rfix

src/ddmd/dcast.d

@@ -67,8 +67,8 @@ extern (C++) Expression implicitCastTo(Expression e, Scope* sc, Type t)
         override void visit(Expression e)
         {
             //printf("Expression.implicitCastTo(%s of type %s) => %s\n", e.toChars(), e.type.toChars(), t.toChars());
-
             MATCH match = e.implicitConvTo(t);
+
             if (match)
             {
                 if (match == MATCH.constant && (e.type.constConv(t) || !e.isLvalue() && e.type.equivalent(t)))
@@ -935,6 +935,15 @@ extern (C++) MATCH implicitConvTo(Expression e, Type t)
                     return;
             }
 
+                // Disallow pointer conversions from shared to unshared
+                // Bug https://issues.dlang.org/show_bug.cgi?id=17769
+                // Caused by default = MATCH.constant for visit(CallExp) and default = MATCH.nomatch for visit(Expression)
+                if (e.type.ty == Tpointer && t.ty == Tpointer &&
+                    e.type.nextOf().isShared() && !t.nextOf().isShared())
+                {
+                    return;
+                }
+
             /* Success
              */
             result = MATCH.constant;

test/fail_compilation/fail17769.d

@@ -0,0 +1,27 @@
+/* TEST_OUTPUT:
+---
+fail_compilation/fail17769.d(21): Error: cannot implicitly convert expression `s.method()` of type `shared(int)*` to `int*`
+fail_compilation/fail17769.d(25): Error: cannot implicitly convert expression `foo1` of type `shared(int)*` to `int*`
+fail_compilation/fail17769.d(26): Error: cannot implicitly convert expression `s.ptr` of type `shared(int)*` to `int*`
+---
+*/
+
+// https://issues.dlang.org/show_bug.cgi?id=17769
+
+struct S()
+{
+    shared(int)* method() { return ptr; }
+    shared(int)* ptr;
+}
+
+void main()
+{
+    S!() s;
+    // Correctly rejected - new behaviour
+    int* foo = s.method();
+
+    // Correctly rejected - previous behaviour
+    auto foo1 = s.method();
+    int* bar = foo1; // rejected as expected
+    int* baz = s.ptr; // ditto
+}