[Concepts] Constrained partial specializations and function overloads.

Added support for constraint satisfaction checking and partial ordering of constraints in constrained partial specialization and function template overloads.
Re-commit after fixing another crash (added regression test).

Differential Revision: https://reviews.llvm.org/D41910

1 files changed, 89 insertions, 0 deletions

diff --git a/clang/test/CXX/temp/temp.constr/temp.constr.order/function-templates.cpp b/clang/test/CXX/temp/temp.constr/temp.constr.order/function-templates.cpp
new file mode 100644
index 00000000000..cc578fe0ad6
--- /dev/null
+++ b/clang/test/CXX/temp/temp.constr/temp.constr.order/function-templates.cpp
@@ -0,0 +1,89 @@
+// RUN: %clang_cc1 -std=c++2a -fconcepts-ts -x c++ -verify %s
+
+template<typename T> requires sizeof(T) >= 4
+bool a() { return false; } // expected-note {{candidate function [with T = unsigned int]}}
+
+template<typename T> requires sizeof(T) >= 4 && sizeof(T) <= 10
+bool a() { return true; } // expected-note {{candidate function [with T = unsigned int]}}
+
+bool av = a<unsigned>(); // expected-error {{call to 'a' is ambiguous}}
+
+template<typename T>
+concept C1 = sizeof(T) >= 4;
+
+template<typename T> requires C1<T>
+constexpr bool b() { return false; }
+
+template<typename T> requires C1<T> && sizeof(T) <= 10
+constexpr bool b() { return true; }
+
+static_assert(b<int>());
+static_assert(!b<int[10]>());
+
+template<typename T>
+concept C2 = sizeof(T) > 1 && sizeof(T) <= 8;
+
+template<typename T>
+bool c() { return false; }
+
+template<typename T> requires C1<T>
+bool c() { return true; }
+
+template<typename T> requires C1<T>
+constexpr bool d() { return false; }
+
+template<typename T>
+constexpr bool d() { return true; }
+
+static_assert(!d<int>());
+
+template<typename T>
+constexpr int e() { return 1; }
+
+template<typename T> requires C1<T> && C2<T>
+constexpr int e() { return 2; }
+
+template<typename T> requires C1<T> || C2<T>
+constexpr int e() { return 3; }
+
+static_assert(e<unsigned>() == 2);
+static_assert(e<char[10]>() == 3);
+static_assert(e<char>() == 1);
+
+template<class T, class U>
+concept BiggerThan = sizeof(T) > sizeof(U);
+
+template<class T>
+concept BiggerThanInt = BiggerThan<T, int>;
+
+template<class T, class U> requires BiggerThan<T, U>
+void f() { }
+// expected-note@-1 {{candidate function [with T = long long, U = int]}}
+
+template<class T, class U> requires BiggerThanInt<T>
+void f() { }
+// expected-note@-1 {{candidate function [with T = long long, U = int]}}
+
+static_assert(sizeof(f<long long, int>()));
+// expected-error@-1 {{call to 'f' is ambiguous}}
+
+template<typename T>
+concept C3 = true;
+
+template<typename T>
+concept C4 = true && C3<T>;
+
+template<typename T> requires C3<void>
+int g() { }
+
+template<typename T> requires C4<void>
+int g() { }
+
+static_assert(sizeof(g<int>()));
+
+// Regression - used template parameter detection when only first out of
+// multiple parameters are used
+template <unsigned> struct X {};
+template <class...> int h(X<0>);
+template <unsigned b, class...> int h(X<b>);
+static_assert(sizeof(h(X<0>{})));
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