ASTContext &Context,
= DeduceTemplateArguments(Context, TemplateParams, SpecParam, Arg,
Info, Deduced);
if (Result && (TDF & TDF_DerivedClass) &&
Result != Sema::TDK_Inconsistent) {
if (Result && (TDF & TDF_DerivedClass)) {
// C++ [temp.deduct.call]p3b3:
// If P is a class, and P has the form template-id, then A can be a
// derived class of the deduced A. Likewise, if P is a pointer to a
@ -690,11 +689,6 @@ DeduceTemplateArguments(ASTContext &Context,
// note that we had some success.
if (BaseResult == Sema::TDK_Success)
Successful = true;
// If deduction against this base resulted in an inconsistent
// set of deduced template arguments, template argument
// deduction fails.
else if (BaseResult == Sema::TDK_Inconsistent)
return BaseResult;
}
// Visit base classes

4
clang/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.call/p3.cpp
View File

@ -66,6 +66,7 @@ template<typename T, int I> struct C { };
struct D : public C<int, 1> { };
struct E : public D { };
struct F : A<float> { };
struct G : A<float>, C<int, 1> { };
template<typename T, int I>
C<T, I> *f4a(const C<T, I>&);
@ -75,12 +76,13 @@ template<typename T, int I>
C<T, I> *f4c(C<T, I>*);
int *f4c(...);
void test_f4(D d, E e, F f) {
void test_f4(D d, E e, F f, G g) {
C<int, 1> *ci1a = f4a(d);
C<int, 1> *ci2a = f4a(e);
C<int, 1> *ci1b = f4b(d);
C<int, 1> *ci2b = f4b(e);
C<int, 1> *ci1c = f4c(&d);
C<int, 1> *ci2c = f4c(&e);
C<int, 1> *ci3c = f4c(&g);
int *ip1 = f4c(&f);
}