Per https://www.freedesktop.org/software/systemd/man/os-release.html,

> Variable assignment values must be enclosed in double or single quotes
> if they include spaces, semicolons or other special characters outside
> of A–Z, a–z, 0–9. (Assignments that do not include these special
> characters may be enclosed in quotes too, but this is optional.)

So, past `ID=nixos`, let's also check for `ID='nixos'` and `ID="nixos"`.

One of these is necessary between NixOS/nixpkgs#162168 and
NixOS/nixpkgs#164068, but this seems more correct either way.

Eric figured out the fix to this almost 2 years ago, I just didn't read his comment carefully enough at the timme.
The issue was that fake rustc and fake rustdoc were inconsistent about when they passed `--sysroot` to the real compiler.
Change them to consistently only pass it when `--target` is present.

… for a private module

Introduce a `DiagnosticMessage` type that will enable diagnostic
messages to be simple strings or Fluent identifiers.
`DiagnosticMessage` is now used in the implementation of the standard
`DiagnosticBuilder` APIs.

Signed-off-by: David Wood <[email protected]>

`MultiSpan` contains labels, which are more complicated with the
introduction of diagnostic translation and will use types from
`rustc_errors` - however, `rustc_errors` depends on `rustc_span` so
`rustc_span` cannot use types like `DiagnosticMessage` without
dependency cycles. Introduce a new `rustc_error_messages` crate that can
contain `DiagnosticMessage` and `MultiSpan`.

Signed-off-by: David Wood <[email protected]>

This commit updates the signatures of all diagnostic functions to accept
types that can be converted into a `DiagnosticMessage`. This enables
existing diagnostic calls to continue to work as before and Fluent
identifiers to be provided. The `SessionDiagnostic` derive just
generates normal diagnostic calls, so these APIs had to be modified to
accept Fluent identifiers.

In addition, loading of the "fallback" Fluent bundle, which contains the
built-in English messages, has been implemented.

Each diagnostic now has "arguments" which correspond to variables in the
Fluent messages (necessary to render a Fluent message) but no API for
adding arguments has been added yet. Therefore, diagnostics (that do not
require interpolation) can be converted to use Fluent identifiers and
will be output as before.

Extend loading of Fluent bundles so that bundles can be loaded from the
sysroot based on the language requested by the user, or using a nightly
flag.

Sysroot bundles are loaded from `$sysroot/share/locale/$locale/*.ftl`.

Signed-off-by: David Wood <[email protected]>

Various small changes to comments, like wrapping code in backticks,
changing comments to doc comments and adding newlines.

Signed-off-by: David Wood <[email protected]>

Move the handling of `Span` or `(Span, Applicability)` types in
`#[suggestion]` attributes to its own function.

Signed-off-by: David Wood <[email protected]>

Non-subdiagnostic fields (i.e. those that don't have `#[label]`
attributes or similar and are just additional context) have to be added
as arguments for Fluent messages to refer them. This commit extends the
`SessionDiagnostic` derive to do this for all fields that do not have
attributes and introduces an `IntoDiagnosticArg` trait that is
implemented on all types that can be converted to a argument for Fluent.

Signed-off-by: David Wood <[email protected]>

Fluent diagnostics can insert directionality isolation markers around
interpolated variables indicating that there may be a shift from
right-to-left to left-to-right text (or vice-versa). These are disabled
because they are sometimes visible in the error output, but may be worth
investigating in future (for example: if type names are left-to-right
and the surrounding diagnostic messages are right-to-left, then these
might be helpful).

Signed-off-by: David Wood <[email protected]>

Small commit adding backticks around types and annotations in the error
messages from the session diagnostic derive.

Signed-off-by: David Wood <[email protected]>

Signed-off-by: David Wood <[email protected]>

Small commit renaming `#[message]` to `#[primary_span]` as this more
accurately reflects what it does now.

Signed-off-by: David Wood <[email protected]>

A call to `set_arg` is generated for every field of a
`SessionDiagnostic` struct without attributes, but not all types support
being an argument, so `#[no_arg]` is introduced to skip these fields.

Signed-off-by: David Wood <[email protected]>

In an effort to make it easier to port diagnostics to
`SessionDiagnostic` (for translation) and since translation slugs could
replace error codes, make error codes optional in the
`SessionDiagnostic` derive.

Signed-off-by: David Wood <[email protected]>

Extends support for generating `DiagnosticMessage::FluentIdentifier`
messages from `SessionDiagnostic` derive to `#[label]`.

Signed-off-by: David Wood <[email protected]>

Signed-off-by: David Wood <[email protected]>

Extends support for generating `DiagnosticMessage::FluentIdentifier`
messages from `SessionDiagnostic` derive to `#[suggestion]`.

Signed-off-by: David Wood <[email protected]>

If the user requests a diagnostic locale of "en-US" then it doesn't make
sense to try and load that from the `$sysroot` because it is just the
default built-in locale.

Signed-off-by: David Wood <[email protected]>

Removes `expected_pluralize` parameter from diagnostic struct which is
no longer necessary as the Fluent message can determine the correct
pluralization.

