r276900 - [Sema] Teach getCurrentThisType to reconize lambda in in-class initializer

[Richard Smith via cfe-commits]

Yes, this should be merged. It's not quite right, but it's certainly better
than what we had before.

On Mon, Aug 8, 2016 at 1:34 PM, Hans Wennborg <hans at chromium.org> wrote:

> Richard: ping?
>
> On Wed, Jul 27, 2016 at 4:46 PM, Hans Wennborg <hans at chromium.org> wrote:
> > Should this be merged to 3.9?
> >
> > Thanks,
> > Hans
> >
> > On Wed, Jul 27, 2016 at 11:25 AM, Erik Pilkington via cfe-commits
> > <cfe-commits at lists.llvm.org> wrote:
> >> Author: epilk
> >> Date: Wed Jul 27 13:25:10 2016
> >> New Revision: 276900
> >>
> >> URL: http://llvm.org/viewvc/llvm-project?rev=276900&view=rev
> >> Log:
> >> [Sema] Teach getCurrentThisType to reconize lambda in in-class
> initializer
> >>
> >> Fixes PR27994, a crash on valid.
> >>
> >> Differential revision: https://reviews.llvm.org/D21145
> >>
> >> Modified:
> >>     cfe/trunk/lib/Sema/SemaExprCXX.cpp
> >>     cfe/trunk/test/SemaCXX/lambda-expressions.cpp
> >>
> >> Modified: cfe/trunk/lib/Sema/SemaExprCXX.cpp
> >> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/
> SemaExprCXX.cpp?rev=276900&r1=276899&r2=276900&view=diff
> >> ============================================================
> ==================
> >> --- cfe/trunk/lib/Sema/SemaExprCXX.cpp (original)
> >> +++ cfe/trunk/lib/Sema/SemaExprCXX.cpp Wed Jul 27 13:25:10 2016
> >> @@ -961,32 +961,26 @@ static QualType adjustCVQualifiersForCXX
> >>  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()) {
> >> +
> >> +    assert(isa<CXXRecordDecl>(DC) &&
> >> +           "Trying to get 'this' type from static method?");
> >> +
> >> +    // 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.
>

This is wrong in C++17 onwards: if *this is captured by value by a
non-mutable lambda, it should become const-qualified.


> >> +    ThisTy = Context.getPointerType(ClassTy);
> >>    }
> >>
> >>    // If we are within a lambda's call operator, the cv-qualifiers of
> 'this'
> >>
> >> Modified: cfe/trunk/test/SemaCXX/lambda-expressions.cpp
> >> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/
> SemaCXX/lambda-expressions.cpp?rev=276900&r1=276899&r2=276900&view=diff
> >> ============================================================
> ==================
> >> --- cfe/trunk/test/SemaCXX/lambda-expressions.cpp (original)
> >> +++ cfe/trunk/test/SemaCXX/lambda-expressions.cpp Wed Jul 27 13:25:10
> 2016
> >> @@ -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 @@ void foo() {
> >>    };
> >>  }
> >>  }
> >> +
> >> +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;
> >> +}
> >> +}
> >>
> >>
> >> _______________________________________________
> >> cfe-commits mailing list
> >> cfe-commits at lists.llvm.org
> >> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20160811/07685139/attachment-0001.html>