Issue 13756 - [AA] Allow ref const index on foreach AA iteration

src/opover.c

@@ -1644,6 +1644,8 @@ bool inferApplyArgTypes(ForeachStatement *fes, Scope *sc, Dsymbol *&sapply)
                 {
                     arg->type = taa->index;     // key type
                     arg->type = arg->type->addStorageClass(arg->storageClass);
+                    if (arg->storageClass & STCref) // key must not be mutated via ref
+                        arg->type = arg->type->addMod(MODconst);
                 }
                 arg = (*fes->arguments)[1];
             }

src/statement.c

@@ -2326,35 +2326,41 @@ Statement *ForeachStatement::semantic(Scope *sc)
             {
                 // Check types
                 Parameter *arg = (*arguments)[0];
+                bool isRef = (arg->storageClass & STCref) != 0;
+                Type *ta = arg->type;
                 if (dim == 2)
                 {
-                    if (arg->storageClass & STCref)
-                    {
-                        error("foreach: index cannot be ref");
-                        goto Lerror2;
-                    }
-                    if (!taa->index->implicitConvTo(arg->type))
+                    Type *ti = (isRef ? taa->index->addMod(MODconst) : taa->index);
+                    if (isRef ? !ti->constConv(ta) : !ti->implicitConvTo(ta))
                     {
-                        error("foreach: index must be type %s, not %s", taa->index->toChars(), arg->type->toChars());
+                        error("foreach: index must be type %s, not %s", ti->toChars(), ta->toChars());
                         goto Lerror2;
                     }
                     arg = (*arguments)[1];
+                    isRef = (arg->storageClass & STCref) != 0;
+                    ta = arg->type;
                 }
-                if ((!arg->type->equals(taa->nextOf()) && (arg->storageClass & STCref)) ||
-                    !taa->nextOf()->implicitConvTo(arg->type))
+                Type *tn = taa->nextOf();
+                if (isRef ? !tn->constConv(ta) : !tn->implicitConvTo(ta))
                 {
-                    error("foreach: value must be type %s, not %s", taa->nextOf()->toChars(), arg->type->toChars());
+                    error("foreach: value must be type %s, not %s", tn->toChars(), ta->toChars());
                     goto Lerror2;
                 }
+
                 /* Call:
+                 *  extern(C) int _aaApply(void*, in size_t, int delegate(void*))
                  *      _aaApply(aggr, keysize, flde)
+                 *
+                 *  extern(C) int _aaApply2(void*, in size_t, int delegate(void*, void*))
+                 *      _aaApply2(aggr, keysize, flde)
                  */
                 static const char *name[2] = { "_aaApply", "_aaApply2" };
                 static FuncDeclaration *fdapply[2] = { NULL, NULL };
                 static TypeDelegate *fldeTy[2] = { NULL, NULL };
 
-                unsigned char i = dim == 2;
-                if (!fdapply[i]) {
+                unsigned char i = (dim == 2 ? 1 : 0);
+                if (!fdapply[i])
+                {
                     args = new Parameters;
                     args->push(new Parameter(0, Type::tvoid->pointerTo(), NULL, NULL));
                     args->push(new Parameter(STCin, Type::tsize_t, NULL, NULL));
@@ -2373,7 +2379,8 @@ Statement *ForeachStatement::semantic(Scope *sc)
                 size_t keysize = (size_t)taa->index->size();
                 keysize = (keysize + ((size_t)Target::ptrsize-1)) & ~((size_t)Target::ptrsize-1);
                 // paint delegate argument to the type runtime expects
-                if (!fldeTy[i]->equals(flde->type)) {
+                if (!fldeTy[i]->equals(flde->type))
+                {
                     flde = new CastExp(loc, flde, flde->type);
                     flde->type = fldeTy[i];
                 }

test/fail_compilation/fail13756.d

@@ -0,0 +1,14 @@
+/*
+TEST_OUTPUT:
+---
+fail_compilation/fail13756.d(11): Error: foreach: index must be type const(int), not int
+---
+*/
+
+void maiin()
+{
+    int[int] aa = [1:2];
+    foreach (ref int k, v; aa)
+    {
+    }
+}

test/runnable/foreach5.d

@@ -962,6 +962,75 @@ void test12932() @nogc
     assert(sum == 6);
 }
 
+/***************************************/
+// 13756
+
+void test13756()
+{
+    int[int] org = [1:2], aa;
+
+    aa = org.dup;
+    foreach (v; aa)
+    {
+        static assert(is(typeof(v) == int));
+        v = 20;
+    }
+    assert(aa == [1:2]);
+
+    aa = org.dup;
+    foreach (ref v; aa)
+    {
+        static assert(is(typeof(v) == int));
+        v = 20;
+    }
+    assert(aa == [1:20]);
+
+    aa = org.dup;
+    foreach (k, v; aa)
+    {
+        static assert(is(typeof(k) == int));
+        static assert(is(typeof(v) == int));
+        k = 10;
+        v = 20;
+    }
+    assert(aa == [1:2]);
+
+    aa = org.dup;
+    foreach (k, ref v; aa)
+    {
+        static assert(is(typeof(k) == int));
+        static assert(is(typeof(v) == int));
+        k = 10;
+        v = 20;
+    }
+    assert(aa == [1:20]);
+
+    aa = org.dup;
+    foreach (ref k, v; aa)      // NG -> OK
+    {
+        static assert(is(typeof(k) == const int));
+        static assert(is(typeof(v) == int));
+        static assert(!__traits(compiles, k = 10));
+        v = 20;
+    }
+    assert(aa == [1:2]);
+
+    aa = org.dup;
+    foreach (ref k, ref v; aa)  // NG -> OK
+    {
+        static assert(is(typeof(k) == const int));
+        static assert(is(typeof(v) == int));
+        static assert(!__traits(compiles, k = 10));
+        v = 20;
+    }
+    assert(aa == [1:20]);
+
+    foreach (ref const k, v; aa)  // NG -> OK, same with 'ref k'
+    {
+        static assert(is(typeof(k) == const int));
+    }
+}
+
 /***************************************/
 
 int main()
@@ -991,6 +1060,7 @@ int main()
     test12103();
     test12739();
     test12932();
+    test13756();
 
     printf("Success\n");
     return 0;