Moved structs to rustc_expand::errors, added several more migrations, fixed slug name

compiler/rustc_error_messages/locales/en-US/expand.ftl

@@ -10,5 +10,13 @@ expand_expr_repeat_no_syntax_vars =
 expand_must_repeat_once = 
     this must repeat at least once
 
-count_repetition_misplaced =
+expand_count_repetition_misplaced =
     `count` can not be placed inside the inner-most repetition
+
+expand_meta_var_expr_unrecognized_var =
+    variable `{$key}` is not recognized in meta-variable expression
+
+expand_var_still_repeating =
+    variable '{$ident}' is still repeating at this depth
+
+expand_meta_var_dif_seq_matchers = {$msg}

compiler/rustc_errors/src/diagnostic.rs

@@ -8,7 +8,7 @@ use rustc_error_messages::FluentValue;
 use rustc_hir as hir;
 use rustc_lint_defs::{Applicability, LintExpectationId};
 use rustc_span::edition::LATEST_STABLE_EDITION;
-use rustc_span::symbol::{Ident, Symbol};
+use rustc_span::symbol::{Ident, MacroRulesNormalizedIdent, Symbol};
 use rustc_span::{edition::Edition, Span, DUMMY_SP};
 use std::borrow::Cow;
 use std::fmt;
@@ -87,6 +87,7 @@ into_diagnostic_arg_using_display!(
     hir::Target,
     Edition,
     Ident,
+    MacroRulesNormalizedIdent,
 );
 
 impl IntoDiagnosticArg for bool {

compiler/rustc_expand/src/errors.rs

@@ -0,0 +1,50 @@
+use rustc_macros::SessionDiagnostic;
+use rustc_span::Span;
+use rustc_span::symbol::{MacroRulesNormalizedIdent};
+
+#[derive(SessionDiagnostic)]
+#[error(expand::expr_repeat_no_syntax_vars)]
+pub(crate) struct NoSyntaxVarsExprRepeat {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(expand::must_repeat_once)]
+pub(crate) struct MustRepeatOnce {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(expand::count_repetition_misplaced)]
+pub(crate) struct CountRepetitionMisplaced {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(expand::meta_var_expr_unrecognized_var)]
+pub(crate) struct MetaVarExprUnrecognizedVar {
+    #[primary_span]
+    pub span: Span,
+    pub key: MacroRulesNormalizedIdent,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(expand::var_still_repeating)]
+pub(crate) struct VarStillRepeating {
+    #[primary_span]
+    pub span: Span,
+    pub ident: MacroRulesNormalizedIdent,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(expand::var_still_repeating)]
+pub(crate) struct MetaVarsDifSeqMatchers {
+    #[primary_span]
+    pub span: Span,
+    pub msg: String,
+}
+
+

compiler/rustc_expand/src/lib.rs

@@ -25,6 +25,7 @@ pub mod base;
 pub mod build;
 #[macro_use]
 pub mod config;
+pub mod errors;
 pub mod expand;
 pub mod module;
 pub mod proc_macro;

compiler/rustc_expand/src/mbe/transcribe.rs

@@ -1,4 +1,8 @@
 use crate::base::ExtCtxt;
+use crate::errors::{
+    CountRepetitionMisplaced, MetaVarExprUnrecognizedVar, MetaVarsDifSeqMatchers, MustRepeatOnce,
+    NoSyntaxVarsExprRepeat, VarStillRepeating,
+};
 use crate::mbe::macro_parser::{MatchedNonterminal, MatchedSeq, MatchedTokenTree, NamedMatch};
 use crate::mbe::{self, MetaVarExpr};
 use rustc_ast::mut_visit::{self, MutVisitor};
@@ -7,7 +11,6 @@ use rustc_ast::tokenstream::{DelimSpan, Spacing, TokenStream, TokenTree};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{pluralize, PResult};
 use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed};
-use rustc_macros::SessionDiagnostic;
 use rustc_span::hygiene::{LocalExpnId, Transparency};
 use rustc_span::symbol::{sym, Ident, MacroRulesNormalizedIdent};
 use rustc_span::Span;
@@ -54,20 +57,6 @@ impl<'a> Iterator for Frame<'a> {
     }
 }
 
-#[derive(SessionDiagnostic)]
-#[error(expand::expr_repeat_no_syntax_vars)]
-struct NoSyntaxVarsExprRepeat {
-    #[primary_span]
-    span: Span,
-}
-
-#[derive(SessionDiagnostic)]
-#[error(expand::must_repeat_once)]
-struct MustRepeatOnce {
-    #[primary_span]
-    span: Span,
-}
-
 /// This can do Macro-By-Example transcription.
 /// - `interp` is a map of meta-variables to the tokens (non-terminals) they matched in the
 ///   invocation. We are assuming we already know there is a match.
@@ -188,7 +177,7 @@ pub(super) fn transcribe<'a>(
                         // happens when two meta-variables are used in the same repetition in a
                         // sequence, but they come from different sequence matchers and repeat
                         // different amounts.
-                        return Err(cx.struct_span_err(seq.span(), &msg));
+                        return Err(cx.create_err(MetaVarsDifSeqMatchers { span: seq.span(), msg }));
                     }
 
                     LockstepIterSize::Constraint(len, _) => {
@@ -247,10 +236,7 @@ pub(super) fn transcribe<'a>(
                         }
                         MatchedSeq(..) => {
                             // We were unable to descend far enough. This is an error.
-                            return Err(cx.struct_span_err(
+                            return Err(cx.create_err(VarStillRepeating { span: sp, ident }));
-                                sp, /* blame the macro writer */
-                                &format!("variable '{}' is still repeating at this depth", ident),
-                            ));
                         }
                     }
                 } else {
@@ -428,13 +414,6 @@ fn lockstep_iter_size(
     }
 }
 
-#[derive(SessionDiagnostic)]
-#[error(expand::count_repetition_misplaced)]
-struct CountRepetitionMisplaced {
-    #[primary_span]
-    span: Span,
-}
-
 /// Used solely by the `count` meta-variable expression, counts the outer-most repetitions at a
 /// given optional nested depth.
 ///
@@ -511,12 +490,7 @@ where
 {
     let span = ident.span;
     let key = MacroRulesNormalizedIdent::new(ident);
-    interp.get(&key).ok_or_else(|| {
+    interp.get(&key).ok_or_else(|| cx.create_err(MetaVarExprUnrecognizedVar { span, key }))
-        cx.struct_span_err(
-            span,
-            &format!("variable `{}` is not recognized in meta-variable expression", key),
-        )
-    })
 }
 
 /// Used by meta-variable expressions when an user input is out of the actual declared bounds. For