Introduce support for template instantiation of lambda
expressions. This is mostly a simple refact, splitting the main "start
a lambda expression" function into smaller chunks that are driven
either from the parser (Sema::ActOnLambdaExpr) or during AST
transformation (TreeTransform::TransformLambdaExpr). A few minor
interesting points:
- Added new entry points for TreeTransform, so that we can
explicitly establish the link between the lambda closure type in the
template and the lambda closure type in the instantiation.
- Added a bit into LambdaExpr specifying whether it had an explicit
result type or not. We should have had this anyway.
This code is 'lightly' tested.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150417 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/TreeTransform.h b/lib/Sema/TreeTransform.h
index 8744f41..ba6ec82 100644
--- a/lib/Sema/TreeTransform.h
+++ b/lib/Sema/TreeTransform.h
@@ -112,6 +112,11 @@
protected:
Sema &SemaRef;
+ /// \brief The set of local declarations that have been transformed, for
+ /// cases where we are forced to build new declarations within the transformer
+ /// rather than in the subclass (e.g., lambda closure types).
+ llvm::DenseMap<Decl *, Decl *> TransformedLocalDecls;
+
public:
/// \brief Initializes a new tree transformer.
TreeTransform(Sema &SemaRef) : SemaRef(SemaRef) { }
@@ -351,10 +356,36 @@
/// \brief Transform the given declaration, which is referenced from a type
/// or expression.
///
- /// By default, acts as the identity function on declarations. Subclasses
+ /// By default, acts as the identity function on declarations, unless the
+ /// transformer has had to transform the declaration itself. Subclasses
/// may override this function to provide alternate behavior.
- Decl *TransformDecl(SourceLocation Loc, Decl *D) { return D; }
+ Decl *TransformDecl(SourceLocation Loc, Decl *D) {
+ llvm::DenseMap<Decl *, Decl *>::iterator Known
+ = TransformedLocalDecls.find(D);
+ if (Known != TransformedLocalDecls.end())
+ return Known->second;
+
+ return D;
+ }
+ /// \brief Transform the attributes associated with the given declaration and
+ /// place them on the new declaration.
+ ///
+ /// By default, this operation does nothing. Subclasses may override this
+ /// behavior to transform attributes.
+ void transformAttrs(Decl *Old, Decl *New) { }
+
+ /// \brief Note that a local declaration has been transformed by this
+ /// transformer.
+ ///
+ /// Local declarations are typically transformed via a call to
+ /// TransformDefinition. However, in some cases (e.g., lambda expressions),
+ /// the transformer itself has to transform the declarations. This routine
+ /// can be overridden by a subclass that keeps track of such mappings.
+ void transformedLocalDecl(Decl *Old, Decl *New) {
+ TransformedLocalDecls[Old] = New;
+ }
+
/// \brief Transform the definition of the given declaration.
///
/// By default, invokes TransformDecl() to transform the declaration.
@@ -7622,8 +7653,109 @@
template<typename Derived>
ExprResult
TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
- assert(false && "Lambda expressions cannot be instantiated (yet)");
- return ExprError();
+ // Create the local class that will describe the lambda.
+ CXXRecordDecl *Class
+ = getSema().createLambdaClosureType(E->getIntroducerRange());
+ getDerived().transformedLocalDecl(E->getLambdaClass(), Class);
+
+ // Transform the type of the lambda parameters and start the definition of
+ // the lambda itself.
+ TypeSourceInfo *MethodTy
+ = TransformType(E->getCallOperator()->getTypeSourceInfo());
+ if (!MethodTy)
+ return ExprError();
+
+ // Build the call operator.
+ CXXMethodDecl *CallOperator
+ = getSema().startLambdaDefinition(Class, E->getIntroducerRange(),
+ MethodTy,
+ E->getCallOperator()->getLocEnd());
+ getDerived().transformAttrs(E->getCallOperator(), CallOperator);
+
+ // Enter the scope of the lambda.
+ sema::LambdaScopeInfo *LSI
+ = getSema().enterLambdaScope(CallOperator, E->getIntroducerRange(),
+ E->getCaptureDefault(),
+ E->hasExplicitParameters(),
+ E->hasExplicitResultType(),
+ E->isMutable());
+
+ // Transform captures.
+ bool Invalid = false;
+ bool FinishedExplicitCaptures = false;
+ for (LambdaExpr::capture_iterator C = E->capture_begin(),
+ CEnd = E->capture_end();
+ C != CEnd; ++C) {
+ // When we hit the first implicit capture, tell Sema that we've finished
+ // the list of explicit captures.
+ if (!FinishedExplicitCaptures && C->isImplicit()) {
+ getSema().finishLambdaExplicitCaptures(LSI);
+ FinishedExplicitCaptures = true;
+ }
+
+ // Capturing 'this' is trivial.
+ if (C->capturesThis()) {
+ getSema().CheckCXXThisCapture(C->getLocation(), C->isExplicit());
+ continue;
+ }
+
+ // Transform the captured variable.
+ VarDecl *CapturedVar
+ = cast_or_null<VarDecl>(getDerived().TransformDecl(C->getLocation(),
+ C->getCapturedVar()));
+ if (!CapturedVar) {
+ Invalid = true;
+ continue;
+ }
+
+ // Capture the transformed variable.
+ getSema().TryCaptureVar(CapturedVar, C->getLocation(),
+ C->isImplicit()? Sema::TryCapture_Implicit
+ : C->getCaptureKind() == LCK_ByCopy
+ ? Sema::TryCapture_ExplicitByVal
+ : Sema::TryCapture_ExplicitByRef);
+ }
+ if (!FinishedExplicitCaptures)
+ getSema().finishLambdaExplicitCaptures(LSI);
+
+ // Transform lambda parameters.
+ llvm::SmallVector<QualType, 4> ParamTypes;
+ llvm::SmallVector<ParmVarDecl *, 4> Params;
+ if (!getDerived().TransformFunctionTypeParams(E->getLocStart(),
+ E->getCallOperator()->param_begin(),
+ E->getCallOperator()->param_size(),
+ 0, ParamTypes, &Params))
+ getSema().addLambdaParameters(CallOperator, /*CurScope=*/0, Params);
+ else
+ Invalid = true;
+
+
+ // Enter a new evaluation context to insulate the lambda from any
+ // cleanups from the enclosing full-expression.
+ getSema().PushExpressionEvaluationContext(Sema::PotentiallyEvaluated);
+
+ if (Invalid) {
+ getSema().ActOnLambdaError(E->getLocStart(), /*CurScope=*/0,
+ /*IsInstantiation=*/true);
+ return ExprError();
+ }
+
+ // Instantiate the body of the lambda expression.
+ StmtResult Body;
+ {
+ Sema::ContextRAII SavedContext(getSema(), CallOperator);
+
+ Body = getDerived().TransformStmt(E->getBody());
+ if (Body.isInvalid()) {
+ getSema().ActOnLambdaError(E->getLocStart(), /*CurScope=*/0,
+ /*IsInstantiation=*/true);
+ return ExprError();
+ }
+ }
+
+ return getSema().ActOnLambdaExpr(E->getLocStart(), Body.take(),
+ /*CurScope=*/0,
+ /*IsInstantiation=*/true);
}
template<typename Derived>