Rollup merge of rust-lang#106923 - mejrs:fluent_err, r=davidtwco

Restore behavior when primary bundle is missing

Fixes rust-lang#106755 by restoring some of the behavior prior to rust-lang#106427

Still, I have no idea how this debug assertion can even hit while using `en-US` as primary  bundle.

r? ``@davidtwco``

compiler/rustc_error_messages/src/lib.rs

@@ -135,7 +135,10 @@ pub fn fluent_bundle(
 
     let fallback_locale = langid!("en-US");
     let requested_fallback_locale = requested_locale.as_ref() == Some(&fallback_locale);
-
+    trace!(?requested_fallback_locale);
+    if requested_fallback_locale && additional_ftl_path.is_none() {
+        return Ok(None);
+    }
     // If there is only `-Z additional-ftl-path`, assume locale is "en-US", otherwise use user
     // provided locale.
     let locale = requested_locale.clone().unwrap_or(fallback_locale);
@@ -153,7 +156,7 @@ pub fn fluent_bundle(
     bundle.set_use_isolating(with_directionality_markers);
 
     // If the user requests the default locale then don't try to load anything.
-    if !requested_fallback_locale && let Some(requested_locale) = requested_locale {
+    if let Some(requested_locale) = requested_locale {
         let mut found_resources = false;
         for sysroot in user_provided_sysroot.iter_mut().chain(sysroot_candidates.iter_mut()) {
             sysroot.push("share");

compiler/rustc_errors/src/translation.rs

@@ -1,4 +1,4 @@
-use crate::error::TranslateError;
+use crate::error::{TranslateError, TranslateErrorKind};
 use crate::snippet::Style;
 use crate::{DiagnosticArg, DiagnosticMessage, FluentBundle};
 use rustc_data_structures::sync::Lrc;
@@ -95,6 +95,16 @@ pub trait Translate {
                 // The primary bundle was present and translation succeeded
                 Some(Ok(t)) => t,
 
+                // If `translate_with_bundle` returns `Err` with the primary bundle, this is likely
+                // just that the primary bundle doesn't contain the message being translated, so
+                // proceed to the fallback bundle.
+                Some(Err(
+                    primary @ TranslateError::One {
+                        kind: TranslateErrorKind::MessageMissing, ..
+                    },
+                )) => translate_with_bundle(self.fallback_fluent_bundle())
+                    .map_err(|fallback| primary.and(fallback))?,
+
                 // Always yeet out for errors on debug (unless
                 // `RUSTC_TRANSLATION_NO_DEBUG_ASSERT` is set in the environment - this allows
                 // local runs of the test suites, of builds with debug assertions, to test the
@@ -106,9 +116,8 @@ pub trait Translate {
                     do yeet primary
                 }
 
-                // If `translate_with_bundle` returns `Err` with the primary bundle, this is likely
-                // just that the primary bundle doesn't contain the message being translated or
-                // something else went wrong) so proceed to the fallback bundle.
+                // ..otherwise, for end users, an error about this wouldn't be useful or actionable, so
+                // just hide it and try with the fallback bundle.
                 Some(Err(primary)) => translate_with_bundle(self.fallback_fluent_bundle())
                     .map_err(|fallback| primary.and(fallback))?,
 

tests/ui/issues/issue-106755.rs

@@ -0,0 +1,19 @@
+// compile-flags:-Ztranslate-lang=en_US
+
+#![feature(negative_impls)]
+#![feature(marker_trait_attr)]
+
+#[marker]
+trait MyTrait {}
+
+struct TestType<T>(::std::marker::PhantomData<T>);
+
+unsafe impl<T: MyTrait + 'static> Send for TestType<T> {}
+
+impl<T: MyTrait> !Send for TestType<T> {} //~ ERROR found both positive and negative implementation
+
+unsafe impl<T: 'static> Send for TestType<T> {} //~ ERROR conflicting implementations
+
+impl !Send for TestType<i32> {}
+
+fn main() {}

tests/ui/issues/issue-106755.stderr

@@ -0,0 +1,22 @@
+error[E0751]: found both positive and negative implementation of trait `Send` for type `TestType<_>`:
+  --> $DIR/issue-106755.rs:13:1
+   |
+LL | unsafe impl<T: MyTrait + 'static> Send for TestType<T> {}
+   | ------------------------------------------------------ positive implementation here
+LL |
+LL | impl<T: MyTrait> !Send for TestType<T> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ negative implementation here
+
+error[E0119]: conflicting implementations of trait `Send` for type `TestType<_>`
+  --> $DIR/issue-106755.rs:15:1
+   |
+LL | unsafe impl<T: MyTrait + 'static> Send for TestType<T> {}
+   | ------------------------------------------------------ first implementation here
+...
+LL | unsafe impl<T: 'static> Send for TestType<T> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `TestType<_>`
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0119, E0751.
+For more information about an error, try `rustc --explain E0119`.