Lint against escape sequences in Fluent files

compiler/rustc_codegen_llvm/messages.ftl

@@ -27,7 +27,8 @@ codegen_llvm_error_calling_dlltool =
     Error calling dlltool: {$error}
 
 codegen_llvm_dlltool_fail_import_library =
-    Dlltool could not create import library: {$stdout}\n{$stderr}
+    Dlltool could not create import library: {$stdout}
+    {$stderr}
 
 codegen_llvm_target_feature_disable_or_enable =
     the target features {$features} must all be either enabled or disabled together

compiler/rustc_const_eval/messages.ftl

@@ -39,17 +39,25 @@ const_eval_unstable_const_fn = `{$def_path}` is not yet stable as a const fn
 const_eval_unallowed_mutable_refs =
     mutable references are not allowed in the final value of {$kind}s
     .teach_note =
-        References in statics and constants may only refer to immutable values.\n\n
+        References in statics and constants may only refer to immutable values.
+
+
         Statics are shared everywhere, and if they refer to mutable data one might violate memory
-        safety since holding multiple mutable references to shared data is not allowed.\n\n
+        safety since holding multiple mutable references to shared data is not allowed.
+
+
         If you really want global mutable state, try using static mut or a global UnsafeCell.
 
 const_eval_unallowed_mutable_refs_raw =
     raw mutable references are not allowed in the final value of {$kind}s
     .teach_note =
-        References in statics and constants may only refer to immutable values.\n\n
+        References in statics and constants may only refer to immutable values.
+
+
         Statics are shared everywhere, and if they refer to mutable data one might violate memory
-        safety since holding multiple mutable references to shared data is not allowed.\n\n
+        safety since holding multiple mutable references to shared data is not allowed.
+
+
         If you really want global mutable state, try using static mut or a global UnsafeCell.
 
 const_eval_non_const_fmt_macro_call =

compiler/rustc_incremental/messages.ftl

@@ -24,7 +24,7 @@ incremental_field_associated_value_expected = associated value expected for `{$n
 incremental_no_field = no field `{$name}`
 
 incremental_assertion_auto =
-    `except` specified DepNodes that can not be affected for \"{$name}\": \"{$e}\"
+    `except` specified DepNodes that can not be affected for "{$name}": "{$e}"
 
 incremental_undefined_clean_dirty_assertions_item =
     clean/dirty auto-assertions not yet defined for Node::Item.node={$kind}

compiler/rustc_lint/messages.ftl

@@ -91,7 +91,7 @@ lint_ty_qualified = usage of qualified `ty::{$ty}`
 lint_lintpass_by_hand = implementing `LintPass` by hand
     .help = try using `declare_lint_pass!` or `impl_lint_pass!` instead
 
-lint_non_existant_doc_keyword = found non-existing keyword `{$keyword}` used in `#[doc(keyword = \"...\")]`
+lint_non_existant_doc_keyword = found non-existing keyword `{$keyword}` used in `#[doc(keyword = "...")]`
     .help = only existing keywords are allowed in core/std
 
 lint_diag_out_of_impl =

compiler/rustc_macros/src/diagnostics/fluent.rs

@@ -111,6 +111,18 @@ pub(crate) fn fluent_messages(input: proc_macro::TokenStream) -> proc_macro::Tok
             .emit();
         return failed(&crate_name);
     }
+    let mut bad = false;
+    for esc in ["\\n", "\\\"", "\\'"] {
+        for _ in resource_contents.matches(esc) {
+            bad = true;
+            Diagnostic::spanned(resource_span, Level::Error, format!("invalid escape `{esc}` in Fluent resource"))
+                .note("Fluent does not interpret these escape sequences (<https://projectfluent.org/fluent/guide/special.html>)")
+                .emit();
+        }
+    }
+    if bad {
+        return failed(&crate_name);
+    }
 
     let resource = match FluentResource::try_new(resource_contents) {
         Ok(resource) => resource,

tests/ui-fulldeps/fluent-messages/invalid-escape.ftl

@@ -0,0 +1 @@
+no_crate_bad_escape = don't use \n, \', or \"

tests/ui-fulldeps/fluent-messages/test.rs

@@ -92,3 +92,12 @@ mod missing_message_ref {
     fluent_messages! { "./missing-message-ref.ftl" }
     //~^ ERROR referenced message `message` does not exist
 }
+
+mod bad_escape {
+    use super::fluent_messages;
+
+    fluent_messages! { "./invalid-escape.ftl" }
+    //~^ ERROR invalid escape `\n`
+    //~| ERROR invalid escape `\"`
+    //~| ERROR invalid escape `\'`
+}

tests/ui-fulldeps/fluent-messages/test.stderr

@@ -83,5 +83,29 @@ LL |     fluent_messages! { "./missing-message-ref.ftl" }
    |
    = help: you may have meant to use a variable reference (`{$message}`)
 
-error: aborting due to 10 previous errors
+error: invalid escape `\n` in Fluent resource
+  --> $DIR/test.rs:99:24
+   |
+LL |     fluent_messages! { "./invalid-escape.ftl" }
+   |                        ^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: os-specific message
+
+error: invalid escape `\"` in Fluent resource
+  --> $DIR/test.rs:99:24
+   |
+LL |     fluent_messages! { "./invalid-escape.ftl" }
+   |                        ^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: os-specific message
+
+error: invalid escape `\'` in Fluent resource
+  --> $DIR/test.rs:99:24
+   |
+LL |     fluent_messages! { "./invalid-escape.ftl" }
+   |                        ^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: os-specific message
+
+error: aborting due to 13 previous errors
 

tests/ui-fulldeps/internal-lints/existing_doc_keyword.stderr

@@ -1,4 +1,4 @@
-error: found non-existing keyword `tadam` used in `#[doc(keyword = \"...\")]`
+error: found non-existing keyword `tadam` used in `#[doc(keyword = "...")]`
   --> $DIR/existing_doc_keyword.rs:10:1
    |
 LL | #[doc(keyword = "tadam")]