Reword a diagnostic; NFC

This diagnostic used to talk about complex integer types but is issued
for use of the increment or decrement operators on any complex type,
not just integral ones.

The diagnostic also had zero test coverage, so new coverage is added
along with the rewording.

Author: AaronBallman

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -7588,8 +7588,8 @@ def ext_gnu_ptr_func_arith : Extension<
   InGroup<GNUPointerArith>;
 def err_readonly_message_assignment : Error<
   "assigning to 'readonly' return result of an Objective-C message not allowed">;
-def ext_integer_increment_complex : Extension<
-  "ISO C does not support '++'/'--' on complex integer type %0">;
+def ext_increment_complex : Extension<
+  "'%select{--|++}0' on an object of complex type is a Clang extension">;
 def ext_integer_complement_complex : Extension<
   "ISO C does not support '~' for complex conjugation of %0">;
 def err_nosetter_property_assignment : Error<

clang/lib/Sema/SemaExpr.cpp

@@ -14859,8 +14859,8 @@ static QualType CheckIncrementDecrementOperand(Sema &S, Expr *Op,
       return QualType();
   } else if (ResType->isAnyComplexType()) {
     // C99 does not support ++/-- on complex types, we allow as an extension.
-    S.Diag(OpLoc, diag::ext_integer_increment_complex)
-      << ResType << Op->getSourceRange();
+    S.Diag(OpLoc, diag::ext_increment_complex)
+      << IsInc << Op->getSourceRange();
   } else if (ResType->isPlaceholderType()) {
     ExprResult PR = S.CheckPlaceholderExpr(Op);
     if (PR.isInvalid()) return QualType();

clang/test/Sema/complex-inc-dec.c

@@ -0,0 +1,24 @@
+// RUN: %clang_cc1 -verify -pedantic -std=c99 %s
+
+void func(void) {
+  _Complex float cf;
+  _Complex double cd;
+  _Complex long double cld;
+
+  ++cf;  // expected-warning {{'++' on an object of complex type is a Clang extension}}
+  ++cd;  // expected-warning {{'++' on an object of complex type is a Clang extension}}
+  ++cld; // expected-warning {{'++' on an object of complex type is a Clang extension}}
+
+  --cf;  // expected-warning {{'--' on an object of complex type is a Clang extension}}
+  --cd;  // expected-warning {{'--' on an object of complex type is a Clang extension}}
+  --cld; // expected-warning {{'--' on an object of complex type is a Clang extension}}
+
+  cf++;  // expected-warning {{'++' on an object of complex type is a Clang extension}}
+  cd++;  // expected-warning {{'++' on an object of complex type is a Clang extension}}
+  cld++; // expected-warning {{'++' on an object of complex type is a Clang extension}}
+
+  cf--;  // expected-warning {{'--' on an object of complex type is a Clang extension}}
+  cd--;  // expected-warning {{'--' on an object of complex type is a Clang extension}}
+  cld--; // expected-warning {{'--' on an object of complex type is a Clang extension}}
+}
+