Remove TrailingToken.

It's used in `Parser::collect_tokens_trailing_token` to decide whether
to capture a trailing token. But the callers actually know whether to
capture a trailing token, so it's simpler for them to just pass in a
bool.

Also, the `TrailingToken::Gt` case was weird, because it didn't result
in a trailing token being captured. It could have been subsumed by the
`TrailingToken::MaybeComma` case, and it effectively is in the new code.

Author: nnethercote

compiler/rustc_parse/src/parser/attr_wrapper.rs

@@ -1,5 +1,5 @@
-use super::{Capturing, FlatToken, ForceCollect, Parser, ReplaceRange, TokenCursor, TrailingToken};
-use rustc_ast::token::{self, Delimiter, Token, TokenKind};
+use super::{Capturing, FlatToken, ForceCollect, Parser, ReplaceRange, TokenCursor};
+use rustc_ast::token::{Delimiter, Token, TokenKind};
 use rustc_ast::tokenstream::{AttrTokenStream, AttrTokenTree, AttrsTarget, DelimSpacing};
 use rustc_ast::tokenstream::{DelimSpan, LazyAttrTokenStream, Spacing, ToAttrTokenStream};
 use rustc_ast::{self as ast};
@@ -165,8 +165,10 @@ impl ToAttrTokenStream for LazyAttrTokenStreamImpl {
 impl<'a> Parser<'a> {
     /// Records all tokens consumed by the provided callback,
     /// including the current token. These tokens are collected
-    /// into a `LazyAttrTokenStream`, and returned along with the result
-    /// of the callback.
+    /// into a `LazyAttrTokenStream`, and returned along with the first part of
+    /// the callback's result. The second (bool) part of the callback's result
+    /// indicates if an extra token should be captured, e.g. a comma or
+    /// semicolon.
     ///
     /// The `attrs` passed in are in `AttrWrapper` form, which is opaque. The
     /// `AttrVec` within is passed to `f`. See the comment on `AttrWrapper` for
@@ -187,7 +189,7 @@ impl<'a> Parser<'a> {
         &mut self,
         attrs: AttrWrapper,
         force_collect: ForceCollect,
-        f: impl FnOnce(&mut Self, ast::AttrVec) -> PResult<'a, (R, TrailingToken)>,
+        f: impl FnOnce(&mut Self, ast::AttrVec) -> PResult<'a, (R, bool)>,
     ) -> PResult<'a, R> {
         // We only bail out when nothing could possibly observe the collected tokens:
         // 1. We cannot be force collecting tokens (since force-collecting requires tokens
@@ -212,7 +214,7 @@ impl<'a> Parser<'a> {
         let has_outer_attrs = !attrs.attrs.is_empty();
         let replace_ranges_start = self.capture_state.replace_ranges.len();
 
-        let (mut ret, trailing) = {
+        let (mut ret, capture_trailing) = {
             let prev_capturing = mem::replace(&mut self.capture_state.capturing, Capturing::Yes);
             let ret_and_trailing = f(self, attrs.attrs);
             self.capture_state.capturing = prev_capturing;
@@ -266,27 +268,13 @@ impl<'a> Parser<'a> {
 
         let replace_ranges_end = self.capture_state.replace_ranges.len();
 
-        // Capture a trailing token if requested by the callback 'f'
-        let captured_trailing = match trailing {
-            TrailingToken::None => false,
-            TrailingToken::Gt => {
-                assert_eq!(self.token.kind, token::Gt);
-                false
-            }
-            TrailingToken::Semi => {
-                assert_eq!(self.token.kind, token::Semi);
-                true
-            }
-            TrailingToken::MaybeComma => self.token.kind == token::Comma,
-        };
-
         assert!(
-            !(self.break_last_token && captured_trailing),
+            !(self.break_last_token && capture_trailing),
             "Cannot set break_last_token and have trailing token"
         );
 
         let end_pos = self.num_bump_calls
-            + captured_trailing as u32
+            + capture_trailing as u32
             // If we 'broke' the last token (e.g. breaking a '>>' token to two '>' tokens), then
             // extend the range of captured tokens to include it, since the parser was not actually
             // bumped past it. When the `LazyAttrTokenStream` gets converted into an

compiler/rustc_parse/src/parser/expr.rs

@@ -5,7 +5,7 @@ use super::pat::{CommaRecoveryMode, Expected, RecoverColon, RecoverComma};
 use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
 use super::{
     AttrWrapper, BlockMode, ClosureSpans, ForceCollect, Parser, PathStyle, Restrictions,
-    SemiColonMode, SeqSep, TokenType, Trailing, TrailingToken,
+    SemiColonMode, SeqSep, TokenType, Trailing,
 };
 
