Defer creating fields for captures until we finish building the

capturing expression or statement.

No functionality change yet. The intent is that we will also delay
building the initialization expression until the enclosing context, so
that:
a) we build the initialization expression in the right context, and
b) we can elide captures that are not odr-used, as suggested by P0588R1.

This also consolidates some duplicated code building capture fields into
a single place.

llvm-svn: 361893

1 files changed, 55 insertions, 15 deletions

diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp
index f6c9dee2a08..6d487cc8325 100644
--- a/clang/lib/Sema/SemaLambda.cpp
+++ b/clang/lib/Sema/SemaLambda.cpp
@@ -843,19 +843,10 @@ VarDecl *Sema::createLambdaInitCaptureVarDecl(SourceLocation Loc,
   return NewVD;
 }
 
-FieldDecl *Sema::buildInitCaptureField(LambdaScopeInfo *LSI, VarDecl *Var) {
-  FieldDecl *Field = FieldDecl::Create(
-      Context, LSI->Lambda, Var->getLocation(), Var->getLocation(),
-      nullptr, Var->getType(), Var->getTypeSourceInfo(), nullptr, false,
-      ICIS_NoInit);
-  Field->setImplicit(true);
-  Field->setAccess(AS_private);
-  LSI->Lambda->addDecl(Field);
-
+void Sema::addInitCapture(LambdaScopeInfo *LSI, VarDecl *Var) {
   LSI->addCapture(Var, /*isBlock*/false, Var->getType()->isReferenceType(),
                   /*isNested*/false, Var->getLocation(), SourceLocation(),
                   Var->getType(), Var->getInit(), /*Invalid*/false);
-  return Field;
 }
 
 void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
@@ -1182,7 +1173,7 @@ void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
     }
 
     if (C->Init.isUsable()) {
-      buildInitCaptureField(LSI, Var);
+      addInitCapture(LSI, Var);
     } else {
       TryCaptureKind Kind = C->Kind == LCK_ByRef ? TryCapture_ExplicitByRef :
                                                    TryCapture_ExplicitByVal;
@@ -1539,6 +1530,54 @@ bool Sema::DiagnoseUnusedLambdaCapture(SourceRange CaptureRange,
   return true;
 }
 
+/// Create a field within the lambda class or captured statement record for the
+/// given capture.
+FieldDecl *Sema::BuildCaptureField(RecordDecl *RD,
+                                   const sema::Capture &Capture) {
+  SourceLocation Loc = Capture.getLocation();
+  QualType FieldType = Capture.getCaptureType();
+
+  TypeSourceInfo *TSI = nullptr;
+  if (Capture.isVariableCapture()) {
+    auto *Var = Capture.getVariable();
+    if (Var->isInitCapture())
+      TSI = Capture.getVariable()->getTypeSourceInfo();
+  }
+
+  // FIXME: Should we really be doing this? A null TypeSourceInfo seems more
+  // appropriate, at least for an implicit capture.
+  if (!TSI)
+    TSI = Context.getTrivialTypeSourceInfo(FieldType, Loc);
+
+  // Build the non-static data member.
+  FieldDecl *Field =
+      FieldDecl::Create(Context, RD, Loc, Loc, nullptr, FieldType, TSI, nullptr,
+                        false, ICIS_NoInit);
+  // If the variable being captured has an invalid type, mark the class as
+  // invalid as well.
+  if (!FieldType->isDependentType()) {
+    if (RequireCompleteType(Loc, FieldType, diag::err_field_incomplete)) {
+      RD->setInvalidDecl();
+      Field->setInvalidDecl();
+    } else {
+      NamedDecl *Def;
+      FieldType->isIncompleteType(&Def);
+      if (Def && Def->isInvalidDecl()) {
+        RD->setInvalidDecl();
+        Field->setInvalidDecl();
+      }
+    }
+  }
+  Field->setImplicit(true);
+  Field->setAccess(AS_private);
+  RD->addDecl(Field);
+
+  if (Capture.isVLATypeCapture())
+    Field->setCapturedVLAType(Capture.getCapturedVLAType());
+
+  return Field;
+}
+
 ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
                                  LambdaScopeInfo *LSI) {
   // Collect information from the lambda scope.
@@ -1576,14 +1615,12 @@ ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
 
     PopExpressionEvaluationContext();
 
-    // Translate captures.
-    auto CurField = Class->field_begin();
     // True if the current capture has a used capture or default before it.
     bool CurHasPreviousCapture = CaptureDefault != LCD_None;
     SourceLocation PrevCaptureLoc = CurHasPreviousCapture ?
         CaptureDefaultLoc : IntroducerRange.getBegin();
 
-    for (unsigned I = 0, N = LSI->Captures.size(); I != N; ++I, ++CurField) {
+    for (unsigned I = 0, N = LSI->Captures.size(); I != N; ++I) {
       const Capture &From = LSI->Captures[I];
 
       if (From.isInvalid())
@@ -1626,6 +1663,9 @@ ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
         PrevCaptureLoc = CaptureRange.getEnd();
       }
 
+      // Add a FieldDecl for the capture.
+      FieldDecl *Field = BuildCaptureField(Class, From);
+
       // Handle 'this' capture.
       if (From.isThisCapture()) {
         // Capturing 'this' implicitly with a default of '[=]' is deprecated,
@@ -1659,7 +1699,7 @@ ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
       Expr *Init = From.getInitExpr();
       if (!Init) {
         auto InitResult = performLambdaVarCaptureInitialization(
-            *this, From, *CurField, CaptureDefaultLoc, IsImplicit);
+            *this, From, Field, CaptureDefaultLoc, IsImplicit);
         if (InitResult.isInvalid())
           return ExprError();
         Init = InitResult.get();