Fix one of the regressions found in revert of concept sugaring

[erichkeane]

Summary

It seems that the sugaring patches had some pretty significant
interdependencies, and at least one issue exists that requires part of
the concept-sugaring patch. I don't believe this to have anything to do
with the increased compile-times that were seen, so hopefully this will
fix our problems without further regressions.

See https://reviews.llvm.org/rG12cb1cb3720de8d164196010123ce1a8901d8122
for discussion.

[Mordante]

FYI I tested this patch with libc++ and as expected it does not fix the libc++ modular build ICE.

[alexfh]

Thanks for preparing this fix! I've verified that it fixes the original reproducer as well.

[erichkeane]

In D142500#4079135, @Mordante wrote:

FYI I tested this patch with libc++ and as expected it does not fix the libc++ modular build ICE.

A man can dream, eh? Thank you for testing it! I'm having troubles getting it reproduced unfortunately.

[Mordante]

In D142500#4079669, @erichkeane wrote:

In D142500#4079135, @Mordante wrote:

FYI I tested this patch with libc++ and as expected it does not fix the libc++ modular build ICE.

A man can dream, eh? Thank you for testing it! I'm having troubles getting it reproduced unfortunately.

Of course you can dream, and it would have been great if it had resolved the issue.

Do you have trouble with libc++ or your hardware?

[erichkeane]

In D142500#4080279, @Mordante wrote:

In D142500#4079669, @erichkeane wrote:

In D142500#4079135, @Mordante wrote:

FYI I tested this patch with libc++ and as expected it does not fix the libc++ modular build ICE.

A man can dream, eh? Thank you for testing it! I'm having troubles getting it reproduced unfortunately.

Of course you can dream, and it would have been great if it had resolved the issue.

Do you have trouble with libc++ or your hardware?

I was having trouble with libc++ and the config. The cmake you'd given me was either used poorly, or just didn't work. However, I was able to reproduce it with just the zip file you gave me.

[erichkeane]

In D142500#4080302, @erichkeane wrote:

In D142500#4080279, @Mordante wrote:

In D142500#4079669, @erichkeane wrote:

In D142500#4079135, @Mordante wrote:

FYI I tested this patch with libc++ and as expected it does not fix the libc++ modular build ICE.

A man can dream, eh? Thank you for testing it! I'm having troubles getting it reproduced unfortunately.

Of course you can dream, and it would have been great if it had resolved the issue.

Do you have trouble with libc++ or your hardware?

I was having trouble with libc++ and the config. The cmake you'd given me was either used poorly, or just didn't work. However, I was able to reproduce it with just the zip file you gave me.

Woops, it wasn't you :) It was @mstorsjo who gave me the zip file I can repro from :)

[Mordante]

In D142500#4080317, @erichkeane wrote:

In D142500#4080302, @erichkeane wrote:

In D142500#4080279, @Mordante wrote:

In D142500#4079669, @erichkeane wrote:

In D142500#4079135, @Mordante wrote:

FYI I tested this patch with libc++ and as expected it does not fix the libc++ modular build ICE.

A man can dream, eh? Thank you for testing it! I'm having troubles getting it reproduced unfortunately.

Of course you can dream, and it would have been great if it had resolved the issue.

Do you have trouble with libc++ or your hardware?

I was having trouble with libc++ and the config. The cmake you'd given me was either used poorly, or just didn't work.

:-(

However, I was able to reproduce it with just the zip file you gave me.

Woops, it wasn't you :) It was @mstorsjo who gave me the zip file I can repro from :)

That's great!

clang/lib/Sema/SemaExprCXX.cpp

Sema::BuildCXXTypeConstructExpr(TypeSourceInfo *TInfo,
 
   // C++1z [expr.type.conv]p1:
   //   If the type is a placeholder for a deduced class type, [...perform class
   //   template argument deduction...]
   // C++2b:
   //   Otherwise, if the type contains a placeholder type, it is replaced by the
   //   type determined by placeholder type deduction.
   DeducedType *Deduced = Ty->getContainedDeducedType();
-  if (Deduced && isa<DeducedTemplateSpecializationType>(Deduced)) {
+  if (Deduced && !Deduced->isDeduced() &&
+      isa<DeducedTemplateSpecializationType>(Deduced)) {
     Ty = DeduceTemplateSpecializationFromInitializer(TInfo, Entity,
                                                      Kind, Exprs);
     if (Ty.isNull())
       return ExprError();
     Entity = InitializedEntity::InitializeTemporary(TInfo, Ty);
-  } else if (Deduced) {
+  } else if (Deduced && !Deduced->isDeduced()) {
     MultiExprArg Inits = Exprs;
     if (ListInitialization) {
       auto *ILE = cast<InitListExpr>(Exprs[0]);
       Inits = MultiExprArg(ILE->getInits(), ILE->getNumInits());
     }
 
     if (Inits.empty())
       return ExprError(Diag(TyBeginLoc, diag::err_auto_expr_init_no_expression)
InitializationKind Kind
                         TypeRange.getBegin(), Initializer->getBeginLoc(),
                         Initializer->getEndLoc())
                   : InitializationKind::CreateDirect(TypeRange.getBegin(),
                                                      DirectInitRange.getBegin(),
                                                      DirectInitRange.getEnd());
 
   // C++11 [dcl.spec.auto]p6. Deduce the type which 'auto' stands in for.
   auto *Deduced = AllocType->getContainedDeducedType();
-  if (Deduced && isa<DeducedTemplateSpecializationType>(Deduced)) {
+  if (Deduced && !Deduced->isDeduced() &&
+      isa<DeducedTemplateSpecializationType>(Deduced)) {
     if (ArraySize)
       return ExprError(
           Diag(*ArraySize ? (*ArraySize)->getExprLoc() : TypeRange.getBegin(),
                diag::err_deduced_class_template_compound_type)
           << /*array*/ 2
           << (*ArraySize ? (*ArraySize)->getSourceRange() : TypeRange));
 
     InitializedEntity Entity
       = InitializedEntity::InitializeNew(StartLoc, AllocType);
     AllocType = DeduceTemplateSpecializationFromInitializer(
         AllocTypeInfo, Entity, Kind, Exprs);
     if (AllocType.isNull())
       return ExprError();
-  } else if (Deduced) {
+  } else if (Deduced && !Deduced->isDeduced()) {
     MultiExprArg Inits = Exprs;
     bool Braced = (initStyle == CXXNewExpr::ListInit);
     if (Braced) {
       auto *ILE = cast<InitListExpr>(Exprs[0]);
       Inits = MultiExprArg(ILE->getInits(), ILE->getNumInits());
     }
 
     if (initStyle == CXXNewExpr::NoInit || Inits.empty())

clang/test/SemaTemplate/sugar-crashes.cpp

+// RUN: %clang_cc1 -verify %s
+// expected-no-diagnostics
+
+
+struct StringPiece {
+  template <typename T,
+           typename = decltype(T())>
+             StringPiece(T str) {}
+};
+
+void f(StringPiece utf8) {}
+
+struct S {
+};
+
+void G() {
+  const auto s = S{};
+  StringPiece U{s};
+}
+