Rollup merge of #100651 - nidnogg:diagnostics_migration_expand_transcribe, r=davidtwco

Migrations for rustc_expand transcribe.rs

This PR includes some migrations to the new diagnostics API for the `rustc_expand` module.
r? ```@davidtwco```

5 files changed, 78 insertions, 25 deletions

diff --git a/compiler/rustc_error_messages/locales/en-US/expand.ftl b/compiler/rustc_error_messages/locales/en-US/expand.ftl
index bdfa22e77eb..ee76a4f4500 100644
--- a/compiler/rustc_error_messages/locales/en-US/expand.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/expand.ftl
@@ -3,3 +3,20 @@ expand_explain_doc_comment_outer =
 
 expand_explain_doc_comment_inner =
     inner doc comments expand to `#![doc = "..."]`, which is what this macro attempted to match
+
+expand_expr_repeat_no_syntax_vars = 
+    attempted to repeat an expression containing no syntax variables matched as repeating at this depth
+
+expand_must_repeat_once = 
+    this must repeat at least once
+
+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}
\ No newline at end of file
diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index 17e6c9e9575..356f9dfdb3b 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/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 {
diff --git a/compiler/rustc_expand/src/errors.rs b/compiler/rustc_expand/src/errors.rs
new file mode 100644
index 00000000000..0d7e137c7dd
--- /dev/null
+++ b/compiler/rustc_expand/src/errors.rs
@@ -0,0 +1,48 @@
+use rustc_macros::SessionDiagnostic;
+use rustc_span::symbol::MacroRulesNormalizedIdent;
+use rustc_span::Span;
+
+#[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::meta_var_dif_seq_matchers)]
+pub(crate) struct MetaVarsDifSeqMatchers {
+    #[primary_span]
+    pub span: Span,
+    pub msg: String,
+}
diff --git a/compiler/rustc_expand/src/lib.rs b/compiler/rustc_expand/src/lib.rs
index 91a18342784..e1dde1672c1 100644
--- a/compiler/rustc_expand/src/lib.rs
+++ b/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;
diff --git a/compiler/rustc_expand/src/mbe/transcribe.rs b/compiler/rustc_expand/src/mbe/transcribe.rs
index e47ea83ac38..bec6d1a2df7 100644
--- a/compiler/rustc_expand/src/mbe/transcribe.rs
+++ b/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};
@@ -165,11 +169,7 @@ pub(super) fn transcribe<'a>(
             seq @ mbe::TokenTree::Sequence(_, delimited) => {
                 match lockstep_iter_size(&seq, interp, &repeats) {
                     LockstepIterSize::Unconstrained => {
-                        return Err(cx.struct_span_err(
-                            seq.span(), /* blame macro writer */
-                            "attempted to repeat an expression containing no syntax variables \
-                             matched as repeating at this depth",
-                        ));
+                        return Err(cx.create_err(NoSyntaxVarsExprRepeat { span: seq.span() }));
                     }
 
                     LockstepIterSize::Contradiction(msg) => {
@@ -177,7 +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, _) => {
@@ -193,10 +193,7 @@ pub(super) fn transcribe<'a>(
                                 // FIXME: this really ought to be caught at macro definition
                                 // time... It happens when the Kleene operator in the matcher and
                                 // the body for the same meta-variable do not match.
-                                return Err(cx.struct_span_err(
-                                    sp.entire(),
-                                    "this must repeat at least once",
-                                ));
+                                return Err(cx.create_err(MustRepeatOnce { span: sp.entire() }));
                             }
                         } else {
                             // 0 is the initial counter (we have done 0 repetitions so far). `len`
@@ -239,10 +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(
-                                sp, /* blame the macro writer */
-                                &format!("variable '{}' is still repeating at this depth", ident),
-                            ));
+                            return Err(cx.create_err(VarStillRepeating { span: sp, ident }));
                         }
                     }
                 } else {
@@ -448,10 +442,7 @@ fn count_repetitions<'a>(
         match matched {
             MatchedTokenTree(_) | MatchedNonterminal(_) => {
                 if declared_lhs_depth == 0 {
-                    return Err(cx.struct_span_err(
-                        sp.entire(),
-                        "`count` can not be placed inside the inner-most repetition",
-                    ));
+                    return Err(cx.create_err(CountRepetitionMisplaced { span: sp.entire() }));
                 }
                 match depth_opt {
                     None => Ok(1),
@@ -499,12 +490,7 @@ where
 {
     let span = ident.span;
     let key = MacroRulesNormalizedIdent::new(ident);
-    interp.get(&key).ok_or_else(|| {
-        cx.struct_span_err(
-            span,
-            &format!("variable `{}` is not recognized in meta-variable expression", key),
-        )
-    })
+    interp.get(&key).ok_or_else(|| cx.create_err(MetaVarExprUnrecognizedVar { span, key }))
 }
 
 /// Used by meta-variable expressions when an user input is out of the actual declared bounds. For