[clang] 68b9d8e - [clang] fix transformation of template arguments of 'auto' type constraints

[Matheus Izvekov via cfe-commits]

Author: Matheus Izvekov
Date: 2021-09-08T03:22:34+02:00
New Revision: 68b9d8ed7abe4046992ae1557990edfbb3a772bc

URL: https://github.com/llvm/llvm-project/commit/68b9d8ed7abe4046992ae1557990edfbb3a772bc
DIFF: https://github.com/llvm/llvm-project/commit/68b9d8ed7abe4046992ae1557990edfbb3a772bc.diff

LOG: [clang] fix transformation of template arguments of 'auto' type constraints

See PR48617.

When assigning the new template arguments to the new TypeLoc, we were looping
on the argument count of the original TypeLoc instead of the new one,
which can be different when packs are present.

Signed-off-by: Matheus Izvekov <mizvekov at gmail.com>

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D109406

Added: 
    

Modified: 
    clang/lib/Sema/TreeTransform.h
    clang/test/CXX/dcl/dcl.spec/dcl.type/dcl.spec.auto/p6.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 8841b2e00d40f..2a7ceaf6425ee 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -6578,7 +6578,7 @@ QualType TreeTransform<Derived>::TransformAutoType(TypeLocBuilder &TLB,
   NewTL.setFoundDecl(TL.getFoundDecl());
   NewTL.setLAngleLoc(TL.getLAngleLoc());
   NewTL.setRAngleLoc(TL.getRAngleLoc());
-  for (unsigned I = 0; I < TL.getNumArgs(); ++I)
+  for (unsigned I = 0; I < NewTL.getNumArgs(); ++I)
     NewTL.setArgLocInfo(I, NewTemplateArgs.arguments()[I].getLocInfo());
 
   return Result;

diff  --git a/clang/test/CXX/dcl/dcl.spec/dcl.type/dcl.spec.auto/p6.cpp b/clang/test/CXX/dcl/dcl.spec/dcl.type/dcl.spec.auto/p6.cpp
index 7830d1f435262..4941027423217 100644
--- a/clang/test/CXX/dcl/dcl.spec/dcl.type/dcl.spec.auto/p6.cpp
+++ b/clang/test/CXX/dcl/dcl.spec/dcl.type/dcl.spec.auto/p6.cpp
@@ -76,3 +76,25 @@ namespace PR48593 {
   template<class> concept d = true;
   d<,> auto e = 0; // expected-error{{expected expression}}
 }
+
+namespace PR48617 {
+  template <typename...> concept C = true;
+  template <typename...> class A {};
+
+  template <typename... Ts> C<Ts...> auto e(A<Ts...>) { return 0; }
+
+  // FIXME: The error here does not make sense.
+  template auto e<>(A<>);
+  // expected-error at -1 {{explicit instantiation of 'e' does not refer to a function template}}
+  // expected-note at -5  {{candidate template ignored: failed template argument deduction}}
+
+  // FIXME: Should be able to instantiate this with no errors.
+  template C<int> auto e<int>(A<int>);
+  // expected-error at -1 {{explicit instantiation of 'e' does not refer to a function template}}
+  // expected-note at -10 {{candidate template ignored: could not match 'C<int, Ts...> auto' against 'C<int> auto'}}
+  
+  template C<> auto e<>(A<>);
+
+  template <typename... Ts> A<Ts...> c(Ts...);
+  int f = e(c(1, 2));
+}