Rollup merge of rust-lang#95512 - davidtwco:diagnostic-translation, r=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`

Author: Dylan-DPC

Diff for: Cargo.lock

@@ -1238,6 +1238,40 @@ dependencies = [
  "miniz_oxide",
 ]
 
+[[package]]
+name = "fluent-bundle"
+version = "0.15.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e242c601dec9711505f6d5bbff5bedd4b61b2469f2e8bb8e57ee7c9747a87ffd"
+dependencies = [
+ "fluent-langneg",
+ "fluent-syntax",
+ "intl-memoizer",
+ "intl_pluralrules",
+ "rustc-hash",
+ "self_cell",
+ "smallvec",
+ "unic-langid",
+]
+
+[[package]]
+name = "fluent-langneg"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2c4ad0989667548f06ccd0e306ed56b61bd4d35458d54df5ec7587c0e8ed5e94"
+dependencies = [
+ "unic-langid",
+]
+
+[[package]]
+name = "fluent-syntax"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c0abed97648395c902868fee9026de96483933faa54ea3b40d652f7dfe61ca78"
+dependencies = [
+ "thiserror",
+]
+
 [[package]]
 name = "fnv"
 version = "1.0.7"
@@ -1782,6 +1816,26 @@ dependencies = [
  "cfg-if 1.0.0",
 ]
 
+[[package]]
+name = "intl-memoizer"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c310433e4a310918d6ed9243542a6b83ec1183df95dff8f23f87bb88a264a66f"
+dependencies = [
+ "type-map",
+ "unic-langid",
+]
+
+[[package]]
+name = "intl_pluralrules"
+version = "7.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b18f988384267d7066cc2be425e6faf352900652c046b6971d2e228d3b1c5ecf"
+dependencies = [
+ "tinystr",
+ "unic-langid",
+]
+
 [[package]]
 name = "itertools"
 version = "0.10.1"
@@ -2812,6 +2866,12 @@ dependencies = [
  "version_check",
 ]
 
+[[package]]
+name = "proc-macro-hack"
+version = "0.5.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dbf0c48bc1d91375ae5c3cd81e3722dff1abcf81a30960240640d223f59fe0e5"
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.30"
@@ -3645,13 +3705,29 @@ dependencies = [
 name = "rustc_error_codes"
 version = "0.0.0"
 
+[[package]]
+name = "rustc_error_messages"
+version = "0.0.0"
+dependencies = [
+ "fluent-bundle",
+ "fluent-syntax",
+ "intl-memoizer",
+ "rustc_data_structures",
+ "rustc_macros",
+ "rustc_serialize",
+ "rustc_span",
+ "tracing",
+ "unic-langid",
+]
+
 [[package]]
 name = "rustc_errors"
 version = "0.0.0"
 dependencies = [
  "annotate-snippets",
  "atty",
  "rustc_data_structures",
+ "rustc_error_messages",
  "rustc_lint_defs",
  "rustc_macros",
  "rustc_serialize",
@@ -3708,6 +3784,7 @@ dependencies = [
  "odht",
  "rustc_ast",
  "rustc_data_structures",
+ "rustc_error_messages",
  "rustc_feature",
  "rustc_index",
  "rustc_macros",
@@ -3864,6 +3941,7 @@ version = "0.0.0"
 dependencies = [
  "rustc_ast",
  "rustc_data_structures",
+ "rustc_error_messages",
  "rustc_hir",
  "rustc_macros",
  "rustc_serialize",
@@ -4573,6 +4651,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "self_cell"
+version = "0.10.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1ef965a420fe14fdac7dd018862966a4c14094f900e1650bbc71ddd7d580c8af"
+
 [[package]]
 name = "semver"
 version = "1.0.3"
@@ -5104,6 +5188,12 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "tinystr"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "29738eedb4388d9ea620eeab9384884fc3f06f586a2eddb56bedc5885126c7c1"
+
 [[package]]
 name = "tinyvec"
 version = "0.3.4"
@@ -5262,6 +5352,15 @@ dependencies = [
  "tracing-subscriber",
 ]
 
