Migrate most of rustc_builtin_macros to diagnostic impls

compiler/rustc_builtin_macros/messages.ftl

@@ -3,3 +3,149 @@ builtin_macros_requires_cfg_pattern =
     .label = cfg-pattern required
 
 builtin_macros_expected_one_cfg_pattern = expected 1 cfg-pattern
+
+builtin_macros_alloc_error_must_be_fn = alloc_error_handler must be a function
+
+builtin_macros_assert_requires_boolean = macro requires a boolean expression as an argument
+    .label = boolean expression required
+
+builtin_macros_assert_requires_expression = macro requires an expression as an argument
+    .suggestion = try removing semicolon
+
+builtin_macros_assert_missing_comma = unexpected string literal
+    .suggestion = try adding a comma
+
+builtin_macros_cfg_accessible_unspecified_path = `cfg_accessible` path is not specified
+builtin_macros_cfg_accessible_multiple_paths = multiple `cfg_accessible` paths are specified
+builtin_macros_cfg_accessible_literal_path = `cfg_accessible` path cannot be a literal
+builtin_macros_cfg_accessible_has_args = `cfg_accessible` path cannot accept arguments
+
+builtin_macros_cfg_accessible_indeterminate = cannot determine whether the path is accessible or not
+
+builtin_macros_concat_bytestr = cannot concatenate a byte string literal
+
+builtin_macros_concat_missing_literal = expected a literal
+    .note = only literals (like `"foo"`, `-42` and `3.14`) can be passed to `concat!()`
+
+builtin_macros_concat_bytes_missing_literal = expected a byte literal
+    .note = only byte literals (like `b"foo"`, `b's'` and `[3, 4, 5]`) can be passed to `concat_bytes!()`
+
+builtin_macros_concat_bytes_invalid = cannot concatenate {$lit_kind} literals
+    .byte_char = try using a byte character
+    .byte_str = try using a byte string
+    .number_array = try wrapping the number in an array
+
+builtin_macros_concat_bytes_oob = numeric literal is out of bounds
+
+builtin_macros_concat_bytes_non_u8 = numeric literal is not a `u8`
+
+builtin_macros_concat_bytes_array = cannot concatenate doubly nested array
+    .note = byte strings are treated as arrays of bytes
+    .help = try flattening the array
+
+builtin_macros_concat_bytes_bad_repeat = repeat count is not a positive number
+
+builtin_macros_concat_idents_missing_args = `concat_idents!()` takes 1 or more arguments
+builtin_macros_concat_idents_missing_comma = `concat_idents!()` expecting comma
+builtin_macros_concat_idents_ident_args = `concat_idents!()` requires ident args
+
+builtin_macros_bad_derive_target = `derive` may only be applied to `struct`s, `enum`s and `union`s
+    .label = not applicable here
+    .label2 = not a `struct`, `enum` or `union`
+
+builtin_macros_unexpected_lit = expected path to a trait, found literal
+    .label = not a trait
+    .str_lit = try using `#[derive({$sym})]`
+    .other = for example, write `#[derive(Debug)]` for `Debug`
+
+builtin_macros_derive_path_args_list = traits in `#[derive(...)]` don't accept arguments
+    .suggestion = remove the arguments
+
+builtin_macros_derive_path_args_value = traits in `#[derive(...)]` don't accept values
+    .suggestion = remove the value
+
+builtin_macros_derive_macro_call = `derive` cannot be used on items with type macros
+
+builtin_macros_cannot_derive_union = this trait cannot be derived for unions
+
+builtin_macros_no_default_variant = no default declared
+    .help = make a unit variant default by placing `#[default]` above it
+    .suggestion = make `{$ident}` default
+
+builtin_macros_multiple_defaults = multiple declared defaults
+    .label = first default
+    .additional = additional default
+    .note = only one variant can be default
+    .suggestion = make `{$ident}` default
+
+builtin_macros_non_unit_default = the `#[default]` attribute may only be used on unit enum variants
+    .help = consider a manual implementation of `Default`
+
+builtin_macros_non_exhaustive_default = default variant must be exhaustive
+    .label = declared `#[non_exhaustive]` here
+    .help = consider a manual implementation of `Default`
+
+builtin_macros_multiple_default_attrs = multiple `#[default]` attributes
+    .note = only one `#[default]` attribute is needed
+    .label = `#[default]` used here
+    .label_again = `#[default]` used again here
+    .help = try removing {$only_one ->
+    [true] this
+    *[false] these
+    }
+
+builtin_macros_default_arg = `#[default]` attribute does not accept a value
+    .suggestion = try using `#[default]`
+
+builtin_macros_env_takes_args = `env!()` takes 1 or 2 arguments
+
+builtin_macros_env_not_defined = environment variable `{$var}` not defined at compile time
+    .cargo = Cargo sets build script variables at run time. Use `std::env::var("{$var}")` instead
+    .other = use `std::env::var("{$var}")` to read the variable at run time
+
+builtin_macros_format_requires_string = requires at least a format string argument
+
+builtin_macros_format_duplicate_arg = duplicate argument named `{$ident}`
+    .label1 = previously here
+    .label2 = duplicate argument
+
+builtin_macros_format_positional_after_named = positional arguments cannot follow named arguments
+    .label = positional arguments must be before named arguments
+    .named_args = named argument
+
+builtin_macros_format_string_invalid = invalid format string: {$desc}
+    .label = {$label1} in format string
+    .note = {$note}
+    .second_label = {$label}
+
+builtin_macros_sugg = consider using a positional formatting argument instead
+
+builtin_macros_format_no_arg_named = there is no argument named `{$name}`
+    .note = did you intend to capture a variable `{$name}` from the surrounding scope?
+    .note2 = to avoid ambiguity, `format_args!` cannot capture variables when the format string is expanded from a macro
+
+builtin_macros_format_unknown_trait = unknown format trait `{$ty}`
+    .note = the only appropriate formatting traits are:
+                                            - ``, which uses the `Display` trait
+                                            - `?`, which uses the `Debug` trait
+                                            - `e`, which uses the `LowerExp` trait
+                                            - `E`, which uses the `UpperExp` trait
+                                            - `o`, which uses the `Octal` trait
+                                            - `p`, which uses the `Pointer` trait
+                                            - `b`, which uses the `Binary` trait
+                                            - `x`, which uses the `LowerHex` trait
+                                            - `X`, which uses the `UpperHex` trait
+    .suggestion = use the `{$trait_name}` trait
+
+builtin_macros_format_unused_arg = {$named ->
+    [true] named argument
+    *[false] argument
+    } never used
+
+builtin_macros_format_unused_args = multiple unused formatting arguments
+    .label = multiple missing formatting specifiers
+
+builtin_macros_format_pos_mismatch = {$n} positional {$n ->
+    [one] argument
+    *[more] arguments
+    } in format string, but {$desc}

