fix Issue 17927 - [scope] parameter value can be escaped via return

test/fail_compilation/fail17927.d

@@ -0,0 +1,24 @@
+/* REQUIRED_ARGS: -dip1000
+ * TEST_OUTPUT:
+---
+fail_compilation/fail17927.d(13): Error: scope variable `this` may not be returned
+fail_compilation/fail17927.d(21): Error: scope variable `ptr` may not be returned
+fail_compilation/fail17927.d(23): Error: scope variable `ptr` may not be returned
+---
+*/
+
+// https://issues.dlang.org/show_bug.cgi?id=17927
+
+struct String {
+    const(char)* mem1() const scope @safe { return ptr; }
+
+    inout(char)* mem2() inout scope @safe { return ptr; } // no error because `ref inout` implies `return`
+
+    char* ptr;
+}
+
+
+const(char)* foo1(scope const(char)* ptr) @safe { return ptr; }
+
+inout(char)* foo2(scope inout(char)* ptr) @safe { return ptr; }
+