PR c++/79228 - extensions hide C++14 complex literal operators

libcpp/
	* expr.c (interpret_float_suffix): Ignore 'i' in C++14 and up.
	(interpret_int_suffix): Likewise.
gcc/cp/
	* parser.c (cp_parser_userdef_numeric_literal): Be helpful about
	'i' in C++14 and up.

From-SVN: r255335

8 files changed, 138 insertions, 8 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 71f6f3a..89680a2 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2017-12-01  Jason Merrill  <jason@redhat.com>
+
+	PR c++/79228 - extensions hide C++14 complex literal operators
+	* parser.c (cp_parser_userdef_numeric_literal): Be helpful about
+	'i' in C++14 and up.
+
 2017-12-01  Jakub Jelinek  <jakub@redhat.com>
 
 	* parser.c (cp_parser_new): Don't clear cilk_simd_fn_info.
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index b469d1c..6e4c243 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -4397,11 +4397,75 @@ cp_parser_userdef_numeric_literal (cp_parser *parser)
 
   release_tree_vector (args);
 
-  error ("unable to find numeric literal operator %qD", name);
-  if (!cpp_get_options (parse_in)->ext_numeric_literals)
-    inform (token->location, "use -std=gnu++11 or -fext-numeric-literals "
+  /* In C++14 the standard library defines complex number suffixes that
+     conflict with GNU extensions.  Prefer them if <complex> is #included.  */
+  bool ext = cpp_get_options (parse_in)->ext_numeric_literals;
+  bool i14 = (cxx_dialect > cxx11
+	      && (id_equal (suffix_id, "i")
+		  || id_equal (suffix_id, "if")
+		  || id_equal (suffix_id, "il")));
+  diagnostic_t kind = DK_ERROR;
+  int opt = 0;
+
+  if (i14 && ext)
+    {
+      tree cxlit = lookup_qualified_name (std_node,
+					  get_identifier ("complex_literals"),
+					  0, false, false);
+      if (cxlit == error_mark_node)
+	{
+	  /* No <complex>, so pedwarn and use GNU semantics.  */
+	  kind = DK_PEDWARN;
+	  opt = OPT_Wpedantic;
+	}
+    }
+
+  bool complained
+    = emit_diagnostic (kind, input_location, opt,
+		       "unable to find numeric literal operator %qD", name);
+
+  if (!complained)
+    /* Don't inform either.  */;
+  else if (i14)
+    {
+      inform (token->location, "add %<using namespace std::complex_literals%> "
+	      "(from <complex>) to enable the C++14 user-defined literal "
+	      "suffixes");
+      if (ext)
+	inform (token->location, "or use %<j%> instead of %<i%> for the "
+		"GNU built-in suffix");
+    }
+  else if (!ext)
+    inform (token->location, "use -fext-numeric-literals "
 	    "to enable more built-in suffixes");
-  return error_mark_node;
+
+  if (kind == DK_ERROR)
+    value = error_mark_node;
+  else
+    {
+      /* Use the built-in semantics.  */
+      tree type;
+      if (id_equal (suffix_id, "i"))
+	{
+	  if (TREE_CODE (value) == INTEGER_CST)
+	    type = integer_type_node;
+	  else
+	    type = double_type_node;
+	}
+      else if (id_equal (suffix_id, "if"))
+	type = float_type_node;
+      else /* if (id_equal (suffix_id, "il")) */
+	type = long_double_type_node;
+
+      value = build_complex (build_complex_type (type),
+			     fold_convert (type, integer_zero_node),
+			     fold_convert (type, value));
+    }
+
+  if (cp_parser_uncommitted_to_tentative_parse_p (parser))
+    /* Avoid repeated diagnostics.  */
+    token->u.value = value;
+  return value;
 }
 
 /* Parse a user-defined string constant.  Returns a call to a user-defined
diff --git a/gcc/testsuite/g++.dg/cpp0x/gnu_fext-numeric-literals.C b/gcc/testsuite/g++.dg/cpp0x/gnu_fext-numeric-literals.C
index 6a8398b..ac2db28 100644
--- a/gcc/testsuite/g++.dg/cpp0x/gnu_fext-numeric-literals.C
+++ b/gcc/testsuite/g++.dg/cpp0x/gnu_fext-numeric-literals.C
@@ -4,7 +4,7 @@
 //  Integer imaginary...
 
 constexpr unsigned long long
-operator"" i(unsigned long long n) // { dg-warning "shadowed by implementation" }
+operator"" i(unsigned long long n) // { dg-warning "shadowed by implementation" "" { target c++11_only } }
 { return 4 * n + 0; }
 
 constexpr unsigned long long
@@ -22,7 +22,7 @@ operator"" J(unsigned long long n) // { dg-warning "shadowed by implementation"
 //  Floating-point imaginary...
 
