[PATCH] D21145: [Sema] Fix crash on valid where instantiation of lambda cannot access type of 'this'

[Erik Pilkington via cfe-commits]

erik.pilkington updated this revision to Diff 60622.
erik.pilkington added a comment.

This patch removes the handmade loop from `Sema::getCurrentThisType` instead just using the result of `Sema::getFunctionLevelDeclContext`. I believe that this will always give us the nearest `CXXRecordDecl` that we're looking for (right?).

For what it's worth, I agree with (Saturday) you that `Sema::getCurrentThisType` should be able to handle this case. That being said it seems at the very least quirky that `int x; x = y;` and `int x = y;` take an entirely different path through `getCurrentThisType` for `y` in a lambda initializer (the first using the CXXThisTypeOverride path).

@faisalv: Waffles are definitely not a problem, if that's what it takes to get the right fix! Thanks again for helping.


http://reviews.llvm.org/D21145

Files:
  lib/Sema/SemaExprCXX.cpp
  test/SemaCXX/lambda-expressions.cpp

Index: test/SemaCXX/lambda-expressions.cpp
===================================================================
--- test/SemaCXX/lambda-expressions.cpp
+++ test/SemaCXX/lambda-expressions.cpp
@@ -1,5 +1,4 @@
-// RUN: %clang_cc1 -std=c++11 -Wno-unused-value -fsyntax-only -verify -fblocks %s
-// RUN: %clang_cc1 -std=c++1y -Wno-unused-value -fsyntax-only -verify -fblocks %s
+// RUN: %clang_cc1 -std=c++14 -Wno-unused-value -fsyntax-only -verify -fblocks %s
 
 namespace std { class type_info; };
 
@@ -499,3 +498,30 @@
   };
 }
 }
+
+namespace PR27994 {
+struct A { template <class T> A(T); };
+
+template <class T>
+struct B {
+  int x;
+  A a = [&] { int y = x; };
+  A b = [&] { [&] { [&] { int y = x; }; }; };
+  A d = [&](auto param) { int y = x; };
+  A e = [&](auto param) { [&] { [&](auto param2) { int y = x; }; }; };
+};
+
+B<int> b;
+
+template <class T> struct C {
+  struct D {
+    int x;
+    A f = [&] { int y = x; };
+  };
+};
+
+int func() {
+  C<int> a;
+  decltype(a)::D b;
+}
+}
Index: lib/Sema/SemaExprCXX.cpp
===================================================================
--- lib/Sema/SemaExprCXX.cpp
+++ lib/Sema/SemaExprCXX.cpp
@@ -961,32 +961,23 @@
 QualType Sema::getCurrentThisType() {
   DeclContext *DC = getFunctionLevelDeclContext();
   QualType ThisTy = CXXThisTypeOverride;
+
   if (CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(DC)) {
     if (method && method->isInstance())
       ThisTy = method->getThisType(Context);
   }
-  if (ThisTy.isNull()) {
-    if (isGenericLambdaCallOperatorSpecialization(CurContext) &&
-        CurContext->getParent()->getParent()->isRecord()) {
-      // This is a generic lambda call operator that is being instantiated
-      // within a default initializer - so use the enclosing class as 'this'.
-      // There is no enclosing member function to retrieve the 'this' pointer
-      // from.
-
-      // FIXME: This looks wrong. If we're in a lambda within a lambda within a
-      // default member initializer, we need to recurse up more parents to find
-      // the right context. Looks like we should be walking up to the parent of
-      // the closure type, checking whether that is itself a lambda, and if so,
-      // recursing, until we reach a class or a function that isn't a lambda
-      // call operator. And we should accumulate the constness of *this on the
-      // way.
-
-      QualType ClassTy = Context.getTypeDeclType(
-          cast<CXXRecordDecl>(CurContext->getParent()->getParent()));
-      // There are no cv-qualifiers for 'this' within default initializers, 
-      // per [expr.prim.general]p4.
-      ThisTy = Context.getPointerType(ClassTy);
-    }
+
+  if (ThisTy.isNull() && isLambdaCallOperator(CurContext) &&
+      !ActiveTemplateInstantiations.empty()) {
+
+    // This is a lambda call operator that is being instantiated as a default
+    // initializer. DC must point to the enclosing class type, so we can recover
+    // the 'this' type from it.
+
+    QualType ClassTy = Context.getTypeDeclType(cast<CXXRecordDecl>(DC));
+    // There are no cv-qualifiers for 'this' within default initializers,
+    // per [expr.prim.general]p4.
+    ThisTy = Context.getPointerType(ClassTy);
   }
 
   // If we are within a lambda's call operator, the cv-qualifiers of 'this'


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D21145.60622.patch
Type: text/x-patch
Size: 3290 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20160613/e5a70107/attachment-0001.bin>