[PATCH] [C++11] Support for capturing of variable length arrays in lambda expression.

[Richard Smith]

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Comment at: lib/AST/Decl.cpp:3265
@@ +3264,3 @@
+      InitializerOrBitWidth.getPointer()) {
+    if (getDeclContext() && getDeclContext()->isRecord()) {
+      if (auto *RD = dyn_cast<CXXRecordDecl>(getParent())) {
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You don't need the `isRecord` check here, and you shouldn't need the `getDeclContext` check either. If some buggy code is querying this when there is no `DeclContext`, it'd be better to crash or assert because you cannot give a correct answer.

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Comment at: lib/AST/Decl.cpp:3309
@@ -3295,3 +3308,3 @@
   InitializerOrBitWidth.setPointer(Width);
 }
 
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Please `assert(isBitField())` or similar here to ensure that we don't set a bit width on a lambda capture.

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Comment at: lib/AST/Decl.cpp:3328-3329
@@ +3327,4 @@
+void FieldDecl::setCapturedVLABoundExpr(Expr *CapturedExpr) {
+  assert(isa<CXXRecordDecl>(getParent()) &&
+         cast<CXXRecordDecl>(getParent())->isLambda() &&
+         "capturing expression in non-lambda.");
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Given the number of times you do this `isa<CXXRecordDecl> && isLambda` check, I'd prefer for you to add an `isLambda` member to `RecordDecl` and have it do the `dyn_cast` to `CXXRecordDecl`.

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Comment at: lib/Sema/SemaExpr.cpp:12220-12235
@@ +12219,18 @@
+            if (auto LSI = dyn_cast<LambdaScopeInfo>(CSI)) {
+              auto Loc = Size->getExprLoc();
+              auto QType = Size->getType();
+              auto QArrayType = QualType(Vat, 0);
+              auto TInfo = Context.getTrivialTypeSourceInfo(QType, Loc);
+              auto QArrayTInfo =
+                  Context.getTrivialTypeSourceInfo(QArrayType, Loc);
+              auto VD = VarDecl::Create(Context, getFunctionLevelDeclContext(),
+                                        SourceLocation(), SourceLocation(),
+                                        &Context.Idents.get(".captured_expr."),
+                                        QArrayType, QArrayTInfo, SC_Auto);
+              auto DRE =
+                  new (Context) DeclRefExpr(VD, /*refersToEnclosingLocal*/ true,
+                                            QArrayType, VK_LValue, Loc);
+              auto BinExpr = new (Context) BinaryOperator(
+                  DRE, Size, BO_Comma, QType, Size->getValueKind(), OK_Ordinary,
+                  Loc, /*fpContractable*/ false);
+              auto Lambda = LSI->Lambda;
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This seems like a hack: could you instead make the `FieldDecl` directly store the `VariableArrayType *`, rather than creating a proxy expression and variable to carry it?

http://reviews.llvm.org/D4368