// capturing lamdbda's call operator.
//
- // The issue is that we cannot rely entirely on the FunctionScopeInfo stack
- // since ScopeInfos are pushed on during parsing and treetransforming. But
- // since a generic lambda's call operator can be instantiated anywhere (even
- // end of the TU) we need to be able to examine its enclosing lambdas and so
- // we use the DeclContext to get a hold of the closure-class and query it for
- // capture information. The reason we don't just resort to always using the
- // DeclContext chain is that it is only mature for lambda expressions
- // enclosing generic lambda's call operators that are being instantiated.
+ // Since the FunctionScopeInfo stack is representative of the lexical
+ // nesting of the lambda expressions during initial parsing (and is the best
+ // place for querying information about captures about lambdas that are
+ // partially processed) and perhaps during instantiation of function templates
+ // that contain lambda expressions that need to be transformed BUT not
+ // necessarily during instantiation of a nested generic lambda's function call
+ // operator (which might even be instantiated at the end of the TU) - at which
+ // time the DeclContext tree is mature enough to query capture information
+ // reliably - we use a two pronged approach to walk through all the lexically
+ // enclosing lambda expressions:
+ //
+ // 1) Climb down the FunctionScopeInfo stack as long as each item represents
+ // a Lambda (i.e. LambdaScopeInfo) AND each LSI's 'closure-type' is lexically
+ // enclosed by the call-operator of the LSI below it on the stack (while
+ // tracking the enclosing DC for step 2 if needed). Note the topmost LSI on
+ // the stack represents the innermost lambda.
+ //
+ // 2) Iterate out through the DeclContext chain (if it represents a lambda's
+ // call operator, and therefore must be a generic lambda's call operator,
+ // which is the only time an inconsistency between the LSI and the
+ // DeclContext should occur) querying closure types regarding capture
+ // information.
+
+ // 1) Climb down the function scope info stack.
for (int I = FunctionScopes.size();
- I-- && isa<LambdaScopeInfo>(FunctionScopes[I]);
+ I-- && isa<LambdaScopeInfo>(FunctionScopes[I]) &&
+ (!CurLSI || CurLSI->Lambda->getDeclContext() ==
+ cast<LambdaScopeInfo>(FunctionScopes[I])->CallOperator);
CurDC = getLambdaAwareParentOfDeclContext(CurDC)) {
CurLSI = cast<LambdaScopeInfo>(FunctionScopes[I]);
return ASTCtx.getPointerType(ClassType);
}
}
- // We've run out of ScopeInfos but check if CurDC is a lambda (which can
- // happen during instantiation of generic lambdas)
+
+ // 2) We've run out of ScopeInfos but check if CurDC is a lambda (which can
+ // happen during instantiation of its nested generic lambda call operator)
if (isLambdaCallOperator(CurDC)) {
- assert(CurLSI);
- assert(isGenericLambdaCallOperatorSpecialization(CurLSI->CallOperator));
+ assert(CurLSI && "While computing 'this' capture-type for a generic "
+ "lambda, we must have a corresponding LambdaScopeInfo");
+ assert(isGenericLambdaCallOperatorSpecialization(CurLSI->CallOperator) &&
+ "While computing 'this' capture-type for a generic lambda, when we "
+ "run out of enclosing LSI's, yet the enclosing DC is a "
+ "lambda-call-operator we must be (i.e. Current LSI) in a generic "
+ "lambda call oeprator");
assert(CurDC == getLambdaAwareParentOfDeclContext(CurLSI->CallOperator));
auto IsThisCaptured =