Merge fix: Revert to needsClosure() in gen/nested.cpp

As `FuncDeclaration.requiresClosure` appears not to be computed in
all cases yet - this fixes a std.algorithm.iteration unittest
regression.

Author: kinke

dmd/cxxfrontend.d

@@ -439,6 +439,12 @@ PURE isPure(FuncDeclaration fd)
     return dmd.funcsem.isPure(fd);
 }
 
+bool needsClosure(FuncDeclaration fd)
+{
+    import dmd.funcsem;
+    return dmd.funcsem.needsClosure(fd);
+}
+
 /***********************************************************
  * hdrgen.d
  */

dmd/declaration.h

@@ -37,6 +37,7 @@ namespace dmd
     bool checkClosure(FuncDeclaration* fd);
     MATCH leastAsSpecialized(FuncDeclaration *f, FuncDeclaration *g, ArgumentLabels *names);
     PURE isPure(FuncDeclaration *f);
+    bool needsClosure(FuncDeclaration *fd);
     FuncDeclaration *genCfunc(Parameters *args, Type *treturn, const char *name, StorageClass stc=0);
     FuncDeclaration *genCfunc(Parameters *args, Type *treturn, Identifier *id, StorageClass stc=0);
     bool isAbstract(ClassDeclaration *cd);

gen/nested.cpp

@@ -32,7 +32,7 @@ unsigned getVthisIdx(AggregateDeclaration *ad) {
 
 bool isNRVOVar(VarDeclaration *vd) {
   if (auto fd = vd->toParent2()->isFuncDeclaration())
-    return fd->isNRVO() && vd == fd->nrvo_var && !fd->requiresClosure;
+    return fd->isNRVO() && vd == fd->nrvo_var && !dmd::needsClosure(fd);
   return false;
 }
 
@@ -487,7 +487,7 @@ void DtoCreateNestedContext(FuncGenState &funcGen) {
 
     // Create frame for current function and append to frames list
     LLValue *frame = nullptr;
-    bool needsClosure = fd->requiresClosure;
+    bool needsClosure = dmd::needsClosure(fd);
     IF_LOG Logger::println("Needs closure (GC) flag: %d", (int)needsClosure);
     if (needsClosure) {
       LLFunction *fn =