[clang][NFC] Wrap TYPE_SWITCH in "do while (0)" in the interpreter

[owenpan]

Summary

Wraps the expansion of TYPE_SWITCH of the constexpr interpreter
in do { ... } while (0) so that the macro can be used like this:

if (llvm::Optional<PrimType> T = Ctx.classify(FieldTy)) 
  TYPE_SWITCH(*T, Ok &= ReturnValue<T>(FP.deref<T>(), Value));
else 
  Ok &= Composite(FieldTy, FP, Value);

This bug was found while testing D116316. See also this review comment.

[RKSimon]

what about COMPOSITE_TYPE_SWITCH and INT_TYPE_SWITCH - should they be updated as well?

[owenpan]

In D117301#3253874, @RKSimon wrote:

what about COMPOSITE_TYPE_SWITCH and INT_TYPE_SWITCH - should they be updated as well?

I left them alone because COMPOSITE_TYPE_SWITCH didn't cause a dangling else problem and INT_TYPE_SWITCH was not used at all. I can fix them both or fix the former and remvoe the latter from the header file. Also, the current do { ... } while (0) statements in TYPE_SWITCH_CASE and COMPOSITE_TYPE_SWITCH are superfluous. I can remove them as well.

[owenpan]

• Also wrapped COMPOSITE_TYPE_SWITCH with do-while.
• Cleaned up the macro definitions by removing the superfluous do-while statements.
• Removed the unused INT_TPYE_SWITCH macro.

[RKSimon]

LGTM - cheers

clang/lib/AST/Interp/PrimType.h

 }
 
 } // namespace interp
 } // namespace clang
 
 /// Helper macro to simplify type switches.
 /// The macro implicitly exposes a type T in the scope of the inner block.
 #define TYPE_SWITCH_CASE(Name, B) \
-  case Name: { using T = PrimConv<Name>::T; do {B;} while(0); break; }
+  case Name: { using T = PrimConv<Name>::T; B; break; }
 #define TYPE_SWITCH(Expr, B)                                                   \
-  switch (Expr) {                                                              \
-    TYPE_SWITCH_CASE(PT_Sint8, B)                                              \
-    TYPE_SWITCH_CASE(PT_Uint8, B)                                              \
-    TYPE_SWITCH_CASE(PT_Sint16, B)                                             \
-    TYPE_SWITCH_CASE(PT_Uint16, B)                                             \
-    TYPE_SWITCH_CASE(PT_Sint32, B)                                             \
-    TYPE_SWITCH_CASE(PT_Uint32, B)                                             \
-    TYPE_SWITCH_CASE(PT_Sint64, B)                                             \
-    TYPE_SWITCH_CASE(PT_Uint64, B)                                             \
-    TYPE_SWITCH_CASE(PT_Bool, B)                                               \
-    TYPE_SWITCH_CASE(PT_Ptr, B)                                                \
-  }
+  do {                                                                         \
+    switch (Expr) {                                                            \
+      TYPE_SWITCH_CASE(PT_Sint8, B)                                            \
+      TYPE_SWITCH_CASE(PT_Uint8, B)                                            \
+      TYPE_SWITCH_CASE(PT_Sint16, B)                                           \
+      TYPE_SWITCH_CASE(PT_Uint16, B)                                           \
+      TYPE_SWITCH_CASE(PT_Sint32, B)                                           \
+      TYPE_SWITCH_CASE(PT_Uint32, B)                                           \
+      TYPE_SWITCH_CASE(PT_Sint64, B)                                           \
+      TYPE_SWITCH_CASE(PT_Uint64, B)                                           \
+      TYPE_SWITCH_CASE(PT_Bool, B)                                             \
+      TYPE_SWITCH_CASE(PT_Ptr, B)                                              \
+    }                                                                          \
+  } while (0)
 #define COMPOSITE_TYPE_SWITCH(Expr, B, D)                                      \
-  switch (Expr) {                                                              \
-    TYPE_SWITCH_CASE(PT_Ptr, B)                                                \
-    default: do { D; } while(0); break;                                        \
-  }
-#define INT_TYPE_SWITCH(Expr, B)                                               \
-  switch (Expr) {                                                              \
-    TYPE_SWITCH_CASE(PT_Sint8, B)                                              \
-    TYPE_SWITCH_CASE(PT_Uint8, B)                                              \
-    TYPE_SWITCH_CASE(PT_Sint16, B)                                             \
-    TYPE_SWITCH_CASE(PT_Uint16, B)                                             \
-    TYPE_SWITCH_CASE(PT_Sint32, B)                                             \
-    TYPE_SWITCH_CASE(PT_Uint32, B)                                             \
-    TYPE_SWITCH_CASE(PT_Sint64, B)                                             \
-    TYPE_SWITCH_CASE(PT_Uint64, B)                                             \
-    default: llvm_unreachable("not an integer");                               \
-  }
+  do {                                                                         \
+    switch (Expr) {                                                            \
+      TYPE_SWITCH_CASE(PT_Ptr, B)                                              \
+      default: { D; break; }                                                   \
+    }                                                                          \
+  } while (0)
 #endif