Merge #1121

1121: Fix bad projection substitution r=philberty a=philberty

When we have a Trait such as:

```
pub unsafe trait SliceIndex<T> {
    type Output;

    fn index(self, slice: &T) -> &Self::Output;
}

unsafe impl<T> SliceIndex<[T]> for Range<usize> {
    type Output = [T];

    fn index(self, slice: &[T]) -> &[T] {
        unsafe { &*self.get_unchecked(slice) }
    }
}

```

When we need to verify that the impl index is compatible fir SliceIndex we
get the Type info for the trait-item which is:

  fn<Self, T> index(self: Self, slice: &T)
        -> &<placeholder=projection<T>=[T]>

This projection gets setup and the types are substituted with
Self=Range<usize> and T=[T] which ended up substituting the projection
twice resulting in a recursive slice [T=[T]]. In this case the associated
type is already setup for the placeholder and does not require generic
substitution. This means we added a flag to the substitution generic
arguments mappings to handle this case.

This patch also addressed memory corruption with the TypeBoundPredicate
as part of the debugging of this issue which resulted in a segv when
trying to debug the mappings. The issue was the copy constructors needed
to update the used argument mappings each time since the substitution param
mappings are copied and the addresses no longer exist, valgrind was great
here to find this issue.

Fixes #1120


Co-authored-by: Philip Herron <philip.herron@embecosm.com>

0 files changed, 0 insertions, 0 deletions