Fix handling of preincrement on bit-fields. This gives a bit-field in C++, but

we were failing to find that bit-field when performing integer promotions. This
brings us closer to following the standard, and closer to GCC.

In C, this change is technically a regression: we get bit-field promotions
completely wrong in C, promoting cases that are categorically not bit-field
designators. This change makes us do so slightly more consistently, though.

llvm-svn: 218428

1 files changed, 32 insertions, 0 deletions

diff --git a/clang/test/SemaCXX/bitfield.cpp b/clang/test/SemaCXX/bitfield.cpp
new file mode 100644
index 00000000000..083c28ffbb3
--- /dev/null
+++ b/clang/test/SemaCXX/bitfield.cpp
@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 %s -verify
+
+// expected-no-diagnostics
+
+namespace PromotionVersusMutation {
+  typedef unsigned Unsigned;
+  typedef signed Signed;
+
+  struct T { unsigned n : 2; } t;
+
+  typedef __typeof__(t.n) Unsigned; // Bitfield is unsigned
+  typedef __typeof__(+t.n) Signed;  // ... but promotes to signed.
+
+  typedef __typeof__(t.n + 0) Signed; // Arithmetic promotes.
+
+  typedef __typeof__(t.n = 0) Unsigned;  // Assignment produces an lvalue...
+  typedef __typeof__(t.n += 0) Unsigned;
+  typedef __typeof__(t.n *= 0) Unsigned;
+  typedef __typeof__(+(t.n = 0)) Signed;  // ... which is a bit-field.
+  typedef __typeof__(+(t.n += 0)) Signed;
+  typedef __typeof__(+(t.n *= 0)) Signed;
+
+  typedef __typeof__(++t.n) Unsigned; // Increment is equivalent to compound-assignment.
+  typedef __typeof__(--t.n) Unsigned;
+  typedef __typeof__(+(++t.n)) Signed;
+  typedef __typeof__(+(--t.n)) Signed;
+
+  typedef __typeof__(t.n++) Unsigned; // Post-increment's result has the type
+  typedef __typeof__(t.n--) Unsigned; // of the operand...
+  typedef __typeof__(+(t.n++)) Unsigned; // ... and is not a bit-field (because
+  typedef __typeof__(+(t.n--)) Unsigned; // it's not a glvalue).
+}