[Clang] Fix dependency computation for pack indexing expression

Given `foo...[idx]` if idx is value dependent, the expression is type dependent. Fixes llvm#91885 Fixes llvm#91884
cor3ntin · May 13, 2024 · 4cadff5 · 4cadff5
1 parent d4f5cf2
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diff --git a/clang/lib/AST/ComputeDependence.cpp b/clang/lib/AST/ComputeDependence.cpp
@@ -376,6 +376,9 @@ ExprDependence clang::computeDependence(PackExpansionExpr *E) {
 
 ExprDependence clang::computeDependence(PackIndexingExpr *E) {
   ExprDependence D = E->getIndexExpr()->getDependence();
+  if (D & ExprDependence::Value)
+    D |= ExprDependence::TypeInstantiation;
+
   ArrayRef<Expr *> Exprs = E->getExpressions();
   if (Exprs.empty())
     D |= (E->getPackIdExpression()->getDependence() |

diff --git a/clang/test/SemaCXX/cxx2c-pack-indexing.cpp b/clang/test/SemaCXX/cxx2c-pack-indexing.cpp
@@ -194,3 +194,17 @@ void h() {
   // expected-note-re@-2 {{function template specialization '{{.*}}' requested here}}
 }
 }
+
+namespace GH91885 {
+
+void test(auto...args){
+    [&]<int idx>(){
+        using R = decltype( args...[idx] ) ;
+    }.template operator()<0>();
+}
+
+void f( ) {
+    test(1);
+}
+
+}