Changes error message from displaying first found missing constructor witness to showing up to 10, if necessary.

Fixes issue #16884.

This explicitly adds an option telling the linker on these platforms to make the stack and heap non-executable (should already be the case for Windows, and likely OS X).

Without this option there is some risk of accidentally losing NX protection, as the linker will not enable NX if any of the binary's constituent objects don't contain the .note.GNU-stack header.

We're not aware of any users who would want a binary with executable stack or heap, but in future this could be made possible by passing a flag to disable the protection, which would also help document the fact to the crate's users.

Edit: older discussion of previous quickfix to add a .note.GNU-stack header to libunwind's assembly:

Short term solution for issue #30824 to ensure that object files generated from assembler contain the .note.GNU-stack header.

When this header is not present in any constituent object files, the linker refrains from making the stack NX in the final executable.

Further actions:

I'll try to get this change merged in with upstream too, and then update these instructions to just compile the fixed version.

It seems a good idea to use issue #30824 or some other issue to add a test that similar security regressions can be automatically caught in future.

`LateContext` already does this, looks like this was just forgotten in #29850.

Found while investigating #30326 (but doesn't fix it)

This commit removes the `-D warnings` flag being passed through the makefiles to
all crates to instead be a crate attribute. We want these attributes always
applied for all our standard builds, and this is more amenable to Cargo-based
builds as well.

Note that all `deny(warnings)` attributes are gated with a `cfg(stage0)`
attribute currently to match the same semantics we have today

This commit implements the stabilization of the custom hasher support intended
for 1.7 but left out due to some last-minute questions that needed some
decisions. A summary of the actions done in this PR are:

Stable

* `std::hash::BuildHasher`
* `BuildHasher::Hasher`
* `BuildHasher::build_hasher`
* `std::hash::BuildHasherDefault`
* `HashMap::with_hasher`
* `HashMap::with_capacity_and_hasher`
* `HashSet::with_hasher`
* `HashSet::with_capacity_and_hasher`
* `std::collections::hash_map::RandomState`
* `RandomState::new`

Deprecated

* `std::collections::hash_state`
* `std::collections::hash_state::HashState` - this trait was also moved into
  `std::hash` with a reexport here to ensure that we can have a blanket impl to
  prevent immediate breakage on nightly. Note that this is unstable in both
  location.
* `HashMap::with_hash_state` - renamed
* `HashMap::with_capacity_and_hash_state` - renamed
* `HashSet::with_hash_state` - renamed
* `HashSet::with_capacity_and_hash_state` - renamed

Closes #27713

The deny(warnings) attribute is now enabled for tests so we need to weed out
these warnings as well.

This splits the output of panics into two lines as proposed in #15239 and adds a
note about how to get a backtrace. Because the default panic message consists of
multiple lines now, this changes the test runner's failure output to not indent
the first line anymore.

Fixes #15239 and fixes #11704.

This commit implements the stabilization of the custom hasher support intended
for 1.7 but left out due to some last-minute questions that needed some
decisions. A summary of the actions done in this PR are:

Stable

* `std::hash::BuildHasher`
* `BuildHasher::Hasher`
* `BuildHasher::build_hasher`
* `std::hash::BuildHasherDefault`
* `HashMap::with_hasher`
* `HashMap::with_capacity_and_hasher`
* `HashSet::with_hasher`
* `HashSet::with_capacity_and_hasher`
* `std::collections::hash_map::RandomState`
* `RandomState::new`

Deprecated

* `std::collections::hash_state`
* `std::collections::hash_state::HashState` - this trait was also moved into
  `std::hash` with a reexport here to ensure that we can have a blanket impl to
  prevent immediate breakage on nightly. Note that this is unstable in both
  location.
* `HashMap::with_hash_state` - renamed
* `HashMap::with_capacity_and_hash_state` - renamed
* `HashSet::with_hash_state` - renamed
* `HashSet::with_capacity_and_hash_state` - renamed

Closes #27713

- Successful merges: #31172, #31177, #31211
- Failed merges:

r? @EddyB or @nrc

On all platforms, reading from stdin where the actual stdin isn't present should
return 0 bytes as having been read rather than the entire buffer.

On Windows, handle the case where we're inheriting stdio handles but one of them
isn't present. Currently the behavior is to fail returning an I/O error but
instead this commit corrects it to detecting this situation and propagating the
non-set handle.

Closes #31167

The previous example did not do what its description said. In it panicked on integer overflow in debug mode, and went into an infinite loop in release mode (wrapping back to 0 after printing 254).

The previous example did not do what its description said. In it panicked on integer overflow in debug mode, and went into an infinite loop in release mode (wrapping back to 0 after printing 254).

This fixes #23880, a scoping bug in which items in a block are shadowed by local variables and type parameters that are in scope.

After this PR, an item in a block will shadow any local variables or type parameters above the item in the scope hierarchy. Items in a block will continue to be shadowed by local variables in the same block (even if the item is defined after the local variable).

This is a [breaking-change]. For example, the following code breaks:
```rust
fn foo() {
    let mut f = 1;
    {
        fn f() {}
        f += 1; // This will resolve to the function instead of the local variable
    }
}

The note will only be shown on the first panic.

Fixes #31073
r? @EddyB

- Successful merges: #31152, #31184, #31189, #31192, #31197, #31199, #31201
- Failed merges:

Fixes #30633

Fixes #31181

Closes #31195

r? @steveklabnik

r? @steveklabnik

it is pre-RFC1214 junk and completely useless.

r? @nikomatsakis

cc #31135 rust-lang/rfcs#1462 #30923 @retep998
r? @pnkfelix

This fixes a bug in which items in a block are shadowed by local variables and type parameters that are in scope.
It is a [breaking-change]. For example, the following code breaks:

```rust
fn foo() {
    let mut f = 1;
    {
        fn f() {}
        f += 1; // This will now resolve to the function instead of the local variable
    }
}
```

Any breakage can be fixed by renaming the item that is no longer shadowed.

Fixes #30633

Fixes #31181

Closes #31195

On all platforms, reading from stdin where the actual stdin isn't present should
return 0 bytes as having been read rather than the entire buffer.

On Windows, handle the case where we're inheriting stdio handles but one of them
isn't present. Currently the behavior is to fail returning an I/O error but
instead this commit corrects it to detecting this situation and propagating the
non-set handle.

Closes #31167

This PR adds some minor error correction to the parser - if there is a missing ident, we recover and carry on. It also makes compilation more robust so that non-fatal errors (which is still most of them, unfortunately) in parsing do not cause us to abort compilation. The effect is that a program with a missing or incorrect ident can get all the way to type checking.

Also altered the format_args! syntax extension, and \#[derive(debug)], to maintain compatability.
r? @ nrc

It was removed in #30595.
Also delete the old learn-rust.md.

It was moved in #29538.

Also got rid of some code repetition in `const_eval`

error, by moving unexpected let check into the proper if-else clause