 constexpr long double
-operator"" i(long double n) // { dg-warning "shadowed by implementation" }
+operator"" i(long double n) // { dg-warning "shadowed by implementation" "" { target c++11_only } }
 { return 4.0L * n + 0.0L; }
 
 constexpr long double
diff --git a/gcc/testsuite/g++.dg/cpp0x/std_fext-numeric-literals.C b/gcc/testsuite/g++.dg/cpp0x/std_fext-numeric-literals.C
index 7caaa7c..ff1e7b6 100644
--- a/gcc/testsuite/g++.dg/cpp0x/std_fext-numeric-literals.C
+++ b/gcc/testsuite/g++.dg/cpp0x/std_fext-numeric-literals.C
@@ -4,7 +4,7 @@
 //  Integer imaginary...
 
 constexpr unsigned long long
-operator"" i(unsigned long long n) // { dg-warning "shadowed by implementation" }
+operator"" i(unsigned long long n) // { dg-warning "shadowed by implementation" "" { target c++11_only } }
 { return 4 * n + 0; }
 
 constexpr unsigned long long
@@ -22,7 +22,7 @@ operator"" J(unsigned long long n) // { dg-warning "shadowed by implementation"
 //  Floating-point imaginary...
 
 constexpr long double
-operator"" i(long double n) // { dg-warning "shadowed by implementation" }
+operator"" i(long double n) // { dg-warning "shadowed by implementation" "" { target c++11_only } }
 { return 4.0L * n + 0.0L; }
 
 constexpr long double
diff --git a/gcc/testsuite/g++.dg/cpp1y/complex_literals1.C b/gcc/testsuite/g++.dg/cpp1y/complex_literals1.C
new file mode 100644
index 0000000..5ae2370
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/complex_literals1.C
@@ -0,0 +1,10 @@
+// PR c++/79228
+// { dg-do compile { target c++14 } }
+
+#include <complex>
+
+int main()
+{
+  using namespace std::complex_literals;
+  auto a = std::abs(0.0i);
+}
diff --git a/gcc/testsuite/g++.dg/cpp1y/complex_literals1a.C b/gcc/testsuite/g++.dg/cpp1y/complex_literals1a.C
new file mode 100644
index 0000000..9b61f3a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/complex_literals1a.C
@@ -0,0 +1,11 @@
+// PR c++/79228
+// { dg-do compile { target c++14 } }
+// { dg-options "" }
+
+#include <complex>
+
+int main()
+{
+  auto a = std::abs(0.0i);	// { dg-error "literal operator" }
+  // { dg-message "complex_literals" "" { target *-*-* } .-1 }
+}
diff --git a/gcc/testsuite/g++.dg/cpp1y/complex_literals2.C b/gcc/testsuite/g++.dg/cpp1y/complex_literals2.C
new file mode 100644
index 0000000..6dd9947
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/complex_literals2.C
@@ -0,0 +1,25 @@
+// PR c++/79228
+// { dg-do compile { target c++14 } }
+// { dg-options "-Wpedantic" }
+
+template <class,class> struct same;
+template <class T> struct same<T,T> { };
+
+int main()
+{
+  same<decltype(0i),__complex int>{}; // { dg-warning "literal operator" }
+  // { dg-message "complex_literals" "" { target *-*-* } .-1 }
+  // { dg-message "built-in" "" { target *-*-* } .-2 }
+
+  same<decltype(0.0i),__complex double>{}; // { dg-warning "literal operator" }
+  // { dg-message "complex_literals" "" { target *-*-* } .-1 }
+  // { dg-message "built-in" "" { target *-*-* } .-2 }
+
+  same<decltype(0.0if),__complex float>{}; // { dg-warning "literal operator" }
+  // { dg-message "complex_literals" "" { target *-*-* } .-1 }
+  // { dg-message "built-in" "" { target *-*-* } .-2 }
+
+  same<decltype(0.0il),__complex long double>{}; // { dg-warning "literal operator" }
+  // { dg-message "complex_literals" "" { target *-*-* } .-1 }
+  // { dg-message "built-in" "" { target *-*-* } .-2 }
+}
diff --git a/gcc/testsuite/g++.dg/cpp1y/complex_literals2a.C b/gcc/testsuite/g++.dg/cpp1y/complex_literals2a.C
new file mode 100644
index 0000000..9ee9f3f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/complex_literals2a.C
@@ -0,0 +1,14 @@
+// PR c++/79228
+// { dg-do compile { target c++14 } }
+// { dg-options "" }
+
+template <class,class> struct same;
+template <class T> struct same<T,T> { };
+
+int main()
+{
+  same<decltype(0i),__complex int>{};
+  same<decltype(0.0i),__complex double>{};
+  same<decltype(0.0if),__complex float>{};
+  same<decltype(0.0il),__complex long double>{};
+}