compiler/rustc_builtin_macros/src/alloc_error_handler.rs

@@ -1,3 +1,4 @@
+use crate::errors;
 use crate::util::check_builtin_macro_attribute;
 
 use rustc_ast::ptr::P;
@@ -31,7 +32,7 @@ pub fn expand(
         {
             (item, true, ecx.with_def_site_ctxt(fn_kind.sig.span))
         } else {
-            ecx.sess.parse_sess.span_diagnostic.span_err(item.span(), "alloc_error_handler must be a function");
+            ecx.sess.parse_sess.span_diagnostic.emit_err(errors::AllocErrorMustBeFn {span: item.span() });
             return vec![orig_item];
         };
 

compiler/rustc_builtin_macros/src/assert.rs

@@ -1,12 +1,13 @@
 mod context;
 
 use crate::edition_panic::use_panic_2021;
+use crate::errors;
 use rustc_ast::ptr::P;
 use rustc_ast::token;
 use rustc_ast::tokenstream::{DelimSpan, TokenStream};
 use rustc_ast::{DelimArgs, Expr, ExprKind, MacCall, MacDelimiter, Path, PathSegment, UnOp};
 use rustc_ast_pretty::pprust;
-use rustc_errors::{Applicability, PResult};
+use rustc_errors::PResult;
 use rustc_expand::base::{DummyResult, ExtCtxt, MacEager, MacResult};
 use rustc_parse::parser::Parser;
 use rustc_span::symbol::{sym, Ident, Symbol};
@@ -114,9 +115,7 @@ fn parse_assert<'a>(cx: &mut ExtCtxt<'a>, sp: Span, stream: TokenStream) -> PRes
     let mut parser = cx.new_parser_from_tts(stream);
 
