Rollup merge of #123462 - fmease:rn-mod-sep-to-path-sep, r=nnethercote

Cleanup: Rename `ModSep` to `PathSep`

`::` is usually referred to as the *path separator* (citation needed).

The existing name `ModSep` for *module separator* is a bit misleading since it in fact separates the segments of arbitrary path segments, not only ones resolving to modules. Let me just give a shout-out to associated items (`T::Assoc`, `<Ty as Trait>::function`) and enum variants (`Option::None`).

Motivation: Reduce friction for new contributors, prevent potential confusion.

cc `@petrochenkov`
r? nnethercote or compiler

compiler/rustc_ast/src/attr/mod.rs

@@ -308,11 +308,11 @@ fn from_tokens<'a, I>(tokens: &mut iter::Peekable<I>) -> Option<MetaItem>
         // FIXME: Share code with `parse_path`.
         let path = match tokens.next().map(|tt| TokenTree::uninterpolate(tt)).as_deref() {
             Some(&TokenTree::Token(
-                Token { kind: ref kind @ (token::Ident(..) | token::ModSep), span },
+                Token { kind: ref kind @ (token::Ident(..) | token::PathSep), span },
                 _,
             )) => 'arm: {
                 let mut segments = if let &token::Ident(name, _) = kind {
-                    if let Some(TokenTree::Token(Token { kind: token::ModSep, .. }, _)) =
+                    if let Some(TokenTree::Token(Token { kind: token::PathSep, .. }, _)) =
                         tokens.peek()
                     {
                         tokens.next();
@@ -331,7 +331,7 @@ fn from_tokens<'a, I>(tokens: &mut iter::Peekable<I>) -> Option<MetaItem>
                     } else {
                         return None;
                     }
-                    if let Some(TokenTree::Token(Token { kind: token::ModSep, .. }, _)) =
+                    if let Some(TokenTree::Token(Token { kind: token::PathSep, .. }, _)) =
                         tokens.peek()
                     {
                         tokens.next();

compiler/rustc_ast/src/token.rs

@@ -290,7 +290,7 @@ pub enum TokenKind {
     /// `:`
     Colon,
     /// `::`
-    ModSep,
+    PathSep,
     /// `->`
     RArrow,
     /// `<-`
@@ -393,7 +393,7 @@ pub fn break_two_token_op(&self) -> Option<(TokenKind, TokenKind)> {
             BinOpEq(Shr) => (Gt, Ge),
             DotDot => (Dot, Dot),
             DotDotDot => (Dot, DotDot),
-            ModSep => (Colon, Colon),
+            PathSep => (Colon, Colon),
             RArrow => (BinOp(Minus), Gt),
             LArrow => (Lt, BinOp(Minus)),
             FatArrow => (Eq, Gt),
@@ -454,7 +454,9 @@ pub fn is_punct(&self) -> bool {
         match self.kind {
             Eq | Lt | Le | EqEq | Ne | Ge | Gt | AndAnd | OrOr | Not | Tilde | BinOp(_)
             | BinOpEq(_) | At | Dot | DotDot | DotDotDot | DotDotEq | Comma | Semi | Colon
-            | ModSep | RArrow | LArrow | FatArrow | Pound | Dollar | Question | SingleQuote => true,
+            | PathSep | RArrow | LArrow | FatArrow | Pound | Dollar | Question | SingleQuote => {
+                true
+            }
 
