[Clang] Make the SizeType, SignedSizeType and PtrdiffType be named sugar types instead of built-in types (#143653)

Including the results of `sizeof`, `sizeof...`, `__datasizeof`,
`__alignof`, `_Alignof`, `alignof`, `_Countof`, `size_t` literals, and
signed `size_t` literals, the results of pointer-pointer subtraction and
checks for standard library functions (and their calls).

The goal is to enable clang and downstream tools such as clangd and
clang-tidy to provide more portable hints and diagnostics.

The previous discussion can be found at #136542.

This PR implements this feature by introducing a new subtype of `Type`
called `PredefinedSugarType`, which was considered appropriate in
discussions. I tried to keep `PredefinedSugarType` simple enough yet not
limited to `size_t` and `ptrdiff_t` so that it can be used for other
purposes. `PredefinedSugarType` wraps a canonical `Type` and provides a
name, conceptually similar to a compiler internal `TypedefType` but
without depending on a `TypedefDecl` or a source file.

Additionally, checks for the `z` and `t` format specifiers in format
strings for `scanf` and `printf` were added. It will precisely match
expressions using `typedef`s or built-in expressions.

The affected tests indicates that it works very well.

Several code require that `SizeType` is canonical, so I kept `SizeType`
to its canonical form.

The failed tests in CI are allowed to fail. See the
[comment](https://github.com/llvm/llvm-project/pull/135386#issuecomment-3049426611)
in another PR #135386.

4 files changed, 17 insertions, 6 deletions

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index dd5b710..5e523fe 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -5239,7 +5239,9 @@ bool Sema::BuiltinVAStartARMMicrosoft(CallExpr *Call) {
         << 2 << Arg1->getType() << ConstCharPtrTy;
 
   const QualType SizeTy = Context.getSizeType();
-  if (Arg2Ty->getCanonicalTypeInternal().withoutLocalFastQualifiers() != SizeTy)
+  if (!Context.hasSameType(
+          Arg2Ty->getCanonicalTypeInternal().withoutLocalFastQualifiers(),
+          SizeTy))
     Diag(Arg2->getBeginLoc(), diag::err_typecheck_convert_incompatible)
         << Arg2->getType() << SizeTy << 1 /* different class */
         << 0                              /* qualifier difference */
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 728ada3..45c7178 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -4564,6 +4564,9 @@ static void captureVariablyModifiedType(ASTContext &Context, QualType T,
     case Type::Atomic:
       T = cast<AtomicType>(Ty)->getValueType();
       break;
+    case Type::PredefinedSugar:
+      T = cast<PredefinedSugarType>(Ty)->desugar();
+      break;
     }
   } while (!T.isNull() && T->isVariablyModifiedType());
 }
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index fd95f4e..0edfd60 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -3461,11 +3461,11 @@ void Sema::DeclareGlobalAllocationFunction(DeclarationName Name,
     // non-templated allocation function we are trying to declare here.
     if (FunctionDecl *Func = dyn_cast<FunctionDecl>(*Alloc)) {
       if (Func->getNumParams() == Params.size()) {
-        llvm::SmallVector<QualType, 3> FuncParams;
-        for (auto *P : Func->parameters())
-          FuncParams.push_back(
-              Context.getCanonicalType(P->getType().getUnqualifiedType()));
-        if (llvm::ArrayRef(FuncParams) == Params) {
+        if (std::equal(Func->param_begin(), Func->param_end(), Params.begin(),
+                       Params.end(), [&](ParmVarDecl *D, QualType RT) {
+                         return Context.hasSameUnqualifiedType(D->getType(),
+                                                               RT);
+                       })) {
           // Make the function visible to name lookup, even if we found it in
           // an unimported module. It either is an implicitly-declared global
           // allocation function, or is suppressing that function.
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 286c2b4..c7428d1 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -7245,6 +7245,12 @@ QualType TreeTransform<Derived>::TransformDependentBitIntType(
   return Result;
 }
 
+template <typename Derived>
+QualType TreeTransform<Derived>::TransformPredefinedSugarType(
+    TypeLocBuilder &TLB, PredefinedSugarTypeLoc TL) {
+  llvm_unreachable("This type does not need to be transformed.");
+}
+
   /// Simple iterator that traverses the template arguments in a
   /// container that provides a \c getArgLoc() member function.
   ///