 use crate::errors;
@@ -2486,7 +2486,7 @@ impl<'a> Parser<'a> {
                     id: DUMMY_NODE_ID,
                     is_placeholder: false,
                 },
-                TrailingToken::MaybeComma,
+                this.token == token::Comma,
             ))
         })
     }
@@ -3262,7 +3262,7 @@ impl<'a> Parser<'a> {
                     id: DUMMY_NODE_ID,
                     is_placeholder: false,
                 },
-                TrailingToken::None,
+                false,
             ))
         })
     }
@@ -3771,7 +3771,7 @@ impl<'a> Parser<'a> {
                     id: DUMMY_NODE_ID,
                     is_placeholder: false,
                 },
-                TrailingToken::MaybeComma,
+                false,
             ))
         })
     }
@@ -3867,18 +3867,12 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, P<Expr>> {
         self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
             let res = f(this, attrs)?;
-            let trailing = if this.restrictions.contains(Restrictions::STMT_EXPR)
-                && this.token.kind == token::Semi
-            {
-                TrailingToken::Semi
-            } else if this.token.kind == token::Gt {
-                TrailingToken::Gt
-            } else {
-                // FIXME - pass this through from the place where we know
-                // we need a comma, rather than assuming that `#[attr] expr,`
-                // always captures a trailing comma
-                TrailingToken::MaybeComma
-            };
+            let trailing = (this.restrictions.contains(Restrictions::STMT_EXPR)
+                 && this.token.kind == token::Semi)
+            // FIXME: pass an additional condition through from the place
+            // where we know we need a comma, rather than assuming that
+            // `#[attr] expr,` always captures a trailing comma.
+            || this.token.kind == token::Comma;
             Ok((res, trailing))
         })
     }

compiler/rustc_parse/src/parser/generics.rs

@@ -4,7 +4,7 @@ use crate::errors::{
     WhereClauseBeforeTupleStructBodySugg,
 };
 
-use super::{ForceCollect, Parser, TrailingToken};
+use super::{ForceCollect, Parser};
 
 use ast::token::Delimiter;
 use rustc_ast::token;
@@ -229,13 +229,13 @@ impl<'a> Parser<'a> {
                                     span: where_predicate.span(),
                                 });
                                 // FIXME - try to continue parsing other generics?
-                                return Ok((None, TrailingToken::None));
+                                return Ok((None, false));
                             }
                             Err(err) => {
                                 err.cancel();
                                 // FIXME - maybe we should overwrite 'self' outside of `collect_tokens`?
                                 this.restore_snapshot(snapshot);
-                                return Ok((None, TrailingToken::None));
+                                return Ok((None, false));
                             }
                         }
                     } else {
@@ -249,14 +249,14 @@ impl<'a> Parser<'a> {
                                     .emit_err(errors::AttrWithoutGenerics { span: attrs[0].span });
                             }
                         }
-                        return Ok((None, TrailingToken::None));
+                        return Ok((None, false));
                     };
 
                     if !this.eat(&token::Comma) {
                         done = true;
                     }
-                    // We just ate the comma, so no need to use `TrailingToken`
-                    Ok((param, TrailingToken::None))
+                    // We just ate the comma, so no need to capture the trailing token.
+                    Ok((param, false))
                 })?;
 
             if let Some(param) = param {

compiler/rustc_parse/src/parser/item.rs

@@ -1,8 +1,6 @@
 use super::diagnostics::{dummy_arg, ConsumeClosingDelim};
 use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
-use super::{
-    AttrWrapper, FollowedByType, ForceCollect, Parser, PathStyle, Trailing, TrailingToken,
-};
+use super::{AttrWrapper, FollowedByType, ForceCollect, Parser, PathStyle, Trailing};
 use crate::errors::{self, MacroExpandsToAdtField};
 use crate::fluent_generated as fluent;
 use crate::maybe_whole;
@@ -132,7 +130,7 @@ impl<'a> Parser<'a> {
             self.collect_tokens_trailing_token(attrs, force_collect, |this: &mut Self, attrs| {
                 let item =
                     this.parse_item_common_(attrs, mac_allowed, attrs_allowed, fn_parse_mode);
-                Ok((item?, TrailingToken::None))
+                Ok((item?, false))
             })?;
 
         Ok(item)
@@ -1570,7 +1568,7 @@ impl<'a> Parser<'a> {
 
                 let vis = this.parse_visibility(FollowedByType::No)?;
                 if !this.recover_nested_adt_item(kw::Enum)? {
-                    return Ok((None, TrailingToken::None));
+                    return Ok((None, false));
                 }
                 let ident = this.parse_field_ident("enum", vlo)?;
 
@@ -1582,7 +1580,7 @@ impl<'a> Parser<'a> {
                     this.bump();
                     this.parse_delim_args()?;
 
