Generate lint diagnostic message from BuiltinLintDiag

Translation of the lint message happens when the actual diagnostic is
created, not when the lint is buffered. Generating the message from
BuiltinLintDiag ensures that all required data to construct the message
is preserved in the LintBuffer, eventually allowing the messages to be
moved to fluent.

Remove the `msg` field from BufferedEarlyLint, it is either generated
from the data in the BuiltinLintDiag or stored inside
BuiltinLintDiag::Normal.

compiler/rustc_lint_defs/src/lib.rs

@@ -6,6 +6,7 @@ use rustc_data_structures::stable_hasher::{
     HashStable, StableCompare, StableHasher, ToStableHashKey,
 };
 use rustc_error_messages::{DiagMessage, MultiSpan};
+use rustc_hir::def::Namespace;
 use rustc_hir::HashStableContext;
 use rustc_hir::HirId;
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
@@ -569,15 +570,28 @@ pub struct AmbiguityErrorDiag {
 // becomes hacky (and it gets allocated).
 #[derive(Debug)]
 pub enum BuiltinLintDiag {
-    Normal,
+    Normal(DiagMessage),
     AbsPathWithModule(Span),
-    ProcMacroDeriveResolutionFallback(Span),
+    ProcMacroDeriveResolutionFallback {
+        span: Span,
+        ns: Namespace,
+        ident: Ident,
+    },
     MacroExpandedMacroExportsAccessedByAbsolutePaths(Span),
     ElidedLifetimesInPaths(usize, Span, bool, Span),
     UnknownCrateTypes(Span, String, String),
-    UnusedImports(String, Vec<(Span, String)>, Option<Span>),
+    UnusedImports {
+        fix_msg: String,
+        fixes: Vec<(Span, String)>,
+        test_module_span: Option<Span>,
+        span_snippets: Vec<String>,
+    },
     RedundantImport(Vec<(Span, bool)>, Ident),
-    DeprecatedMacro(Option<Symbol>, Span),
+    DeprecatedMacro {
+        suggestion: Option<Symbol>,
+        span: Span,
+        message: String,
+    },
     MissingAbi(Span, Abi),
     UnusedDocComment(Span),
     UnusedBuiltinAttribute {
@@ -585,11 +599,15 @@ pub enum BuiltinLintDiag {
         macro_name: String,
         invoc_span: Span,
     },
-    PatternsInFnsWithoutBody(Span, Ident),
+    PatternsInFnsWithoutBody {
+        span: Span,
+        ident: Ident,
+        is_foreign: bool,
+    },
     LegacyDeriveHelpers(Span),
     ProcMacroBackCompat(String),
     OrPatternsBackCompat(Span, String),
-    ReservedPrefix(Span),
+    ReservedPrefix(Span, String),
     TrailingMacro(bool, Ident),
     BreakWithLabelAndLoop(Span),
     UnicodeTextFlow(Span, String),
@@ -605,6 +623,7 @@ pub enum BuiltinLintDiag {
         /// Span of the single use, or None if the lifetime is never used.
         /// If true, the lifetime will be fully elided.
         use_span: Option<(Span, bool)>,
+        ident: Ident,
     },
     NamedArgumentUsedPositionally {
         /// Span where the named argument is used by position and will be replaced with the named
@@ -619,7 +638,10 @@ pub enum BuiltinLintDiag {
         /// Indicates if the named argument is used as a width/precision for formatting
         is_formatting_arg: bool,
     },
-    ByteSliceInPackedStructWithDerive,
+    ByteSliceInPackedStructWithDerive {
+        // FIXME: enum of byte/string
+        ty: String,
+    },
     UnusedExternCrate {
         removal_span: Span,
     },
@@ -661,6 +683,7 @@ pub enum BuiltinLintDiag {
     RedundantImportVisibility {
         span: Span,
         max_vis: String,
+        import_vis: String,
     },
     MaybeTypo {
         span: Span,
@@ -675,9 +698,6 @@ pub struct BufferedEarlyLint {
     /// The span of code that we are linting on.
     pub span: MultiSpan,
 
-    /// The lint message.
-    pub msg: DiagMessage,
-
     /// The `NodeId` of the AST node that generated the lint.
     pub node_id: NodeId,
 
@@ -705,12 +725,10 @@ impl LintBuffer {
         lint: &'static Lint,
         node_id: NodeId,
         span: MultiSpan,
-        msg: impl Into<DiagMessage>,
         diagnostic: BuiltinLintDiag,
     ) {
         let lint_id = LintId::of(lint);
-        let msg = msg.into();
-        self.add_early_lint(BufferedEarlyLint { lint_id, node_id, span, msg, diagnostic });
+        self.add_early_lint(BufferedEarlyLint { lint_id, node_id, span, diagnostic });
     }
 
     pub fn take(&mut self, id: NodeId) -> Vec<BufferedEarlyLint> {
@@ -725,7 +743,7 @@ impl LintBuffer {
         sp: impl Into<MultiSpan>,
         msg: impl Into<DiagMessage>,
     ) {
-        self.add_lint(lint, id, sp.into(), msg, BuiltinLintDiag::Normal)
+        self.add_lint(lint, id, sp.into(), BuiltinLintDiag::Normal(msg.into()))
     }
 
     pub fn buffer_lint_with_diagnostic(
@@ -733,10 +751,9 @@ impl LintBuffer {
         lint: &'static Lint,
         id: NodeId,
         sp: impl Into<MultiSpan>,
-        msg: impl Into<DiagMessage>,
         diagnostic: BuiltinLintDiag,
     ) {
-        self.add_lint(lint, id, sp.into(), msg, diagnostic)
+        self.add_lint(lint, id, sp.into(), diagnostic)
     }
 }