PR42104: Support instantiations of lambdas that implicitly capture

packs.

Two changes:
 * Track odr-use via FunctionParmPackExprs to properly handle dependent
   odr-uses of packs in generic lambdas.
 * Do not instantiate implicit captures; instead, regenerate them by
   instantiating the body of the lambda. This is necessary to
   distinguish between cases where only one element of a pack is
   captured and cases where the entire pack is captured.

This reinstates r362358 (reverted in r362375) with a fix for an
uninitialized variable use in UpdateMarkingForLValueToRValue.

llvm-svn: 362531

1 files changed, 14 insertions, 14 deletions

diff --git a/clang/lib/Sema/ScopeInfo.cpp b/clang/lib/Sema/ScopeInfo.cpp
index e84e592a482..b2a26af9b4a 100644
--- a/clang/lib/Sema/ScopeInfo.cpp
+++ b/clang/lib/Sema/ScopeInfo.cpp
@@ -229,20 +229,20 @@ bool CapturingScopeInfo::isVLATypeCaptured(const VariableArrayType *VAT) const {
   return false;
 }
 
-void LambdaScopeInfo::getPotentialVariableCapture(unsigned Idx, VarDecl *&VD,
-                                                  Expr *&E) const {
-  assert(Idx < getNumPotentialVariableCaptures() &&
-         "Index of potential capture must be within 0 to less than the "
-         "number of captures!");
-  E = PotentiallyCapturingExprs[Idx];
-  if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
-    VD = dyn_cast<VarDecl>(DRE->getFoundDecl());
-  else if (MemberExpr *ME = dyn_cast<MemberExpr>(E))
-    VD = dyn_cast<VarDecl>(ME->getMemberDecl());
-  else
-    llvm_unreachable("Only DeclRefExprs or MemberExprs should be added for "
-    "potential captures");
-  assert(VD);
+void LambdaScopeInfo::visitPotentialCaptures(
+    llvm::function_ref<void(VarDecl *, Expr *)> Callback) const {
+  for (Expr *E : PotentiallyCapturingExprs) {
+    if (auto *DRE = dyn_cast<DeclRefExpr>(E)) {
+      Callback(cast<VarDecl>(DRE->getFoundDecl()), E);
+    } else if (auto *ME = dyn_cast<MemberExpr>(E)) {
+      Callback(cast<VarDecl>(ME->getMemberDecl()), E);
+    } else if (auto *FP = dyn_cast<FunctionParmPackExpr>(E)) {
+      for (VarDecl *VD : *FP)
+        Callback(VD, E);
+    } else {
+      llvm_unreachable("unexpected expression in potential captures list");
+    }
+  }
 }
 
 FunctionScopeInfo::~FunctionScopeInfo() { }