Make CastExpr::getSubExprAsWritten look through implicit temporary under CK_ConstructorConversion

[sberg]

Summary

With

struct S1 {};
struct S2 { operator S1(); };
S1 f(S2 s) { return static_cast<S1>(s); }

the static_cast expr is

CXXStaticCastExpr 0x... 'struct S1' static_cast<struct S1> <ConstructorConversion>
`-CXXConstructExpr 0x... 'struct S1' 'void (struct S1 &&) noexcept' elidable

`-MaterializeTemporaryExpr 0x... 'struct S1' xvalue
  `-ImplicitCastExpr 0x... 'struct S1' <UserDefinedConversion>
    `-CXXMemberCallExpr 0x... 'struct S1'
      `-MemberExpr 0x... '<bound member function type>' .operator S1 0x...
        `-DeclRefExpr 0x... 'struct S2' lvalue ParmVar 0x... 's' 'struct S2'

getSubExprAsWritten used to return the MaterializeTemporaryExpr (of type S1) under the CXXConstructExpr, instead of unwinding further to the DeclRefExpr (of type S2) at the bottom.

[sberg]

(I'm not sure where and how to add a test for this?)

[sberg]

added test

cfe/trunk/lib/AST/Expr.cpp

 const char *CastExpr::getCastKindName() const {
   switch (getCastKind()) {
 #define CAST_OPERATION(Name) case CK_##Name: return #Name;
 #include "clang/AST/OperationKinds.def"
   }
   llvm_unreachable("Unhandled cast kind!");
 }
 
-Expr *CastExpr::getSubExprAsWritten() {
-  Expr *SubExpr = nullptr;
-  CastExpr *E = this;
-  do {
-    SubExpr = E->getSubExpr();
-
+namespace {
+  Expr *skipImplicitTemporary(Expr *expr) {
     // Skip through reference binding to temporary.
-    if (MaterializeTemporaryExpr *Materialize 
-                                  = dyn_cast<MaterializeTemporaryExpr>(SubExpr))
-      SubExpr = Materialize->GetTemporaryExpr();
-        
+    if (MaterializeTemporaryExpr *Materialize
+                                  = dyn_cast<MaterializeTemporaryExpr>(expr))
+      expr = Materialize->GetTemporaryExpr();
     // Skip any temporary bindings; they're implicit.
-    if (CXXBindTemporaryExpr *Binder = dyn_cast<CXXBindTemporaryExpr>(SubExpr))
-      SubExpr = Binder->getSubExpr();
-    
+    if (CXXBindTemporaryExpr *Binder = dyn_cast<CXXBindTemporaryExpr>(expr))
+      expr = Binder->getSubExpr();
+
+    return expr;
+  }
+}
+
+Expr *CastExpr::getSubExprAsWritten() {
+  Expr *SubExpr = nullptr;
+  CastExpr *E = this;
+  do {
+    SubExpr = skipImplicitTemporary(E->getSubExpr());
     // Conversions by constructor and conversion functions have a
     // subexpression describing the call; strip it off.
     if (E->getCastKind() == CK_ConstructorConversion)
-      SubExpr = cast<CXXConstructExpr>(SubExpr)->getArg(0);
+      SubExpr =
+        skipImplicitTemporary(cast<CXXConstructExpr>(SubExpr)->getArg(0));
     else if (E->getCastKind() == CK_UserDefinedConversion) {
       assert((isa<CXXMemberCallExpr>(SubExpr) ||
               isa<BlockExpr>(SubExpr)) &&
              "Unexpected SubExpr for CK_UserDefinedConversion.");
       if (isa<CXXMemberCallExpr>(SubExpr))
         SubExpr = cast<CXXMemberCallExpr>(SubExpr)->getImplicitObjectArgument();
     }
     

cfe/trunk/unittests/Tooling/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   ${LLVM_TARGETS_TO_BUILD}
   Support
   )
 
 # By default MSVC has a 2^16 limit on the number of sections in an object file,
 # and this needs more than that.
 if (MSVC)
   set_source_files_properties(RecursiveASTVisitorTest.cpp PROPERTIES COMPILE_FLAGS /bigobj)
   set_source_files_properties(RecursiveASTVisitorTestExprVisitor.cpp PROPERTIES COMPILE_FLAGS /bigobj)
 endif()
 
 add_clang_unittest(ToolingTests
+  CastExprTest.cpp
   CommentHandlerTest.cpp
   CompilationDatabaseTest.cpp
   FixItTest.cpp
   LookupTest.cpp
   QualTypeNamesTest.cpp
   RecursiveASTVisitorTest.cpp
   RecursiveASTVisitorTestCallVisitor.cpp
   RecursiveASTVisitorTestDeclVisitor.cpp

cfe/trunk/unittests/Tooling/CastExprTest.cpp

+//===- unittest/Tooling/CastExprTest.cpp ----------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "TestVisitor.h"
+
+using namespace clang;
+
+namespace {
+
+struct CastExprVisitor : TestVisitor<CastExprVisitor> {
+  std::function<void(ExplicitCastExpr *)> OnExplicitCast;
+
+  bool VisitExplicitCastExpr(ExplicitCastExpr *Expr) {
+    if (OnExplicitCast)
+      OnExplicitCast(Expr);
+    return true;
+  }
+};
+
+TEST(CastExprTest, GetSubExprAsWrittenThroughMaterializedTemporary) {
+    CastExprVisitor Visitor;
+    Visitor.OnExplicitCast = [](ExplicitCastExpr *Expr) {
+      auto Sub = Expr->getSubExprAsWritten();
+      EXPECT_TRUE(isa<DeclRefExpr>(Sub))
+        << "Expected DeclRefExpr, but saw " << Sub->getStmtClassName();
+    };
+    Visitor.runOver("struct S1 {};\n"
+                    "struct S2 { operator S1(); };\n"
+                    "S1 f(S2 s) { return static_cast<S1>(s); }\n");
+}
+
+}