Move TokenDescription.

From the `parser` module to the `errors` module, which is where most of
its uses are.

This means the `errors` module no longer depends on the `parser` module,
removing a cyclic dependency between the two modules.

compiler/rustc_parse/src/errors.rs

@@ -3,7 +3,7 @@
 use std::borrow::Cow;
 use std::path::PathBuf;
 
-use rustc_ast::token::Token;
+use rustc_ast::token::{self, InvisibleOrigin, MetaVarKind, Token};
 use rustc_ast::util::parser::ExprPrecedence;
 use rustc_ast::{Path, Visibility};
 use rustc_errors::codes::*;
@@ -17,7 +17,6 @@
 use rustc_span::{Ident, Span, Symbol};
 
 use crate::fluent_generated as fluent;
-use crate::parser::TokenDescription;
 
 #[derive(Diagnostic)]
 #[diag(parse_maybe_report_ambiguous_plus)]
@@ -3735,3 +3734,32 @@ pub(crate) struct MisspelledKw {
     pub span: Span,
     pub is_incorrect_case: bool,
 }
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(super) enum TokenDescription {
+    ReservedIdentifier,
+    Keyword,
+    ReservedKeyword,
+    DocComment,
+
+    // Expanded metavariables are wrapped in invisible delimiters which aren't
+    // pretty-printed. In error messages we must handle these specially
+    // otherwise we get confusing things in messages like "expected `(`, found
+    // ``". It's better to say e.g. "expected `(`, found type metavariable".
+    MetaVar(MetaVarKind),
+}
+
+impl TokenDescription {
+    pub(super) fn from_token(token: &Token) -> Option<Self> {
+        match token.kind {
+            _ if token.is_special_ident() => Some(TokenDescription::ReservedIdentifier),
+            _ if token.is_used_keyword() => Some(TokenDescription::Keyword),
+            _ if token.is_unused_keyword() => Some(TokenDescription::ReservedKeyword),
+            token::DocComment(..) => Some(TokenDescription::DocComment),
+            token::OpenInvisible(InvisibleOrigin::MetaVar(kind)) => {
+                Some(TokenDescription::MetaVar(kind))
+            }
+            _ => None,
+        }
+    }
+}

compiler/rustc_parse/src/parser/mod.rs

@@ -49,7 +49,7 @@
 pub use token_type::{ExpKeywordPair, ExpTokenPair, TokenType};
 use tracing::debug;
 
-use crate::errors::{self, IncorrectVisibilityRestriction, NonStringAbiLiteral};
+use crate::errors::{self, IncorrectVisibilityRestriction, NonStringAbiLiteral, TokenDescription};
 use crate::exp;
 
 #[cfg(test)]
@@ -307,35 +307,6 @@ fn from(b: bool) -> Trailing {
     }
 }
 
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub(super) enum TokenDescription {
-    ReservedIdentifier,
-    Keyword,
-    ReservedKeyword,
-    DocComment,
-
-    // Expanded metavariables are wrapped in invisible delimiters which aren't
-    // pretty-printed. In error messages we must handle these specially
-    // otherwise we get confusing things in messages like "expected `(`, found
-    // ``". It's better to say e.g. "expected `(`, found type metavariable".
-    MetaVar(MetaVarKind),
-}
-
-impl TokenDescription {
-    pub(super) fn from_token(token: &Token) -> Option<Self> {
-        match token.kind {
-            _ if token.is_special_ident() => Some(TokenDescription::ReservedIdentifier),
-            _ if token.is_used_keyword() => Some(TokenDescription::Keyword),
-            _ if token.is_unused_keyword() => Some(TokenDescription::ReservedKeyword),
-            token::DocComment(..) => Some(TokenDescription::DocComment),
-            token::OpenInvisible(InvisibleOrigin::MetaVar(kind)) => {
-                Some(TokenDescription::MetaVar(kind))
-            }
-            _ => None,
-        }
-    }
-}
-
 pub fn token_descr(token: &Token) -> String {
     let s = pprust::token_to_string(token).to_string();