refactor: refactor identifier parsing somewhat

compiler/rustc_parse/messages.ftl

@@ -336,7 +336,7 @@ parse_expected_identifier_found_reserved_keyword = expected identifier, found re
 parse_expected_identifier_found_doc_comment = expected identifier, found doc comment
 parse_expected_identifier = expected identifier
 
-parse_sugg_escape_to_use_as_identifier = escape `{$ident_name}` to use it as an identifier
+parse_sugg_escape_identifier = escape `{$ident_name}` to use it as an identifier
 
 parse_sugg_remove_comma = remove this comma
 

compiler/rustc_parse/src/errors.rs

@@ -888,12 +888,12 @@ pub(crate) struct InvalidMetaItem {
 
 #[derive(Subdiagnostic)]
 #[suggestion(
-    parse_sugg_escape_to_use_as_identifier,
+    parse_sugg_escape_identifier,
     style = "verbose",
     applicability = "maybe-incorrect",
     code = "r#"
 )]
-pub(crate) struct SuggEscapeToUseAsIdentifier {
+pub(crate) struct SuggEscapeIdentifier {
     #[primary_span]
     pub span: Span,
     pub ident_name: String,
@@ -937,7 +937,7 @@ impl ExpectedIdentifierFound {
 pub(crate) struct ExpectedIdentifier {
     pub span: Span,
     pub token: Token,
-    pub suggest_raw: Option<SuggEscapeToUseAsIdentifier>,
+    pub suggest_raw: Option<SuggEscapeIdentifier>,
     pub suggest_remove_comma: Option<SuggRemoveComma>,
     pub help_cannot_start_number: Option<HelpIdentifierStartsWithNumber>,
 }

compiler/rustc_parse/src/parser/diagnostics.rs

@@ -6,14 +6,14 @@ use super::{
 use crate::errors::{
     AmbiguousPlus, AttributeOnParamType, BadQPathStage2, BadTypePlus, BadTypePlusSub,
     ComparisonOperatorsCannotBeChained, ComparisonOperatorsCannotBeChainedSugg,
-    ConstGenericWithoutBraces, ConstGenericWithoutBracesSugg, DocCommentOnParamType,
-    DoubleColonInBound, ExpectedIdentifier, ExpectedSemi, ExpectedSemiSugg,
+    ConstGenericWithoutBraces, ConstGenericWithoutBracesSugg, DocCommentDoesNotDocumentAnything,
+    DocCommentOnParamType, DoubleColonInBound, ExpectedIdentifier, ExpectedSemi, ExpectedSemiSugg,
     GenericParamsWithoutAngleBrackets, GenericParamsWithoutAngleBracketsSugg,
     HelpIdentifierStartsWithNumber, InInTypo, IncorrectAwait, IncorrectSemicolon,
     IncorrectUseOfAwait, ParenthesesInForHead, ParenthesesInForHeadSugg,
     PatternMethodParamWithoutBody, QuestionMarkInType, QuestionMarkInTypeSugg, SelfParamNotFirst,
     StructLiteralBodyWithoutPath, StructLiteralBodyWithoutPathSugg, StructLiteralNeedingParens,
-    StructLiteralNeedingParensSugg, SuggEscapeToUseAsIdentifier, SuggRemoveComma,
+    StructLiteralNeedingParensSugg, SuggEscapeIdentifier, SuggRemoveComma,
     UnexpectedConstInGenericParam, UnexpectedConstParamDeclaration,
     UnexpectedConstParamDeclarationSugg, UnmatchedAngleBrackets, UseEqInstead,
 };
@@ -268,7 +268,16 @@ impl<'a> Parser<'a> {
         self.sess.source_map().span_to_snippet(span)
     }
 
+    /// Emits an error with suggestions if an identifier was expected but not found.
     pub(super) fn expected_ident_found(&mut self) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+        if let TokenKind::DocComment(..) = self.prev_token.kind {
+            return DocCommentDoesNotDocumentAnything {
+                span: self.prev_token.span,
+                missing_comma: None,
+            }
+            .into_diagnostic(&self.sess.span_diagnostic);
+        }
+
         let valid_follow = &[
             TokenKind::Eq,
             TokenKind::Colon,
@@ -286,7 +295,7 @@ impl<'a> Parser<'a> {
                 if ident.is_raw_guess()
                     && self.look_ahead(1, |t| valid_follow.contains(&t.kind)) =>
             {
-                Some(SuggEscapeToUseAsIdentifier {
+                Some(SuggEscapeIdentifier {
                     span: ident.span.shrink_to_lo(),
                     // `Symbol::to_string()` is different from `Symbol::into_diagnostic_arg()`,
                     // which uses `Symbol::to_ident_string()` and "helpfully" adds an implicit `r#`

compiler/rustc_parse/src/parser/item.rs

@@ -1744,7 +1744,7 @@ impl<'a> Parser<'a> {
     /// Parses a field identifier. Specialized version of `parse_ident_common`
     /// for better diagnostics and suggestions.
     fn parse_field_ident(&mut self, adt_ty: &str, lo: Span) -> PResult<'a, Ident> {
-        let (ident, is_raw) = self.ident_or_err()?;
+        let (ident, is_raw) = self.ident_or_err(true)?;
         if !is_raw && ident.is_reserved() {
             let snapshot = self.create_snapshot_for_diagnostic();
             let err = if self.check_fn_front_matter(false, Case::Sensitive) {

compiler/rustc_parse/src/parser/mod.rs

@@ -42,8 +42,7 @@ use thin_vec::ThinVec;
 use tracing::debug;
 
 use crate::errors::{
-    DocCommentDoesNotDocumentAnything, IncorrectVisibilityRestriction, MismatchedClosingDelimiter,
-    NonStringAbiLiteral,
+    IncorrectVisibilityRestriction, MismatchedClosingDelimiter, NonStringAbiLiteral,
 };
 
 bitflags::bitflags! {
@@ -552,19 +551,8 @@ impl<'a> Parser<'a> {
         self.parse_ident_common(true)
     }
 
-    fn ident_or_err(&mut self) -> PResult<'a, (Ident, /* is_raw */ bool)> {
-        self.token.ident().ok_or_else(|| match self.prev_token.kind {
-            TokenKind::DocComment(..) => DocCommentDoesNotDocumentAnything {
-                span: self.prev_token.span,
-                missing_comma: None,
-            }
-            .into_diagnostic(&self.sess.span_diagnostic),
-            _ => self.expected_ident_found(),
-        })
-    }
-
     fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, Ident> {
-        let (ident, is_raw) = self.ident_or_err()?;
+        let (ident, is_raw) = self.ident_or_err(recover)?;
         if !is_raw && ident.is_reserved() {
             let mut err = self.expected_ident_found();
             if recover {
@@ -577,6 +565,17 @@ impl<'a> Parser<'a> {
         Ok(ident)
     }
 
+    fn ident_or_err(&mut self, _recover: bool) -> PResult<'a, (Ident, /* is_raw */ bool)> {
+        let result = self.token.ident().ok_or_else(|| self.expected_ident_found());
+
+        let (ident, is_raw) = match result {
+            Ok(ident) => ident,
+            Err(err) => return Err(err),
+        };
+
+        Ok((ident, is_raw))
+    }
+
     /// Checks if the next token is `tok`, and returns `true` if so.
     ///
     /// This method will automatically add `tok` to `expected_tokens` if `tok` is not