             OpenDelim(..) | CloseDelim(..) | Literal(..) | DocComment(..) | Ident(..)
             | Lifetime(..) | Interpolated(..) | Eof => false,
@@ -481,7 +483,7 @@ pub fn can_begin_expr(&self) -> bool {
             // DotDotDot is no longer supported, but we need some way to display the error
             DotDot | DotDotDot | DotDotEq     | // range notation
             Lt | BinOp(Shl)                   | // associated path
-            ModSep                            | // global path
+            PathSep                            | // global path
             Lifetime(..)                      | // labeled loop
             Pound                             => true, // expression attributes
             Interpolated(ref nt) => matches!(&nt.0, NtLiteral(..) |
@@ -507,7 +509,7 @@ pub fn can_begin_pattern(&self) -> bool {
             // DotDotDot is no longer supported
             | DotDot | DotDotDot | DotDotEq      // ranges
             | Lt | BinOp(Shl)                    // associated path
-            | ModSep                    => true, // global path
+            | PathSep                    => true, // global path
             Interpolated(ref nt) => matches!(&nt.0, NtLiteral(..) |
                 NtPat(..)     |
                 NtBlock(..)   |
@@ -530,7 +532,7 @@ pub fn can_begin_type(&self) -> bool {
             Question                    | // maybe bound in trait object
             Lifetime(..)                | // lifetime bound in trait object
             Lt | BinOp(Shl)             | // associated path
-            ModSep                      => true, // global path
+            PathSep                      => true, // global path
             Interpolated(ref nt) => matches!(&nt.0, NtTy(..) | NtPath(..)),
             // For anonymous structs or unions, which only appear in specific positions
             // (type of struct fields or union fields), we don't consider them as regular types
@@ -708,7 +710,7 @@ pub fn is_qpath_start(&self) -> bool {
     }
 
     pub fn is_path_start(&self) -> bool {
-        self == &ModSep
+        self == &PathSep
             || self.is_qpath_start()
             || self.is_whole_path()
             || self.is_path_segment_keyword()
@@ -821,7 +823,7 @@ pub fn glue(&self, joint: &Token) -> Option<Token> {
                 _ => return None,
             },
             Colon => match joint.kind {
-                Colon => ModSep,
+                Colon => PathSep,
                 _ => return None,
             },
             SingleQuote => match joint.kind {
@@ -830,7 +832,7 @@ pub fn glue(&self, joint: &Token) -> Option<Token> {
             },
 
             Le | EqEq | Ne | Ge | AndAnd | OrOr | Tilde | BinOpEq(..) | At | DotDotDot
-            | DotDotEq | Comma | Semi | ModSep | RArrow | LArrow | FatArrow | Pound | Dollar
+            | DotDotEq | Comma | Semi | PathSep | RArrow | LArrow | FatArrow | Pound | Dollar
             | Question | OpenDelim(..) | CloseDelim(..) | Literal(..) | Ident(..)
             | Lifetime(..) | Interpolated(..) | DocComment(..) | Eof => return None,
         };

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -893,7 +893,7 @@ fn token_kind_to_string_ext(
             token::Comma => ",".into(),
             token::Semi => ";".into(),
             token::Colon => ":".into(),
-            token::ModSep => "::".into(),
+            token::PathSep => "::".into(),
             token::RArrow => "->".into(),
             token::LArrow => "<-".into(),
             token::FatArrow => "=>".into(),

compiler/rustc_expand/src/proc_macro_server.rs

@@ -208,7 +208,7 @@ fn from_internal((stream, rustc): (TokenStream, &mut Rustc<'_, '_>)) -> Self {
                 Comma => op(","),
                 Semi => op(";"),
                 Colon => op(":"),
-                ModSep => op("::"),
+                PathSep => op("::"),
                 RArrow => op("->"),
                 LArrow => op("<-"),
                 FatArrow => op("=>"),

compiler/rustc_parse/src/parser/diagnostics.rs

@@ -279,7 +279,7 @@ pub(super) fn expected_ident_found(
             TokenKind::Colon,
             TokenKind::Comma,
             TokenKind::Semi,
-            TokenKind::ModSep,
+            TokenKind::PathSep,
             TokenKind::OpenDelim(Delimiter::Brace),
             TokenKind::OpenDelim(Delimiter::Parenthesis),
             TokenKind::CloseDelim(Delimiter::Brace),
@@ -1169,7 +1169,7 @@ pub(super) fn check_turbofish_missing_angle_brackets(&mut self, segment: &mut Pa
             return;
         }
 
