Treating the unused equality comparisons as something other than part of

-Wunused was a mistake. It resulted in duplicate warnings and lots of
other hacks. Instead, this should be a special sub-category to
-Wunused-value, much like -Wunused-result is.

Moved to -Wunused-comparison, moved the implementation to piggy back on
the -Wunused-value implementation instead of rolling its own, different
mechanism for catching all of the "interesting" statements.

I like the unused-value mechanism for this better, but its currently
missing several top-level statements. For now, I've FIXME-ed out those
test cases. I'll enhance the generic infrastructure to catch these
statements in a subsequent patch.

This patch also removes the cast-to-void fixit hint. This hint isn't
available on any of the other -Wunused-value diagnostics, and if we want
it to be, we should add it generically rather than in one specific case.

llvm-svn: 137822

4 files changed, 88 insertions, 106 deletions

diff --git a/clang/test/Sema/unused-expr.c b/clang/test/Sema/unused-expr.c
index 9949887b23e..97611168f1a 100644
--- a/clang/test/Sema/unused-expr.c
+++ b/clang/test/Sema/unused-expr.c
@@ -7,11 +7,11 @@ double sqrt(double X);  // implicitly const because of no -fmath-errno!
 void bar(volatile int *VP, int *P, int A,
          _Complex double C, volatile _Complex double VC) {
   
-  VP == P;             // expected-warning {{expression result unused}}
+  VP < P;              // expected-warning {{expression result unused}}
   (void)A;
   (void)foo(1,2);      // no warning.
   
-  A == foo(1, 2);      // expected-warning {{expression result unused}}
+  A < foo(1, 2);       // expected-warning {{expression result unused}}
 
   foo(1,2)+foo(4,3);   // expected-warning {{expression result unused}}
 
@@ -54,23 +54,23 @@ void t4(int a) {
   int b = 0;
 
   if (a)
-    b == 1; // expected-warning{{expression result unused}}
+    b < 1; // expected-warning{{expression result unused}}
   else
-    b == 2; // expected-warning{{expression result unused}}
+    b < 2; // expected-warning{{expression result unused}}
     
   while (1)
-    b == 3; // expected-warning{{expression result unused}}
+    b < 3; // expected-warning{{expression result unused}}
 
   do
-    b == 4; // expected-warning{{expression result unused}}
+    b < 4; // expected-warning{{expression result unused}}
   while (1);
   
   for (;;)
-    b == 5; // expected-warning{{expression result unused}}
+    b < 5; // expected-warning{{expression result unused}}
     
-  for (b == 1;;) {} // expected-warning{{expression result unused}}
-  for (;b == 1;) {}
-  for (;;b == 1) {} // expected-warning{{expression result unused}}
+  for (b < 1;;) {} // expected-warning{{expression result unused}}
+  for (;b < 1;) {}
+  for (;;b < 1) {} // expected-warning{{expression result unused}}
 }
 
