[PATCH] [AST] Introduce a new DecayedType sugar node

[Reid Kleckner]

================
Comment at: lib/Sema/SemaType.cpp:3576-3578
@@ -3579,2 +3575,5 @@
     }
+    void VisitDecayedTypeLoc(DecayedTypeLoc TL) {
+      llvm_unreachable("decayed type locs not expected here!");
+    }
 
----------------
Richard Smith wrote:
> How do we ever fill in a DecayedTypeLoc's inner type?
Decayed types are never returned by GetTypeForDeclarator(), so we never call DeclaratorLocFiller on it.  Alternatively I can make it do nothing, but it's dead code.

================
Comment at: lib/Serialization/ASTReader.cpp:4523-4526
@@ +4522,6 @@
+    QualType OriginalType = readType(*Loc.F, Record, Idx);
+    QualType DT = Context.getMaybeDecayedType(OriginalType);
+    if (!isa<DecayedType>(DT))
+      Error("Decayed type does not decay");
+    return DT;
+  }
----------------
Richard Smith wrote:
> This is just 'return Context.getDecayedType(OriginalType);', right?
The difference is that this doesn't assert, it calls Error() and tries to recover.

================
Comment at: lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp:599-602
@@ -598,5 +598,6 @@
   if (FTP->getNumArgs() == 1) {
-    // Is the argument an 'unsigned short *'?
+    // Is the canonical argument type 'unsigned short *'?
     // (Actually any integer type is allowed.)
-    const PointerType *PT = dyn_cast<PointerType>(FTP->getArgType(0));
+    const PointerType *PT =
+        dyn_cast<PointerType>(FTP->getArgType(0).getCanonicalType());
     if (!PT)
----------------
Richard Smith wrote:
> This should be replaced with FTP->getArgType(0)->getAs<PointerType>().
Done here and elsewhere.

================
Comment at: tools/libclang/CIndex.cpp:1550-1553
@@ +1549,6 @@
+bool CursorVisitor::VisitDecayedTypeLoc(DecayedTypeLoc TL) {
+  if (Visit(TL.getOriginalLoc()))
+    return true;
+
+  return false;
+}
----------------
Richard Smith wrote:
> 'return Visit(TL.getOriginalLoc());' ?
Done.

================
Comment at: include/clang/AST/ASTContext.h:895-897
@@ +894,5 @@
+
+  /// \brief Returns a DecayedType if T is an array or function.  Otherwise
+  /// returns T.  Call this instead of getDecayedType() if T's type is unknown.
+  QualType getMaybeDecayedType(QualType T) const;
+
----------------
Richard Smith wrote:
> Please rename to getAdjustedParameterType, and make the existing getAdjustedParameterType local to ASTContext.cpp. I don't think we want to expose a way to perform parameter type decay that doesn't build a DecayedType node.
OK.

================
Comment at: include/clang/AST/RecursiveASTVisitor.h:850-853
@@ -849,1 +849,6 @@
 
+DEF_TRAVERSE_TYPE(DecayedType, {
+    TRY_TO(TraverseType(T->getDecayedType()));
+    TRY_TO(TraverseType(T->getOriginalType()));
+  })
+
----------------
Richard Smith wrote:
> Seems a bit weird to me to visit both types here. I also worry that this will be exponential-time if we have deeply-nested functions-taking-functions-taking-functions. I suggest you follow our behavior for AttributedType here and visit the original type, not the desugared type.
Sounds good.  I wasn't really sure what to do.


http://llvm-reviews.chandlerc.com/D1014