-        if token::ModSep == self.token.kind && segment.args.is_none() {
+        if token::PathSep == self.token.kind && segment.args.is_none() {
             let snapshot = self.create_snapshot_for_diagnostic();
             self.bump();
             let lo = self.token.span;
@@ -1420,7 +1420,7 @@ pub(super) fn check_no_chained_comparison(
                             [(token::Lt, 1), (token::Gt, -1), (token::BinOp(token::Shr), -2)];
                         self.consume_tts(1, &modifiers);
 
-                        if !&[token::OpenDelim(Delimiter::Parenthesis), token::ModSep]
+                        if !&[token::OpenDelim(Delimiter::Parenthesis), token::PathSep]
                             .contains(&self.token.kind)
                         {
                             // We don't have `foo< bar >(` or `foo< bar >::`, so we rewind the
@@ -1428,7 +1428,7 @@ pub(super) fn check_no_chained_comparison(
                             self.restore_snapshot(snapshot);
                         }
                     }
-                    return if token::ModSep == self.token.kind {
+                    return if token::PathSep == self.token.kind {
                         // We have some certainty that this was a bad turbofish at this point.
                         // `foo< bar >::`
                         if let ExprKind::Binary(o, ..) = inner_op.kind
@@ -1784,7 +1784,7 @@ pub(super) fn maybe_recover_from_bad_qpath<T: RecoverQPath>(
         }
 
         // Do not add `::` to expected tokens.
-        if self.token == token::ModSep {
+        if self.token == token::PathSep {
             if let Some(ty) = base.to_ty() {
                 return self.maybe_recover_from_bad_qpath_stage_2(ty.span, ty);
             }
@@ -1799,7 +1799,7 @@ pub(super) fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(
         ty_span: Span,
         ty: P<Ty>,
     ) -> PResult<'a, P<T>> {
-        self.expect(&token::ModSep)?;
+        self.expect(&token::PathSep)?;
 
         let mut path = ast::Path { segments: ThinVec::new(), span: DUMMY_SP, tokens: None };
         self.parse_path_segments(&mut path.segments, T::PATH_STYLE, None)?;

compiler/rustc_parse/src/parser/item.rs

@@ -358,12 +358,12 @@ pub(super) fn is_path_start_item(&mut self) -> bool {
     fn is_reuse_path_item(&mut self) -> bool {
         // no: `reuse ::path` for compatibility reasons with macro invocations
         self.token.is_keyword(kw::Reuse)
-            && self.look_ahead(1, |t| t.is_path_start() && t.kind != token::ModSep)
+            && self.look_ahead(1, |t| t.is_path_start() && t.kind != token::PathSep)
     }
 
     /// Are we sure this could not possibly be a macro invocation?
     fn isnt_macro_invocation(&mut self) -> bool {
-        self.check_ident() && self.look_ahead(1, |t| *t != token::Not && *t != token::ModSep)
+        self.check_ident() && self.look_ahead(1, |t| *t != token::Not && *t != token::PathSep)
     }
 
     /// Recover on encountering a struct or method definition where the user
@@ -1020,7 +1020,7 @@ fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
         {
             // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
             let mod_sep_ctxt = self.token.span.ctxt();
-            if self.eat(&token::ModSep) {
+            if self.eat(&token::PathSep) {
                 prefix
                     .segments
                     .push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
@@ -1031,7 +1031,7 @@ fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
             // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
             prefix = self.parse_path(PathStyle::Mod)?;
 
