Issue 2486 - taking address of slice rvalue is valid

src/expression.c

@@ -9546,16 +9546,6 @@ void SliceExp::checkEscapeRef()
     e1->checkEscapeRef();
 }
 
-int SliceExp::isLvalue()
-{
-    return 1;
-}
-
-Expression *SliceExp::toLvalue(Scope *sc, Expression *e)
-{
-    return this;
-}
-
 int SliceExp::checkModifiable(Scope *sc, int flag)
 {
     //printf("SliceExp::checkModifiable %s\n", toChars());

src/expression.h

@@ -1131,8 +1131,6 @@ struct SliceExp : UnaExp
     void checkEscape();
     void checkEscapeRef();
     int checkModifiable(Scope *sc, int flag);
-    int isLvalue();
-    Expression *toLvalue(Scope *sc, Expression *e);
     Expression *modifiableLvalue(Scope *sc, Expression *e);
     int isBool(int result);
     void toCBuffer(OutBuffer *buf, HdrGenState *hgs);

src/mtype.c

@@ -5941,29 +5941,28 @@ MATCH TypeFunction::callMatch(Expression *ethis, Expressions *args, int flag)
 
         // Non-lvalues do not match ref or out parameters
         if (p->storageClass & STCref)
-        {   if (m && !arg->isLvalue())
+        {
+            Type *targb = targ->toBasetype();
+            Type *tprmb = tprm->toBasetype();
+            //printf("%s\n", targb->toChars());
+            //printf("%s\n", tprmb->toChars());
+
+            if (m && !arg->isLvalue())
             {
-                Type *ta = targ->aliasthisOf();
-                if (arg->op == TOKstring && tprm->ty == Tsarray)
-                {   if (targ->ty != Tsarray)
-                        targ = new TypeSArray(targ->nextOf(),
+                if (arg->op == TOKstring && tprmb->ty == Tsarray)
+                {   if (targb->ty != Tsarray)
+                        targb = new TypeSArray(targb->nextOf(),
                                 new IntegerExp(0, ((StringExp *)arg)->len,
                                 Type::tindex));
                 }
+                else if (arg->op == TOKslice && tprmb->ty == Tsarray)
+                {   // Allow conversion from T[lwr .. upr] to ref T[upr-lwr]
+                    targb = tprmb;
+                }
                 else
                     goto Nomatch;
             }
 
-            Type *targb = targ->toBasetype();
-            Type *tprmb = tprm->toBasetype();
-            //printf("%s\n", targb->toChars());
-            //printf("%s\n", tprmb->toChars());
-
-            if (arg->op == TOKslice && tprmb->ty == Tsarray)
-            {   // Allow conversion from T[lwr .. upr] to ref T[upr-lwr]
-                targb = tprmb;
-            }
-
             /* find most derived alias this type being matched.
              */
             while (1)

src/template.c

@@ -1592,9 +1592,14 @@ MATCH TemplateDeclaration::deduceFunctionTemplateMatch(Loc loc, Scope *sc, Objec
             }
 
             if (m && (fparam->storageClass & (STCref | STCauto)) == STCref)
-            {   if (!farg->isLvalue())
+            {
+                if (!farg->isLvalue())
                 {
-                    goto Lnomatch;
+                    if (farg->op == TOKslice && argtype->ty == Tsarray)
+                    {   // Allow conversion from T[lwr .. upr] to ref T[upr-lwr]
+                    }
+                    else
+                        goto Lnomatch;
                 }
             }
             if (m && (fparam->storageClass & STCout))

test/compilable/interpret3.d

@@ -1108,7 +1108,8 @@ struct Zadok
     int bfg()
     {
         z[0] = 56;
-        fog(z[]) = [56, 6, 8];
+        auto zs = z[];
+        fog(zs) = [56, 6, 8];
         assert(z[1] == 6);
         assert(z[0] == 56);
         return z[2];

test/runnable/test12.d

@@ -280,26 +280,26 @@ void test11()
 
 struct Array12
 {
-	char len;
-	void* p;
-}
-Array12 f12(string a)
-{
-	return *cast(Array12*) &a[0..23]; //Internal error: ..\ztc\cgcs.c 350
+    char len;
+    void* p;
 }
+//Array12 f12(string a)
+//{
+//    return *cast(Array12*) &a[0..23]; //Internal error: ..\ztc\cgcs.c 350
+//}
 
 Array12 g12(string a)
 {
-	return *cast(Array12*) &a; //works
+    return *cast(Array12*) &a; //works
 }
 
 void test12()
 {
     string a = "12345678901234567890123";
     Array12 b;
 
-    b = f12(a);
-    printf("b.len = %x\n", b.len);
+    //b = f12(a);
+    //printf("b.len = %x\n", b.len);
     b = g12(a);
     printf("b.len = %x\n", b.len);
 }

test/runnable/xtest46.d

@@ -3493,6 +3493,29 @@ void test155()
     b = b >> i;
 }
 
+/***************************************************/
+// 2486
+
+void test2486()
+{
+    void foo(ref int[] arr) {}
+
+    int[] arr = [1,2,3];
+    foo(arr);   //OK
+    static assert(!__traits(compiles, foo(arr[1..2]))); // should be NG
+
+    struct S
+    {
+        int[] a;
+        auto ref opSlice(){ return a[]; }  // line 4
+    }
+    S s;
+    s[];
+    // opSlice should return rvalue
+    static assert(is(typeof(&S.opSlice) == int[] function()));
+    static assert(!__traits(compiles, foo(s[])));       // should be NG
+}
+
 /***************************************************/
 // 2521
 
@@ -5996,6 +6019,7 @@ int main()
     test8442();
     test86();
     test87();
+    test2486();
     test5554();
     test88();
     test7545();