[PATCH] D114207: [clang] fix regression deducing pack expansion arguments introduced by D110216

Thu Nov 18 18:36:29 PST 2021

This revision was not accepted when it landed; it landed in state "Needs Review".
This revision was automatically updated to reflect the committed changes.
Closed by commit rG85914b757015: [clang] fix regression deducing pack expansion arguments introduced by D110216 (authored by mizvekov).

Changed prior to commit:
  https://reviews.llvm.org/D114207?vs=388351&id=388362#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D114207/new/

https://reviews.llvm.org/D114207

Files:
  clang/lib/Sema/SemaTemplateDeduction.cpp
  clang/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.partial/p12.cpp


Index: clang/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.partial/p12.cpp
===================================================================

--- clang/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.partial/p12.cpp
+++ clang/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.partial/p12.cpp
@@ -1,5 +1,4 @@
 // RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s
-// expected-no-diagnostics
 
 // Note: Partial ordering of function templates containing template
 // parameter packs is independent of the number of deduced arguments
@@ -26,3 +25,15 @@
   double &dr1 = h((int(*)(int, float&))0);
   double &dr2 = h((int(*)(int))0);
 }
+
+namespace test_j {
+
+template <int I> struct ref {};
+
+template <int... L> void map(ref<L>...);
+template <int head, int... tail> void map(ref<head> x, ref<tail>... xs); // expected-note {{here}}
+
+template void map<0, 1>(ref<0>, ref<1>);
+// expected-error at -1 {{explicit instantiation of undefined function template 'map'}}
+
+} // namespace test_j
Index: clang/lib/Sema/SemaTemplateDeduction.cpp
===================================================================
--- clang/lib/Sema/SemaTemplateDeduction.cpp
+++ clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -1337,6 +1337,13 @@
     TemplateDeductionInfo &Info,
     SmallVectorImpl<DeducedTemplateArgument> &Deduced, unsigned TDF,
     bool PartialOrdering, bool DeducedFromArrayBound) {
+
+  // If the argument type is a pack expansion, look at its pattern.
+  // This isn't explicitly called out
+  if (const auto *AExp = dyn_cast<PackExpansionType>(A))
+    A = AExp->getPattern();
+  assert(!isa<PackExpansionType>(A.getCanonicalType()));
+
   if (PartialOrdering) {
     // C++11 [temp.deduct.partial]p5:
     //   Before the partial ordering is done, certain transformations are


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