-            if self.eat(&token::ModSep) {
+            if self.eat(&token::PathSep) {
                 self.parse_use_tree_glob_or_nested()?
             } else {
                 // Recover from using a colon as path separator.
@@ -2752,7 +2752,7 @@ fn parse_self_param(&mut self) -> PResult<'a, Option<Param>> {
         // Is `self` `n` tokens ahead?
         let is_isolated_self = |this: &Self, n| {
             this.is_keyword_ahead(n, &[kw::SelfLower])
-                && this.look_ahead(n + 1, |t| t != &token::ModSep)
+                && this.look_ahead(n + 1, |t| t != &token::PathSep)
         };
         // Is `mut self` `n` tokens ahead?
         let is_isolated_mut_self =

compiler/rustc_parse/src/parser/mod.rs

@@ -109,7 +109,7 @@ macro_rules! maybe_recover_from_interpolated_ty_qpath {
     ($self: expr, $allow_qpath_recovery: expr) => {
         if $allow_qpath_recovery
             && $self.may_recover()
-            && $self.look_ahead(1, |t| t == &token::ModSep)
+            && $self.look_ahead(1, |t| t == &token::PathSep)
             && let token::Interpolated(nt) = &$self.token.kind
             && let token::NtTy(ty) = &nt.0
         {
@@ -1532,7 +1532,7 @@ pub fn collect_tokens_no_attrs<R: HasAttrs + HasTokens>(
 
     /// `::{` or `::*`
     fn is_import_coupler(&mut self) -> bool {
-        self.check(&token::ModSep)
+        self.check(&token::PathSep)
             && self.look_ahead(1, |t| {
                 *t == token::OpenDelim(Delimiter::Brace) || *t == token::BinOp(token::Star)
             })

compiler/rustc_parse/src/parser/nonterminal.rs

@@ -62,7 +62,7 @@ fn may_be_ident(nt: &token::Nonterminal) -> bool {
                 _ => false,
             },
             NonterminalKind::Path | NonterminalKind::Meta => match &token.kind {
-                token::ModSep | token::Ident(..) => true,
+                token::PathSep | token::Ident(..) => true,
                 token::Interpolated(nt) => may_be_ident(&nt.0),
                 _ => false,
             },
@@ -76,7 +76,7 @@ fn may_be_ident(nt: &token::Nonterminal) -> bool {
                 token::Literal(_) |                         // literal
                 token::DotDot |                             // range pattern (future compat)
                 token::DotDotDot |                          // range pattern (future compat)
-                token::ModSep |                             // path
+                token::PathSep |                             // path
                 token::Lt |                                 // path (UFCS constant)
                 token::BinOp(token::Shl) => true,           // path (double UFCS)
                 // leading vert `|` or-pattern

compiler/rustc_parse/src/parser/pat.rs

@@ -1016,7 +1016,7 @@ fn can_be_ident_pat(&mut self) -> bool {
         && self.look_ahead(1, |t| !matches!(t.kind, token::OpenDelim(Delimiter::Parenthesis) // A tuple struct pattern.
             | token::OpenDelim(Delimiter::Brace) // A struct pattern.
             | token::DotDotDot | token::DotDotEq | token::DotDot // A range pattern.
-            | token::ModSep // A tuple / struct variant pattern.
+            | token::PathSep // A tuple / struct variant pattern.
             | token::Not)) // A macro expanding to a pattern.
     }
 

compiler/rustc_parse/src/parser/path.rs

@@ -96,7 +96,7 @@ pub(super) fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (P<QSelf>,
         }
 
         if !self.recover_colon_before_qpath_proj() {
-            self.expect(&token::ModSep)?;
+            self.expect(&token::PathSep)?;
         }
 
         let qself = P(QSelf { ty, path_span, position: path.segments.len() });
@@ -200,7 +200,7 @@ pub(super) fn parse_path_inner(
         let lo = self.token.span;
         let mut segments = ThinVec::new();
         let mod_sep_ctxt = self.token.span.ctxt();
-        if self.eat(&token::ModSep) {
+        if self.eat(&token::PathSep) {
             segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
         }
         self.parse_path_segments(&mut segments, style, ty_generics)?;
@@ -232,11 +232,11 @@ pub(super) fn parse_path_segments(
                 // `PathStyle::Expr` is only provided at the root invocation and never in
                 // `parse_path_segment` to recurse and therefore can be checked to maintain
                 // this invariant.
-                self.check_trailing_angle_brackets(&segment, &[&token::ModSep]);
+                self.check_trailing_angle_brackets(&segment, &[&token::PathSep]);
             }
             segments.push(segment);
 
