Consider v.__ctor() an lvalue

Author: limepoutine

compiler/src/dmd/expressionsem.d

@@ -681,8 +681,19 @@ bool isLvalue(Expression _this)
         if (tf && tf.isRef)
         {
             if (auto dve = _this.e1.isDotVarExp())
+            {
                 if (dve.var.isCtorDeclaration())
-                    return false;
+                {
+                    // Allow taking the address of explicit constructor calls,
+                    // but not (__stmp = S(), __stmp).__ctor().
+
+                    auto ve = lastComma(dve.e1).isVarExp();
+                    if (ve && (ve.var.storage_class & STC.temp) != 0)
+                        return false;
+
+                    return isLvalue(dve.e1);
+                }
+            }
             return true; // function returns a reference
         }
         return false;
@@ -775,8 +786,19 @@ bool canElideCopy(Expression e, Type to, bool checkMod = false)
     static bool visitCallExp(CallExp e)
     {
         if (auto dve = e.e1.isDotVarExp())
+        {
             if (dve.var.isCtorDeclaration())
-                return true;
+            {
+                // Allow (__stmp = S(), __stmp).__ctor() to be elided,
+                // but force a copy for (s2 = s1.__ctor()).
+
+                auto ve = lastComma(dve.e1).isVarExp();
+                if (ve && (ve.var.storage_class & STC.temp) != 0)
+                    return true;
+
+                return canElideCopy(dve.e1, e.type);
+            }
+        }
 
         auto tb = e.e1.type.toBasetype();
         if (tb.ty == Tdelegate || tb.ty == Tpointer)

compiler/test/runnable/rvalue1.d

@@ -284,19 +284,23 @@ struct S12{
 
 struct V12
 {
-    S12 s;
-    this(int) { s = S12(1); }
+    S12 a, b;
+    this(int) { a = b = S12(1); }
 }
 
 S12 foo12()
 {
-    return __rvalue(V12(1).s);
+    return __rvalue(V12(1).a);
 }
 
 void test12()
 {
     S12 s = foo12();
     assert(&s == s.ptr);
+
+    V12 v = V12(1);
+    assert(&v.a == v.a.ptr);
+    assert(&v.b == v.b.ptr);
 }
 
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