[gcc/devel/rust/master] Merge #1121

[gcc/devel/rust/master] Merge #1121

[Thomas Schwinge]

https://gcc.gnu.org/g:4152743451a73591fa60bc52f0b28447ef4a8878

commit 4152743451a73591fa60bc52f0b28447ef4a8878
Merge: 5b14291b54f ad9e185e15f
Author: bors[bot] <26634292+bors[bot]@users.noreply.github.com>
Date:   Tue Apr 19 16:33:48 2022 +0000

    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>

Diff:

 gcc/rust/typecheck/rust-hir-trait-ref.h           |  22 ++-
 gcc/rust/typecheck/rust-hir-trait-resolve.cc      |   4 +-
 gcc/rust/typecheck/rust-hir-type-check-implitem.h | 160 +++++++++++-----------
 gcc/rust/typecheck/rust-hir-type-check-item.h     |  10 +-
 gcc/rust/typecheck/rust-hir-type-check.h          |   4 +-
 gcc/rust/typecheck/rust-substitution-mapper.h     |   9 +-
 gcc/rust/typecheck/rust-tyty-bounds.cc            |  86 ++++++++----
 gcc/rust/typecheck/rust-tyty.cc                   |  18 ++-
 gcc/rust/typecheck/rust-tyty.h                    |  28 ++--
 gcc/testsuite/rust/compile/traits9.rs             |   3 +-
 gcc/testsuite/rust/execute/torture/issue-1120.rs  | 123 +++++++++++++++++
 11 files changed, 332 insertions(+), 135 deletions(-)