-            if self.is_import_coupler() || !self.eat(&token::ModSep) {
+            if self.is_import_coupler() || !self.eat(&token::PathSep) {
                 if style == PathStyle::Expr
                     && self.may_recover()
                     && self.token == token::Colon
@@ -291,7 +291,7 @@ pub(super) fn parse_path_segment(
         Ok(
             if style == PathStyle::Type && check_args_start(self)
                 || style != PathStyle::Mod
-                    && self.check(&token::ModSep)
+                    && self.check(&token::PathSep)
                     && self.look_ahead(1, |t| is_args_start(t))
             {
                 // We use `style == PathStyle::Expr` to check if this is in a recursion or not. If
@@ -303,7 +303,7 @@ pub(super) fn parse_path_segment(
                 }
 
                 // Generic arguments are found - `<`, `(`, `::<` or `::(`.
-                self.eat(&token::ModSep);
+                self.eat(&token::PathSep);
                 let lo = self.token.span;
                 let args = if self.eat_lt() {
                     // `<'a, T, A = U>`
@@ -379,7 +379,7 @@ pub(super) fn parse_path_segment(
                     let token_before_parsing = self.token.clone();
                     let mut snapshot = None;
                     if self.may_recover()
-                        && prev_token_before_parsing.kind == token::ModSep
+                        && prev_token_before_parsing.kind == token::PathSep
                         && (style == PathStyle::Expr && self.token.can_begin_expr()
                             || style == PathStyle::Pat && self.token.can_begin_pattern())
                     {
@@ -388,7 +388,7 @@ pub(super) fn parse_path_segment(
 
                     let (inputs, _) = match self.parse_paren_comma_seq(|p| p.parse_ty()) {
                         Ok(output) => output,
-                        Err(mut error) if prev_token_before_parsing.kind == token::ModSep => {
+                        Err(mut error) if prev_token_before_parsing.kind == token::PathSep => {
                             error.span_label(
                                 prev_token_before_parsing.span.to(token_before_parsing.span),
                                 "while parsing this parenthesized list of type arguments starting here",
@@ -470,7 +470,7 @@ fn recover_fn_call_leading_path_sep(
             }
         }
 
-        if let token::ModSep | token::RArrow = self.token.kind {
+        if let token::PathSep | token::RArrow = self.token.kind {
             return;
         }
 

compiler/rustc_parse/src/parser/ty.rs

@@ -82,7 +82,7 @@ enum AllowCVariadic {
 /// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
 /// that `IDENT` is not the ident of a fn trait.
 fn can_continue_type_after_non_fn_ident(t: &Token) -> bool {
-    t == &token::ModSep || t == &token::Lt || t == &token::BinOp(token::Shl)
+    t == &token::PathSep || t == &token::Lt || t == &token::BinOp(token::Shl)
 }
 
 fn can_begin_dyn_bound_in_edition_2015(t: &Token) -> bool {

src/tools/clippy/clippy_lints/src/crate_in_macro_def.rs

@@ -88,7 +88,7 @@ fn contains_unhygienic_crate_reference(tts: &TokenStream) -> Option<Span> {
         if !prev_is_dollar
             && let Some(span) = is_crate_keyword(curr)
             && let Some(next) = cursor.look_ahead(0)
-            && is_token(next, &TokenKind::ModSep)
+            && is_token(next, &TokenKind::PathSep)
         {
             return Some(span);
         }

src/tools/rustfmt/src/macros.rs

@@ -1091,7 +1091,7 @@ fn next_space(tok: &TokenKind) -> SpaceState {
         | TokenKind::DotDotEq
         | TokenKind::Question => SpaceState::Punctuation,
 
-        TokenKind::ModSep
+        TokenKind::PathSep
         | TokenKind::Pound
         | TokenKind::Dollar
         | TokenKind::OpenDelim(_)