 // rdar://7186119
diff --git a/clang/test/SemaCXX/warn-top-level-comparison.cpp b/clang/test/SemaCXX/warn-top-level-comparison.cpp
deleted file mode 100644
index dad21aeedc0..00000000000
--- a/clang/test/SemaCXX/warn-top-level-comparison.cpp
+++ /dev/null
@@ -1,92 +0,0 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -Wtop-level-comparison -Wno-unused %s
-
-struct A {
-  bool operator==(const A&);
-  bool operator!=(const A&);
-  A operator|=(const A&);
-  operator bool();
-};
-
-void test() {
-  int x, *p;
-  A a, b;
-
-  x == 7; // expected-warning {{equality comparison as an unused top-level statement}} \
-          // expected-note {{cast this comparison to void to silence this warning}} \
-          // expected-note {{use '=' to turn this equality comparison into an assignment}}
-  x != 7; // expected-warning {{inequality comparison as an unused top-level statement}} \
-          // expected-note {{cast this comparison to void to silence this warning}} \
-          // expected-note {{use '|=' to turn this inequality comparison into an or-assignment}}
-  7 == x; // expected-warning {{equality comparison as an unused top-level statement}} \
-          // expected-note {{cast this comparison to void to silence this warning}}
-  p == p; // expected-warning {{equality comparison as an unused top-level statement}} \
-          // expected-note {{cast this comparison to void to silence this warning}} \
-          // expected-note {{use '=' to turn this equality comparison into an assignment}} \
-          // expected-warning {{self-comparison always evaluates to true}}
-  a == a; // expected-warning {{equality comparison as an unused top-level statement}} \
-          // expected-note {{cast this comparison to void to silence this warning}} \
-          // expected-note {{use '=' to turn this equality comparison into an assignment}}
-  a == b; // expected-warning {{equality comparison as an unused top-level statement}} \
-          // expected-note {{cast this comparison to void to silence this warning}} \
-          // expected-note {{use '=' to turn this equality comparison into an assignment}}
-  a != b; // expected-warning {{inequality comparison as an unused top-level statement}} \
-          // expected-note {{cast this comparison to void to silence this warning}} \
-          // expected-note {{use '|=' to turn this inequality comparison into an or-assignment}}
-  A() == b; // expected-warning {{equality comparison as an unused top-level statement}} \
-            // expected-note {{cast this comparison to void to silence this warning}}
-  if (42) x == 7; // expected-warning {{equality comparison as an unused top-level statement}} \
-                  // expected-note {{cast this comparison to void to silence this warning}} \
-                  // expected-note {{use '=' to turn this equality comparison into an assignment}}
-  else if (42) x == 7; // expected-warning {{equality comparison as an unused top-level statement}} \
-                       // expected-note {{cast this comparison to void to silence this warning}} \
-                       // expected-note {{use '=' to turn this equality comparison into an assignment}}
-  else x == 7; // expected-warning {{equality comparison as an unused top-level statement}} \
-               // expected-note {{cast this comparison to void to silence this warning}} \
-               // expected-note {{use '=' to turn this equality comparison into an assignment}}
-  do x == 7; // expected-warning {{equality comparison as an unused top-level statement}} \
-             // expected-note {{cast this comparison to void to silence this warning}} \
-             // expected-note {{use '=' to turn this equality comparison into an assignment}}
-  while (false);
-  while (false) x == 7; // expected-warning {{equality comparison as an unused top-level statement}} \
-                        // expected-note {{cast this comparison to void to silence this warning}} \
-                        // expected-note {{use '=' to turn this equality comparison into an assignment}}
-  for (x == 7; // expected-warning {{equality comparison as an unused top-level statement}} \
-               // expected-note {{cast this comparison to void to silence this warning}} \
-               // expected-note {{use '=' to turn this equality comparison into an assignment}}
-       x == 7; // No warning -- result is used
-       x == 7) // expected-warning {{equality comparison as an unused top-level statement}} \
-               // expected-note {{cast this comparison to void to silence this warning}} \
-               // expected-note {{use '=' to turn this equality comparison into an assignment}}
-    x == 7; // expected-warning {{equality comparison as an unused top-level statement}} \
-            // expected-note {{cast this comparison to void to silence this warning}} \
-            // expected-note {{use '=' to turn this equality comparison into an assignment}}
-  switch (42) default: x == 7; // expected-warning {{equality comparison as an unused top-level statement}} \
-                               // expected-note {{cast this comparison to void to silence this warning}} \
-                               // expected-note {{use '=' to turn this equality comparison into an assignment}}
-  switch (42) case 42: x == 7; // expected-warning {{equality comparison as an unused top-level statement}} \
-                               // expected-note {{cast this comparison to void to silence this warning}} \
-                               // expected-note {{use '=' to turn this equality comparison into an assignment}}
-  switch (42) {
-    case 1:
-    case 2:
-    default:
-    case 3:
-    case 4:
-      x == 7; // expected-warning {{equality comparison as an unused top-level statement}} \
-              // expected-note {{cast this comparison to void to silence this warning}} \
-              // expected-note {{use '=' to turn this equality comparison into an assignment}}
-  }
-
-  (void)(x == 7);
-  (void)(p == p); // expected-warning {{self-comparison always evaluates to true}}
-  { bool b = x == 7; }
-
-  { bool b = ({ x == 7; // expected-warning {{equality comparison as an unused top-level statement}} \
-                        // expected-note {{cast this comparison to void to silence this warning}} \
