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

Wraps the expansions of TYPE_SWITCH and COMPOSITE_TYPE_SWITCH in
the constexpr interpreter with "do { ... } while (0)" so that these
macros 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 review comment:
https://reviews.llvm.org/D64146?id=208520#inline-584131

Also cleaned up the macro definitions by removing the superfluous
do-while statements and removed the unused INT_TPYE_SWITCH macro.

Differential Revision: https://reviews.llvm.org/D117301

clang/lib/AST/Interp/PrimType.h

@@ -81,35 +81,27 @@ inline bool isPrimitiveIntegral(PrimType Type) {
 /// 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