fix Issue 18644 - [dip1000] escape of outer local not detected

src/dmd/escape.d

@@ -1273,6 +1273,19 @@ private void escapeByValue(Expression e, EscapeByResults* er)
                 if (tf.isreturn)
                     e.e1.accept(this);
             }
+
+            /* If it's a nested function that is 'return scope'
+             */
+            if (e.e1.op == TOK.variable)
+            {
+                VarExp ve = cast(VarExp)e.e1;
+                FuncDeclaration fd = ve.var.isFuncDeclaration();
+                if (fd && fd.isNested())
+                {
+                    if (tf.isreturn && tf.isscope)
+                        er.byexp.push(e);
+                }
+            }
         }
     }
 
@@ -1480,6 +1493,19 @@ private void escapeByRef(Expression e, EscapeByResults* er)
                 {
                     escapeByValue(e.e1, er);
                 }
+
+                /* If it's a nested function that is 'return ref'
+                 */
+                if (e.e1.op == TOK.variable)
+                {
+                    VarExp ve = cast(VarExp)e.e1;
+                    FuncDeclaration fd = ve.var.isFuncDeclaration();
+                    if (fd && fd.isNested())
+                    {
+                        if (tf.isreturn)
+                            er.byexp.push(e);
+                    }
+                }
             }
             else
                 er.byexp.push(e);

test/fail_compilation/test18644.d

@@ -0,0 +1,25 @@
+/* REQUIRED_ARGS: -dip1000
+TEST_OUTPUT:
+---
+fail_compilation/test18644.d(15): Error: storing reference to stack allocated value returned by `foo()` into allocated memory causes it to escape
+fail_compilation/test18644.d(16): Error: escaping reference to stack allocated value returned by `foo()`
+fail_compilation/test18644.d(22): Error: escaping reference to stack allocated value returned by `foo()`
+---
+*/
+
+// https://issues.dlang.org/show_bug.cgi?id=18644
+
+@safe int* test1() {
+    int i;
+    int* foo() { return &i; }
+    int*[] b = [foo()];
+    return foo();
+}
+
+@safe ref int test2() {
+    int i;
+    ref int foo() { return i; }
+    return foo();
+}
+
+