P0859R0: List-initialization is potentially-constant-evaluated and
triggers instantiation of constexpr functions.
We mostly implemented this since Clang 6, but missed the template
instantiation case.
We do not implement the '&cast-expression' special case. It appears to
be a mistake / oversight. I've mailed CWG to see if we can remove it.
llvm-svn: 343064
diff --git a/clang/test/CXX/expr/expr.const/p6.cpp b/clang/test/CXX/expr/expr.const/p6.cpp
new file mode 100644
index 0000000..a8fc775
--- /dev/null
+++ b/clang/test/CXX/expr/expr.const/p6.cpp
@@ -0,0 +1,39 @@
+// RUN: %clang_cc1 -std=c++17 -verify %s
+
+template<typename T> int not_constexpr() { return T::error; }
+template<typename T> constexpr int is_constexpr() { return T::error; } // expected-error {{'::'}}
+
+template<typename T> int not_constexpr_var = T::error;
+template<typename T> constexpr int is_constexpr_var = T::error; // expected-error {{'::'}}
+template<typename T> const int is_const_var = T::error; // expected-error {{'::'}}
+template<typename T> const volatile int is_const_volatile_var = T::error;
+template<typename T> T is_dependent_var = T::error; // expected-error {{'::'}}
+template<typename T> int &is_reference_var = T::error; // expected-error {{'::'}}
+template<typename T> float is_float_var = T::error;
+
+void test() {
+ // Do not instantiate functions referenced in unevaluated operands...
+ (void)sizeof(not_constexpr<long>());
+ (void)sizeof(is_constexpr<long>());
+ (void)sizeof(not_constexpr_var<long>);
+ (void)sizeof(is_constexpr_var<long>);
+ (void)sizeof(is_const_var<long>);
+ (void)sizeof(is_const_volatile_var<long>);
+ (void)sizeof(is_dependent_var<long>);
+ (void)sizeof(is_dependent_var<const long>);
+ (void)sizeof(is_reference_var<long>);
+ (void)sizeof(is_float_var<long>);
+
+ // ... but do if they are potentially constant evaluated, and refer to
+ // constexpr functions or to variables usable in constant expressions.
+ (void)sizeof(int{not_constexpr<int>()});
+ (void)sizeof(int{is_constexpr<int>()}); // expected-note {{instantiation of}}
+ (void)sizeof(int{not_constexpr_var<int>});
+ (void)sizeof(int{is_constexpr_var<int>}); // expected-note {{instantiation of}}
+ (void)sizeof(int{is_const_var<int>}); // expected-note {{instantiation of}}
+ (void)sizeof(int{is_const_volatile_var<int>});
+ (void)sizeof(int{is_dependent_var<int>});
+ (void)sizeof(int{is_dependent_var<const int>}); // expected-note {{instantiation of}}
+ (void)sizeof(int{is_reference_var<int>}); // expected-note {{instantiation of}}
+ (void)sizeof(int{is_float_var<int>}); // expected-error {{cannot be narrowed}} expected-note {{cast}}
+}