Bug 7801 – Nested function returning garbage instead of closed-over parameter

I ran into a strange and hard-to-describe problem with nested functions closing over the argument to their enclosing function. When a nested function (A) returns the value of another nested function (B) that returns a parameter of the enclosing function (C), and when (A) is returned from (C), then calling (A) returns an incorrect value if either run from a 32-bit program, or run from 64-bit and (A) has a parameter of class type (it works when (A) has no class parameters). The following code demonstrates the issue: auto foo(T)(int val) { int nested() { return val; } int escaping(T ignored) { return nested(); } return &escaping; } struct Bar {} class Baz {} void main() { auto func1 = foo!int(55); auto val1 = func1(12); // 64-bit ok, 32-bit fail (varying) assert(val1 == 55); auto func2 = foo!Bar(55); Bar bar; auto val2 = func2(bar); // 64-bit ok, 32-bit fail (equal to incorrect val1) assert(val2 == 55); auto func3 = foo!Baz(55); auto baz = new Baz(); auto val3 = func3(baz); // 64- and 32-bit fail (varying, different from val1/val2) assert(val3 == 55); }

*** This issue has been marked as a duplicate of issue 1841 ***