Rearchitect -Wconversion and -Wsign-compare. Instead of computing them

"bottom-up" when implicit casts and comparisons are inserted, compute them
"top-down" when the full expression is finished.  Makes it easier to
coordinate warnings and thus implement -Wconversion for signedness
conversions without double-warning with -Wsign-compare.  Also makes it possible
to realize that a signedness conversion is okay because the context is
performing the inverse conversion.  Also simplifies some logic that was
trying to calculate the ultimate comparison/result type and getting it wrong.
Also fixes a problem with the C++ explicit casts which are often "implemented"
in the AST with a series of implicit cast expressions.

llvm-svn: 103174

1 files changed, 8 insertions, 1 deletions

diff --git a/clang/test/Sema/conditional-expr.c b/clang/test/Sema/conditional-expr.c
index 5e2c1a46248..6e248bc3cfe 100644
--- a/clang/test/Sema/conditional-expr.c
+++ b/clang/test/Sema/conditional-expr.c
@@ -52,7 +52,9 @@ void foo() {
   enum Enum { EVal };
   test0 = test0 ? EVal : test0;
   test0 = test0 ? EVal : (int) test0; // okay: EVal is an int
-  test0 = test0 ? (unsigned) EVal : (int) test0; // expected-warning {{operands of ? are integers of different signs}}
+  test0 = test0 ? // expected-warning {{operands of ? are integers of different signs}}
+                  (unsigned) EVal
+                : (int) test0;
 }
 
 int Postgresql() {
@@ -68,3 +70,8 @@ int f0(int a) {
   // GCC considers this a warning.
   return a ? f1() : nil; // expected-warning {{pointer/integer type mismatch in conditional expression ('int' and 'void *')}} expected-warning {{incompatible pointer to integer conversion returning 'void *' from a function with result type 'int'}}
 }
+
+int f2(int x) {
+  // We can suppress this because the immediate context wants an int.
+  return (x != 0) ? 0U : x;
+}