+[[package]]
+name = "type-map"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b6d3364c5e96cb2ad1603037ab253ddd34d7fb72a58bdddf4b7350760fc69a46"
+dependencies = [
+ "rustc-hash",
+]
+
 [[package]]
 name = "typenum"
 version = "1.12.0"
@@ -5316,6 +5415,49 @@ dependencies = [
  "unic-ucd-version",
 ]
 
+[[package]]
+name = "unic-langid"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "73328fcd730a030bdb19ddf23e192187a6b01cd98be6d3140622a89129459ce5"
+dependencies = [
+ "unic-langid-impl",
+ "unic-langid-macros",
+]
+
+[[package]]
+name = "unic-langid-impl"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1a4a8eeaf0494862c1404c95ec2f4c33a2acff5076f64314b465e3ddae1b934d"
+dependencies = [
+ "tinystr",
+]
+
+[[package]]
+name = "unic-langid-macros"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "18f980d6d87e8805f2836d64b4138cc95aa7986fa63b1f51f67d5fbff64dd6e5"
+dependencies = [
+ "proc-macro-hack",
+ "tinystr",
+ "unic-langid-impl",
+ "unic-langid-macros-impl",
+]
+
+[[package]]
+name = "unic-langid-macros-impl"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "29396ffd97e27574c3e01368b1a64267d3064969e4848e2e130ff668be9daa9f"
+dependencies = [
+ "proc-macro-hack",
+ "quote",
+ "syn",
+ "unic-langid-impl",
+]
+
 [[package]]
 name = "unic-ucd-version"
 version = "0.9.0"

Diff for: compiler/rustc_borrowck/src/borrowck_errors.rs

@@ -1,6 +1,6 @@
-use rustc_errors::{struct_span_err, DiagnosticBuilder, DiagnosticId, ErrorGuaranteed};
+use rustc_errors::{struct_span_err, DiagnosticBuilder, DiagnosticId, ErrorGuaranteed, MultiSpan};
 use rustc_middle::ty::{self, Ty, TyCtxt};
-use rustc_span::{MultiSpan, Span};
+use rustc_span::Span;
 
 impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
     crate fn cannot_move_when_borrowed(

Diff for: compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -1,7 +1,7 @@
 use either::Either;
 use rustc_const_eval::util::CallKind;
 use rustc_data_structures::fx::FxHashSet;
-use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
+use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::{AsyncGeneratorKind, GeneratorKind};
@@ -15,7 +15,7 @@ use rustc_middle::mir::{
 use rustc_middle::ty::{self, subst::Subst, suggest_constraining_type_params, PredicateKind, Ty};
 use rustc_mir_dataflow::move_paths::{InitKind, MoveOutIndex, MovePathIndex};
 use rustc_span::symbol::sym;
-use rustc_span::{BytePos, MultiSpan, Span};
+use rustc_span::{BytePos, Span};
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::TraitEngineExt as _;
 

Diff for: compiler/rustc_borrowck/src/diagnostics/region_name.rs

@@ -109,7 +109,7 @@ impl RegionName {
                     *span,
                     format!("lifetime `{}` represents this closure's body", self),
                 );
-                diag.note(&note);
+                diag.note(note);
             }
             RegionNameSource::AnonRegionFromArgument(RegionNameHighlight::CannotMatchHirTy(
                 span,

Diff for: compiler/rustc_builtin_macros/src/format.rs

@@ -7,11 +7,11 @@ use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::visit::{self, Visitor};
 use rustc_ast::{token, BlockCheckMode, UnsafeSource};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_errors::{pluralize, Applicability, PResult};
+use rustc_errors::{pluralize, Applicability, MultiSpan, PResult};
 use rustc_expand::base::{self, *};
 use rustc_parse_format as parse;
 use rustc_span::symbol::{sym, Ident, Symbol};
-use rustc_span::{InnerSpan, MultiSpan, Span};
+use rustc_span::{InnerSpan, Span};
 use smallvec::SmallVec;
 
 use std::borrow::Cow;
@@ -446,7 +446,9 @@ impl<'a, 'b> Context<'a, 'b> {
                                 .iter()
                                 .filter(|fmt| fmt.precision_span.is_some())
                                 .count();
-                        e.span_label(span, &format!(
+                        e.span_label(
+                            span,
+                            &format!(
                             "this precision flag adds an extra required argument at position {}, \
                              which is why there {} expected",
                             pos,
@@ -455,7 +457,8 @@ impl<'a, 'b> Context<'a, 'b> {
                             } else {
                                 format!("are {} arguments", count)
                             },
-                        ));
+                        ),
+                        );
                         if let Some(arg) = self.args.get(pos) {
                             e.span_label(
                                 arg.span,