-                        // expected-note {{use '=' to turn this equality comparison into an assignment}}
-                x == 7; }); } // no warning on the second, its result is used!
-
-#define EQ(x,y) (x) == (y)
-  EQ(x, 5);
-#undef EQ
-}
diff --git a/clang/test/SemaCXX/warn-unused-comparison.cpp b/clang/test/SemaCXX/warn-unused-comparison.cpp
new file mode 100644
index 00000000000..79a644cefc0
--- /dev/null
+++ b/clang/test/SemaCXX/warn-unused-comparison.cpp
@@ -0,0 +1,72 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -Wno-unused -Wunused-comparison %s
+
+struct A {
+  bool operator==(const A&);
+  bool operator!=(const A&);
+  A operator|=(const A&);
+  operator bool();
+};
+
+void test() {
+  int x, *p;
+  A a, b;
+
+  x == 7; // expected-warning {{equality comparison result unused}} \
+          // expected-note {{use '=' to turn this equality comparison into an assignment}}
+  x != 7; // expected-warning {{inequality comparison result unused}} \
+          // expected-note {{use '|=' to turn this inequality comparison into an or-assignment}}
+  7 == x; // expected-warning {{equality comparison result unused}}
+  p == p; // expected-warning {{equality comparison result unused}} \
+          // expected-note {{use '=' to turn this equality comparison into an assignment}} \
+          // expected-warning {{self-comparison always evaluates to true}}
+  a == a; // FIXME: missing-warning {{equality comparison result unused}} \
+          // FIXME: missing-note {{use '=' to turn this equality comparison into an assignment}}
+  a == b; // FIXME: missing-warning {{equality comparison result unused}} \
+          // FIXME: missing-note {{use '=' to turn this equality comparison into an assignment}}
+  a != b; // FIXME: missing-warning {{inequality comparison result unused}} \
+          // FIXME: missing-note {{use '|=' to turn this inequality comparison into an or-assignment}}
+  A() == b; // FIXME: missing-warning {{equality comparison result unused}}
+  if (42) x == 7; // expected-warning {{equality comparison result unused}} \
+                  // expected-note {{use '=' to turn this equality comparison into an assignment}}
+  else if (42) x == 7; // expected-warning {{equality comparison result unused}} \
+                       // expected-note {{use '=' to turn this equality comparison into an assignment}}
+  else x == 7; // expected-warning {{equality comparison result unused}} \
+               // expected-note {{use '=' to turn this equality comparison into an assignment}}
+  do x == 7; // expected-warning {{equality comparison result unused}} \
+             // expected-note {{use '=' to turn this equality comparison into an assignment}}
+  while (false);
+  while (false) x == 7; // expected-warning {{equality comparison result unused}} \
+                        // expected-note {{use '=' to turn this equality comparison into an assignment}}
+  for (x == 7; // expected-warning {{equality comparison result unused}} \
+               // expected-note {{use '=' to turn this equality comparison into an assignment}}
+       x == 7; // No warning -- result is used
+       x == 7) // expected-warning {{equality comparison result unused}} \
+               // expected-note {{use '=' to turn this equality comparison into an assignment}}
+    x == 7; // expected-warning {{equality comparison result unused}} \
+            // expected-note {{use '=' to turn this equality comparison into an assignment}}
+  switch (42) default: x == 7; // FIXME: missing-warning {{equality comparison result unused}} \
+                               // FIXME: missing-note {{use '=' to turn this equality comparison into an assignment}}
+  switch (42) case 42: x == 7; // FIXME: missing-warning {{equality comparison result unused}} \
+                               // FIXME: missing-note {{use '=' to turn this equality comparison into an assignment}}
+  switch (42) {
+    case 1:
+    case 2:
+    default:
+    case 3:
+    case 4:
+      x == 7; // FIXME: missing-warning {{equality comparison result unused}} \
+              // FIXME: missing-note {{use '=' to turn this equality comparison into an assignment}}
+  }
+
+  (void)(x == 7);
+  (void)(p == p); // expected-warning {{self-comparison always evaluates to true}}
+  { bool b = x == 7; }
+
+  { bool b = ({ x == 7; // expected-warning {{equality comparison result unused}} \
+                        // expected-note {{use '=' to turn this equality comparison into an assignment}}
+                x == 7; }); } // no warning on the second, its result is used!
+
+#define EQ(x,y) (x) == (y)
+  EQ(x, 5);
+#undef EQ
+}
diff --git a/clang/test/SemaTemplate/resolve-single-template-id.cpp b/clang/test/SemaTemplate/resolve-single-template-id.cpp
index ef0a7630767..0c4656a8bc1 100644
--- a/clang/test/SemaTemplate/resolve-single-template-id.cpp
+++ b/clang/test/SemaTemplate/resolve-single-template-id.cpp
@@ -44,9 +44,10 @@ int main()
   !oneT<int>;  // expected-warning {{expression result unused}}
   +oneT<int>;  // expected-warning {{expression result unused}}
   -oneT<int>;  //expected-error {{invalid argument type}}
-  oneT<int> == 0;   // expected-warning {{expression result unused}}
-  0 == oneT<int>;   // expected-warning {{expression result unused}}
-  0 != oneT<int>;    // expected-warning {{expression result unused}}
+  oneT<int> == 0;   // expected-warning {{equality comparison result unused}} \
+                    // expected-note {{use '=' to turn this equality comparison into an assignment}}
+  0 == oneT<int>;   // expected-warning {{equality comparison result unused}}
+  0 != oneT<int>;    // expected-warning {{inequality comparison result unused}}
   (false ? one : oneT<int>);   // expected-warning {{expression result unused}}
   void (*p1)(int); p1 = oneT<int>;
   
@@ -67,7 +68,8 @@ int main()
 
   two < two; //expected-error {{cannot resolve overloaded function 'two' from context}}
   twoT<int> < twoT<int>; //expected-error {{cannot resolve overloaded function 'twoT' from context}}
-  oneT<int> == 0;   // expected-warning {{expression result unused}}
+  oneT<int> == 0;   // expected-warning {{equality comparison result unused}} \
+                    // expected-note {{use '=' to turn this equality comparison into an assignment}}
 
 }