Do proper construction when initializing __result

Author: limepoutine

compiler/src/dmd/funcsem.d

@@ -2769,6 +2769,7 @@ void buildResultVar(FuncDeclaration fd, Scope* sc, Type tret)
          * fbody.dsymbolSemantic() running, vresult.type might be modified.
          */
         fd.vresult = new VarDeclaration(loc, tret, Id.result, null);
+        fd.vresult._init = new VoidInitializer(loc); // hdrgen requires _init
         fd.vresult.storage_class |= STC.nodtor | STC.temp;
         if (!fd.isVirtual())
             fd.vresult.storage_class |= STC.const_;

compiler/src/dmd/glue/s2ir.d

@@ -661,22 +661,7 @@ void Statement_toIR(Statement s, ref IRState irs, StmtState* stmtstate)
         {
             // Reference return, so convert to a pointer
             e = toElemDtor(s.exp, irs);
-
-            /* already taken care of for vresult in buildResultVar() and semantic3.d
-             * https://issues.dlang.org/show_bug.cgi?id=19384
-             */
-            if (func.vresult)
-                if (BlitExp be = s.exp.isBlitExp())
-                {
-                     if (VarExp ve = be.e1.isVarExp())
-                     {
-                        if (ve.var == func.vresult)
-                            goto Lskip;
-                     }
-                }
-
             e = addressElem(e, s.exp.type.pointerTo());
-         Lskip:
         }
         else
         {

compiler/src/dmd/semantic3.d

@@ -961,8 +961,10 @@ private extern(C++) final class Semantic3Visitor : Visitor
 
                             /* https://issues.dlang.org/show_bug.cgi?id=10789
                              * If NRVO is not possible, all returned lvalues should call their postblits.
+                             * For functions with a __result variable, postblits will be called later
+                             * during initialization of __result.
                              */
-                            if (!funcdecl.isNRVO)
+                            if (!funcdecl.isNRVO && !funcdecl.vresult)
                                 exp = doCopyOrMove(sc2, exp, f.next, true, true);
 
                             if (tret.hasPointers())
@@ -973,13 +975,11 @@ private extern(C++) final class Semantic3Visitor : Visitor
 
                         if (funcdecl.vresult)
                         {
-                            // Create: return vresult = exp;
-                            if (canElideCopy(exp, funcdecl.vresult.type))
-                                exp = new ConstructExp(rs.loc, funcdecl.vresult, exp);
-                            else
-                                exp = new BlitExp(rs.loc, funcdecl.vresult, exp);
-
+                            // Create: return (vresult = exp, vresult);
+                            exp = new ConstructExp(rs.loc, funcdecl.vresult, exp);
                             exp.type = funcdecl.vresult.type;
+                            exp = Expression.combine(exp, new VarExp(rs.loc, funcdecl.vresult));
+                            exp = exp.expressionSemantic(sc2);
 
                             if (rs.caseDim)
                                 exp = Expression.combine(exp, new IntegerExp(rs.caseDim));

compiler/test/compilable/extra-files/vcg-ast.d.cg

@@ -61,7 +61,7 @@ class C : Object
 		}
 		__require();
 		this.__invariant();
-		__result = 2;
+		__result = 2 , __result;
 		goto __returnLabel;
 		__returnLabel:
 		this.__invariant();