Diff for: compiler/rustc_codegen_ssa/src/back/write.rs

@@ -1707,23 +1707,33 @@ impl SharedEmitter {
 
 impl Emitter for SharedEmitter {
     fn emit_diagnostic(&mut self, diag: &rustc_errors::Diagnostic) {
+        let fluent_args = self.to_fluent_args(diag.args());
         drop(self.sender.send(SharedEmitterMessage::Diagnostic(Diagnostic {
-            msg: diag.message(),
+            msg: self.translate_messages(&diag.message, &fluent_args).to_string(),
             code: diag.code.clone(),
             lvl: diag.level(),
         })));
         for child in &diag.children {
             drop(self.sender.send(SharedEmitterMessage::Diagnostic(Diagnostic {
-                msg: child.message(),
+                msg: self.translate_messages(&child.message, &fluent_args).to_string(),
                 code: None,
                 lvl: child.level,
             })));
         }
         drop(self.sender.send(SharedEmitterMessage::AbortIfErrors));
     }
+
     fn source_map(&self) -> Option<&Lrc<SourceMap>> {
         None
     }
+
+    fn fluent_bundle(&self) -> Option<&Lrc<rustc_errors::FluentBundle>> {
+        None
+    }
+
+    fn fallback_fluent_bundle(&self) -> &Lrc<rustc_errors::FluentBundle> {
+        panic!("shared emitter attempted to translate a diagnostic");
+    }
 }
 
 impl SharedEmitterMain {
@@ -1754,9 +1764,9 @@ impl SharedEmitterMain {
                     let msg = msg.strip_prefix("error: ").unwrap_or(&msg);
 
                     let mut err = match level {
-                        Level::Error { lint: false } => sess.struct_err(&msg).forget_guarantee(),
-                        Level::Warning => sess.struct_warn(&msg),
-                        Level::Note => sess.struct_note_without_error(&msg),
+                        Level::Error { lint: false } => sess.struct_err(msg).forget_guarantee(),
+                        Level::Warning => sess.struct_warn(msg),
+                        Level::Note => sess.struct_note_without_error(msg),
                         _ => bug!("Invalid inline asm diagnostic level"),
                     };
 

Diff for: compiler/rustc_driver/src/lib.rs

@@ -1172,9 +1172,13 @@ static DEFAULT_HOOK: SyncLazy<Box<dyn Fn(&panic::PanicInfo<'_>) + Sync + Send +
 /// When `install_ice_hook` is called, this function will be called as the panic
 /// hook.
 pub fn report_ice(info: &panic::PanicInfo<'_>, bug_report_url: &str) {
+    let fallback_bundle =
+        rustc_errors::fallback_fluent_bundle(false).expect("failed to load fallback fluent bundle");
     let emitter = Box::new(rustc_errors::emitter::EmitterWriter::stderr(
         rustc_errors::ColorConfig::Auto,
         None,
+        None,
+        fallback_bundle,
         false,
         false,
         None,
@@ -1209,7 +1213,7 @@ pub fn report_ice(info: &panic::PanicInfo<'_>, bug_report_url: &str) {
     }
 
     for note in &xs {
-        handler.note_without_error(note);
+        handler.note_without_error(note.as_ref());
     }
 
     // If backtraces are enabled, also print the query stack

Diff for: compiler/rustc_error_messages/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "rustc_error_messages"
+version = "0.0.0"
+edition = "2021"
+
+[lib]
+doctest = false
+
+[dependencies]
+fluent-bundle = "0.15.2"
+fluent-syntax = "0.11"
+intl-memoizer = "0.5.1"
+rustc_data_structures = { path = "../rustc_data_structures" }
+rustc_serialize = { path = "../rustc_serialize" }
+rustc_span = { path = "../rustc_span" }
+rustc_macros = { path = "../rustc_macros" }
+tracing = "0.1"
+unic-langid = { version = "0.9.0", features = ["macros"] }