     if parser.token == token::Eof {
-        let mut err = cx.struct_span_err(sp, "macro requires a boolean expression as an argument");
-        err.span_label(sp, "boolean expression required");
-        return Err(err);
+        return Err(cx.create_err(errors::AssertRequiresBoolean { span: sp }));
     }
 
     let cond_expr = parser.parse_expr()?;
@@ -129,15 +128,7 @@ fn parse_assert<'a>(cx: &mut ExtCtxt<'a>, sp: Span, stream: TokenStream) -> PRes
     //
     // Emit an error about semicolon and suggest removing it.
     if parser.token == token::Semi {
-        let mut err = cx.struct_span_err(sp, "macro requires an expression as an argument");
-        err.span_suggestion(
-            parser.token.span,
-            "try removing semicolon",
-            "",
-            Applicability::MaybeIncorrect,
-        );
-        err.emit();
-
+        cx.emit_err(errors::AssertRequiresExpression { span: sp, token: parser.token.span });
         parser.bump();
     }
 
@@ -149,15 +140,8 @@ fn parse_assert<'a>(cx: &mut ExtCtxt<'a>, sp: Span, stream: TokenStream) -> PRes
     // Emit an error and suggest inserting a comma.
     let custom_message =
         if let token::Literal(token::Lit { kind: token::Str, .. }) = parser.token.kind {
-            let mut err = cx.struct_span_err(parser.token.span, "unexpected string literal");
-            let comma_span = parser.prev_token.span.shrink_to_hi();
-            err.span_suggestion_short(
-                comma_span,
-                "try adding a comma",
-                ", ",
-                Applicability::MaybeIncorrect,
-            );
-            err.emit();
+            let comma = parser.prev_token.span.shrink_to_hi();
+            cx.emit_err(errors::AssertMissingComma { span: parser.token.span, comma });
 
             parse_custom_message(&mut parser)
         } else if parser.eat(&token::Comma) {

compiler/rustc_builtin_macros/src/cfg.rs

@@ -2,13 +2,13 @@
 //! a literal `true` or `false` based on whether the given cfg matches the
 //! current compilation environment.
 
+use crate::errors;
 use rustc_ast as ast;
 use rustc_ast::token;
 use rustc_ast::tokenstream::TokenStream;
 use rustc_attr as attr;
 use rustc_errors::PResult;
 use rustc_expand::base::{self, *};
-use rustc_macros::Diagnostic;
 use rustc_span::Span;
 
 pub fn expand_cfg(
@@ -35,34 +35,19 @@ pub fn expand_cfg(
     }
 }
 
-#[derive(Diagnostic)]
-#[diag(builtin_macros_requires_cfg_pattern)]
-struct RequiresCfgPattern {
-    #[primary_span]
-    #[label]
-    span: Span,
-}
-
-#[derive(Diagnostic)]
-#[diag(builtin_macros_expected_one_cfg_pattern)]
-struct OneCfgPattern {
-    #[primary_span]
-    span: Span,
-}
-
 fn parse_cfg<'a>(cx: &mut ExtCtxt<'a>, span: Span, tts: TokenStream) -> PResult<'a, ast::MetaItem> {
     let mut p = cx.new_parser_from_tts(tts);
 
     if p.token == token::Eof {
-        return Err(cx.create_err(RequiresCfgPattern { span }));
+        return Err(cx.create_err(errors::RequiresCfgPattern { span }));
     }
 
     let cfg = p.parse_meta_item()?;
 
     let _ = p.eat(&token::Comma);
 
     if !p.eat(&token::Eof) {
-        return Err(cx.create_err(OneCfgPattern { span }));
+        return Err(cx.create_err(errors::OneCfgPattern { span }));
     }
 
     Ok(cfg)

compiler/rustc_builtin_macros/src/cfg_accessible.rs

@@ -1,5 +1,6 @@
 //! Implementation of the `#[cfg_accessible(path)]` attribute macro.
 
