fix Issue 15703 - @safe code should not allow certain types of array …

…casts

src/expression.d

@@ -11329,7 +11329,9 @@ extern (C++) final class CastExp : UnaExp
 
             if (tob.ty == Tarray && t1b.ty == Tsarray) // Bugzilla 12502
                 t1b = t1b.nextOf().arrayOf();
-            if (tob.ty == Tarray && t1b.ty == Tarray)
+
+            if (tob.ty == Tarray   && t1b.ty == Tarray ||
+                tob.ty == Tpointer && t1b.ty == Tpointer)
             {
                 Type tobn = tob.nextOf().toBasetype();
                 Type t1bn = t1b.nextOf().toBasetype();
@@ -11341,31 +11343,25 @@ extern (C++) final class CastExp : UnaExp
                  *  ai[0] = 7;
                  *  *api[0] crash!
                  */
-                if (t1bn.ty == Tvoid && tobn.isMutable() && ex.op != TOKarrayliteral)
+                if (t1bn.ty == Tvoid && tobn.isMutable() &&
+                    !(tob.ty == Tarray && ex.op == TOKarrayliteral))
                     goto Lunsafe;
 
-                if (!tobn.hasPointers() && MODimplicitConv(t1bn.mod, tobn.mod))
-                    goto Lsafe;
-            }
-            if (tob.ty == Tpointer && t1b.ty == Tpointer)
-            {
-                Type tobn = tob.nextOf().toBasetype();
-                Type t1bn = t1b.nextOf().toBasetype();
+                // If the struct is opaque we don't know about the struct members then the cast becomes unsafe
+                if (tobn.ty == Tstruct && !(cast(TypeStruct)tobn).sym.members ||
+                    t1bn.ty == Tstruct && !(cast(TypeStruct)t1bn).sym.members)
+                    goto Lunsafe;
 
-                /* From void* to anything mutable is unsafe because:
-                 *  int** ppi;
-                 *  void* pv = ppi;
-                 *  int* pi = cast(int*) pv;
-                 *  *pi = 7;
-                 *  **ppi crash!
-                 */
-                if (t1bn.ty == Tvoid && tobn.isMutable())
+                const t1pointers = t1bn.hasPointers();
+                const topointers = tobn.hasPointers();
+
+                if (t1pointers && !topointers && tobn.isMutable())
+                    goto Lunsafe;
+
+                if (!t1pointers && topointers)
                     goto Lunsafe;
 
-                // If the struct is opaque we don't know about the struct members and the cast becomes unsafe
-                bool sfwrd = tobn.ty == Tstruct && !(cast(TypeStruct)tobn).sym.members ||
-                             t1bn.ty == Tstruct && !(cast(TypeStruct)t1bn).sym.members;
-                if (!sfwrd && !tobn.hasPointers() &&
+                if (!topointers &&
                     tobn.ty != Tfunction && t1bn.ty != Tfunction &&
                     tobn.size() <= t1bn.size() &&
                     MODimplicitConv(t1bn.mod, tobn.mod))

test/fail_compilation/test15703.d

@@ -0,0 +1,23 @@
+/*
+REQUIRED_ARGS: -m32
+PERMUTE_ARGS:
+TEST_OUTPUT:
+---
+fail_compilation/test15703.d(17): Error: cast from Object[] to uint[] not allowed in safe code
+fail_compilation/test15703.d(19): Error: cast from object.Object to const(uint)* not allowed in safe code
+fail_compilation/test15703.d(22): Error: cast from uint[] to Object[] not allowed in safe code
+---
+*/
+
+// https://issues.dlang.org/show_bug.cgi?id=15703
+
+void test() @safe
+{
+     auto objs = [ new Object() ];
+     auto longs = cast(size_t[]) objs;          // error
+     auto longc = cast(const(size_t)[]) objs;   // ok
+     auto longp = cast(const(size_t)*) objs[0]; // error
+
+     size_t[] al;
+     objs = cast(Object[]) al;                  // error
+}