Signed-off-by: David Wood <[email protected]>

Add some links to the Fluent documentation to
`DiagnosticMessage::FluentIdentifier` which explain what a Fluent
message and attribute are.

Signed-off-by: David Wood <[email protected]>

Add an option for enabling and disabling Fluent's directionality
isolation markers in output. Disabled by default as these can render in
some terminals and applications.

Signed-off-by: David Wood <[email protected]>

`FluentId` is the type alias that is used everywhere else so it should
be used here too so that this doesn't need updated if the alias changes.

Signed-off-by: David Wood <[email protected]>

Unfortunately, fluent comes with a lot of dependencies and these need to
be added to the whitelist.

Signed-off-by: David Wood <[email protected]>

Conditional on the parallel compiler being enabled, use a different
`IntlLangMemoizer` which supports being sent between threads in
`FluentBundle`.

Signed-off-by: David Wood <[email protected]>

bootstrap.py: nixos check in /etc/os-release with quotes

Per https://www.freedesktop.org/software/systemd/man/os-release.html,

> Variable assignment values must be enclosed in double or single quotes
> if they include spaces, semicolons or other special characters outside
> of A–Z, a–z, 0–9. (Assignments that do not include these special
> characters may be enclosed in quotes too, but this is optional.)

So, past `ID=nixos`, let's also check for `ID='nixos'` and `ID="nixos"`.

One of these is necessary between NixOS/nixpkgs#162168 and
NixOS/nixpkgs#164068, but this seems more correct either way.

Fix `x doc --stage 0 compiler`

Eric figured out the fix to this almost 2 years ago, I just didn't read his comment carefully enough at the timme.
The issue was that fake rustc and fake rustdoc were inconsistent about when they passed `--sysroot` to the real compiler.
Change them to consistently only pass it when `--target` is present.

cc rust-lang#74976 (comment)
Fixes rust-lang#79980

r? ``@ehuss``

…=oli-obk

diagnostics: translation infrastructure

An implementation of the infrastructure required to have translatable diagnostic messages.

- Introduces a `DiagnosticMessage` type which can represent both the current non-translatable messages and identifiers for [Fluent](https://projectfluent.org/).
- Modifies current diagnostic API so that existing calls still work but `DiagnosticMessage`s can be provided too.
- Adds support for always loading a "fallback bundle" containing the English diagnostic messages, which are used when a `DiagnosticMessage::FluentIdentifier` is used in a diagnostic being emitted.
- Adds support for loading a "primary bundle" which contains the user's preferred language translation, and is used preferentially when it contains a diagnostic message being emitted. Primary bundles are loaded either from the path provided to `-Ztranslate-alternate-ftl` (for testing), or from the sysroot at `$sysroot/locale/$locale/*.ftl` given a locale with `-Ztranslate-lang` (which is parsed as a language identifier).
- Adds "diagnostic args" which enable normally-interpolated variables to be made available as variables for Fluent messages to use.
- Updates `#[derive(SessionDiagnostic)]` so that it can only be used for translatable diagnostics and update the handful of diagnostics which used the derive to be translatable.

For example, the following diagnostic...

```rust
#[derive(SessionDiagnostic)]
#[error = "E0195"]
pub struct LifetimesOrBoundsMismatchOnTrait {
    #[message = "lifetime parameters or bounds on {item_kind} `{ident}` do not match the trait declaration"]
    #[label = "lifetimes do not match {item_kind} in trait"]
    pub span: Span,
    #[label = "lifetimes in impl do not match this {item_kind} in trait"]
    pub generics_span: Option<Span>,
    pub item_kind: &'static str,
    pub ident: Ident,
}
```

...becomes...

```rust
#[derive(SessionDiagnostic)]
#[error(code = "E0195", slug = "typeck-lifetimes-or-bounds-mismatch-on-trait")]
pub struct LifetimesOrBoundsMismatchOnTrait {
    #[primary_span]
    #[label]
    pub span: Span,
    #[label = "generics-label"]
    pub generics_span: Option<Span>,
    pub item_kind: &'static str,
    pub ident: Ident,
}
```

```fluent
typeck-lifetimes-or-bounds-mismatch-on-trait =
    lifetime parameters or bounds on {$item_kind} `{$ident}` do not match the trait declaration
    .label = lifetimes do not match {$item_kind} in trait
    .generics-label = lifetimes in impl do not match this {$item_kind} in trait
```

r? `@estebank`
cc `@oli-obk` `@Manishearth`

…n1011

Note invariance reason for FnDef types

Fixes rust-lang#95272. Is it worthwhile even printing a variance explanation here? Or should I try to track down which function parameter is responsible for the invariance?

r? ``@Aaron1011`` since you wrote rust-lang#89336

…raits-in-scope-primitive, r=jyn514

Fix intra doc link ICE when trying to get traits in scope for primitive

Fixes rust-lang#95633.

I think ``@notriddle`` was the one who worked on this part of the code last so:

r? ``@notriddle``