+use crate::errors;
 use rustc_ast as ast;
 use rustc_expand::base::{Annotatable, ExpandResult, ExtCtxt, Indeterminate, MultiItemModifier};
 use rustc_feature::AttributeTemplate;
@@ -10,15 +11,22 @@ use rustc_span::Span;
 pub(crate) struct Expander;
 
 fn validate_input<'a>(ecx: &mut ExtCtxt<'_>, mi: &'a ast::MetaItem) -> Option<&'a ast::Path> {
+    use errors::CfgAccessibleInvalid::*;
     match mi.meta_item_list() {
         None => {}
-        Some([]) => ecx.span_err(mi.span, "`cfg_accessible` path is not specified"),
-        Some([_, .., l]) => ecx.span_err(l.span(), "multiple `cfg_accessible` paths are specified"),
+        Some([]) => {
+            ecx.emit_err(UnspecifiedPath(mi.span));
+        }
+        Some([_, .., l]) => {
+            ecx.emit_err(MultiplePaths(l.span()));
+        }
         Some([nmi]) => match nmi.meta_item() {
-            None => ecx.span_err(nmi.span(), "`cfg_accessible` path cannot be a literal"),
+            None => {
+                ecx.emit_err(LiteralPath(nmi.span()));
+            }
             Some(mi) => {
                 if !mi.is_word() {
-                    ecx.span_err(mi.span, "`cfg_accessible` path cannot accept arguments");
+                    ecx.emit_err(HasArguments(mi.span));
                 }
                 return Some(&mi.path);
             }
@@ -53,7 +61,7 @@ impl MultiItemModifier for Expander {
             Ok(true) => ExpandResult::Ready(vec![item]),
             Ok(false) => ExpandResult::Ready(Vec::new()),
             Err(Indeterminate) if ecx.force_mode => {
-                ecx.span_err(span, "cannot determine whether the path is accessible or not");
+                ecx.emit_err(errors::CfgAccessibleIndeterminate { span });
                 ExpandResult::Ready(vec![item])
             }
             Err(Indeterminate) => ExpandResult::Retry(item),

compiler/rustc_builtin_macros/src/compile_error.rs

@@ -13,6 +13,11 @@ pub fn expand_compile_error<'cx>(
         return DummyResult::any(sp);
     };
 
+    #[expect(
+        rustc::diagnostic_outside_of_impl,
+        reason = "diagnostic message is specified by user"
+    )]
+    #[expect(rustc::untranslatable_diagnostic, reason = "diagnostic message is specified by user")]
     cx.span_err(sp, var.as_str());
 
     DummyResult::any(sp)

compiler/rustc_builtin_macros/src/concat.rs

@@ -4,6 +4,8 @@ use rustc_expand::base::{self, DummyResult};
 use rustc_session::errors::report_lit_error;
 use rustc_span::symbol::Symbol;
 
+use crate::errors;
+
 pub fn expand_concat(
     cx: &mut base::ExtCtxt<'_>,
     sp: rustc_span::Span,
@@ -31,7 +33,7 @@ pub fn expand_concat(
                     accumulator.push_str(&b.to_string());
                 }
                 Ok(ast::LitKind::Byte(..) | ast::LitKind::ByteStr(..)) => {
-                    cx.span_err(e.span, "cannot concatenate a byte string literal");
+                    cx.emit_err(errors::ConcatBytestr { span: e.span });
                     has_errors = true;
                 }
                 Ok(ast::LitKind::Err) => {
@@ -55,7 +57,7 @@ pub fn expand_concat(
                 }
             }
             ast::ExprKind::IncludedBytes(..) => {
-                cx.span_err(e.span, "cannot concatenate a byte string literal")
+                cx.emit_err(errors::ConcatBytestr { span: e.span });
             }
             ast::ExprKind::Err => {
                 has_errors = true;
@@ -67,9 +69,7 @@ pub fn expand_concat(
     }
 
     if !missing_literal.is_empty() {
-        let mut err = cx.struct_span_err(missing_literal, "expected a literal");
-        err.note("only literals (like `\"foo\"`, `-42` and `3.14`) can be passed to `concat!()`");
-        err.emit();
+        cx.emit_err(errors::ConcatMissingLiteral { spans: missing_literal });
         return DummyResult::any(sp);
     } else if has_errors {
         return DummyResult::any(sp);