From 552eb3295a06a1a6841686f064647c4d847552cb Mon Sep 17 00:00:00 2001
From: David Wood <david.wood@huawei.com>
Date: Mon, 23 May 2022 18:24:55 +0100
Subject: macros: introduce `fluent_messages` macro

Adds a new `fluent_messages` macro which performs compile-time
validation of the compiler's Fluent resources (i.e. that the resources
parse and don't multiply define the same messages) and generates
constants that make using those messages in diagnostics more ergonomic.

For example, given the following invocation of the macro..

```ignore (rust)
fluent_messages! {
    typeck => "./typeck.ftl",
}
```
..where `typeck.ftl` has the following contents..

```fluent
typeck-field-multiply-specified-in-initializer =
    field `{$ident}` specified more than once
    .label = used more than once
    .label-previous-use = first use of `{$ident}`
```
...then the macro parse the Fluent resource, emitting a diagnostic if it
fails to do so, and will generate the following code:

```ignore (rust)
pub static DEFAULT_LOCALE_RESOURCES: &'static [&'static str] = &[
    include_str!("./typeck.ftl"),
];

mod fluent_generated {
    mod typeck {
        pub const field_multiply_specified_in_initializer: DiagnosticMessage =
            DiagnosticMessage::fluent("typeck-field-multiply-specified-in-initializer");
        pub const field_multiply_specified_in_initializer_label_previous_use: DiagnosticMessage =
            DiagnosticMessage::fluent_attr(
                "typeck-field-multiply-specified-in-initializer",
                "previous-use-label"
            );
    }
}
```

When emitting a diagnostic, the generated constants can be used as
follows:

```ignore (rust)
let mut err = sess.struct_span_err(
    span,
    fluent::typeck::field_multiply_specified_in_initializer
);
err.span_default_label(span);
err.span_label(
    previous_use_span,
    fluent::typeck::field_multiply_specified_in_initializer_label_previous_use
);
err.emit();
```

Signed-off-by: David Wood <david.wood@huawei.com>
---
 compiler/rustc_errors/src/lib.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'compiler/rustc_errors/src')

diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index d2f50d5df54..5b9b65da343 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -31,8 +31,8 @@ use rustc_data_structures::stable_hasher::StableHasher;
 use rustc_data_structures::sync::{self, Lock, Lrc};
 use rustc_data_structures::AtomicRef;
 pub use rustc_error_messages::{
-    fallback_fluent_bundle, fluent_bundle, DiagnosticMessage, FluentBundle, LanguageIdentifier,
-    LazyFallbackBundle, MultiSpan, SpanLabel, DEFAULT_LOCALE_RESOURCES,
+    fallback_fluent_bundle, fluent, fluent_bundle, DiagnosticMessage, FluentBundle,
+    LanguageIdentifier, LazyFallbackBundle, MultiSpan, SpanLabel, DEFAULT_LOCALE_RESOURCES,
 };
 pub use rustc_lint_defs::{pluralize, Applicability};
 use rustc_span::source_map::SourceMap;
-- 
cgit 1.4.1-3-g733a5