-                    return Ok((None, TrailingToken::MaybeComma));
+                    return Ok((None, this.token == token::Comma));
                 }
 
                 let struct_def = if this.check(&token::OpenDelim(Delimiter::Brace)) {
@@ -1639,7 +1637,7 @@ impl<'a> Parser<'a> {
                     is_placeholder: false,
                 };
 
-                Ok((Some(vr), TrailingToken::MaybeComma))
+                Ok((Some(vr), this.token == token::Comma))
             },
         )
         .map_err(|mut err| {
@@ -1831,7 +1829,7 @@ impl<'a> Parser<'a> {
                         attrs,
                         is_placeholder: false,
                     },
-                    TrailingToken::MaybeComma,
+                    p.token == token::Comma,
                 ))
             })
         })
@@ -1846,8 +1844,7 @@ impl<'a> Parser<'a> {
         self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
             let lo = this.token.span;
             let vis = this.parse_visibility(FollowedByType::No)?;
-            this.parse_single_struct_field(adt_ty, lo, vis, attrs)
-                .map(|field| (field, TrailingToken::None))
+            this.parse_single_struct_field(adt_ty, lo, vis, attrs).map(|field| (field, false))
         })
     }
 
@@ -2746,7 +2743,7 @@ impl<'a> Parser<'a> {
             if let Some(mut param) = this.parse_self_param()? {
                 param.attrs = attrs;
                 let res = if first_param { Ok(param) } else { this.recover_bad_self_param(param) };
-                return Ok((res?, TrailingToken::None));
+                return Ok((res?, false));
             }
 
             let is_name_required = match this.token.kind {
@@ -2762,7 +2759,7 @@ impl<'a> Parser<'a> {
                         this.parameter_without_type(&mut err, pat, is_name_required, first_param)
                     {
                         let guar = err.emit();
-                        Ok((dummy_arg(ident, guar), TrailingToken::None))
+                        Ok((dummy_arg(ident, guar), false))
                     } else {
                         Err(err)
                     };
@@ -2805,7 +2802,7 @@ impl<'a> Parser<'a> {
 
             Ok((
                 Param { attrs, id: ast::DUMMY_NODE_ID, is_placeholder: false, pat, span, ty },
-                TrailingToken::None,
+                false,
             ))
         })
     }

compiler/rustc_parse/src/parser/mod.rs

@@ -91,16 +91,6 @@ pub enum ForceCollect {
     No,
 }
 
-#[derive(Debug, Eq, PartialEq)]
-pub enum TrailingToken {
-    None,
-    Semi,
-    Gt,
-    /// If the trailing token is a comma, then capture it
-    /// Otherwise, ignore the trailing token
-    MaybeComma,
-}
-
 /// Like `maybe_whole_expr`, but for things other than expressions.
 #[macro_export]
 macro_rules! maybe_whole {
@@ -1509,7 +1499,7 @@ impl<'a> Parser<'a> {
         self.collect_tokens_trailing_token(
             AttrWrapper::empty(),
             ForceCollect::Yes,
-            |this, _attrs| Ok((f(this)?, TrailingToken::None)),
+            |this, _attrs| Ok((f(this)?, false)),
         )
     }
 

compiler/rustc_parse/src/parser/pat.rs

@@ -1,4 +1,4 @@
-use super::{ForceCollect, Parser, PathStyle, Restrictions, Trailing, TrailingToken};
+use super::{ForceCollect, Parser, PathStyle, Restrictions, Trailing};
 use crate::errors::{
     self, AmbiguousRangePattern, DotDotDotForRemainingFields, DotDotDotRangeToPatternNotAllowed,
     DotDotDotRestPattern, EnumPatternInsteadOfIdentifier, ExpectedBindingLeftOfAt,
@@ -1297,9 +1297,8 @@ impl<'a> Parser<'a> {
 
                     last_non_comma_dotdot_span = Some(this.prev_token.span);
 
-                    // We just ate a comma, so there's no need to use
-                    // `TrailingToken::Comma`
-                    Ok((field, TrailingToken::None))
+                    // We just ate a comma, so there's no need to capture a trailing token.
+                    Ok((field, false))
                 })?;
 
             fields.push(field)

compiler/rustc_parse/src/parser/stmt.rs

@@ -3,7 +3,6 @@ use super::diagnostics::AttemptLocalParseRecovery;
 use super::expr::LhsExpr;
 use super::pat::{PatternLocation, RecoverComma};
 use super::path::PathStyle;
-use super::TrailingToken;
 use super::{
     AttrWrapper, BlockMode, FnParseMode, ForceCollect, Parser, Restrictions, SemiColonMode,
 };
@@ -149,11 +148,7 @@ impl<'a> Parser<'a> {
 
             if this.eat(&token::Not) {
                 let stmt_mac = this.parse_stmt_mac(lo, attrs, path)?;
-                if this.token == token::Semi {
-                    return Ok((stmt_mac, TrailingToken::Semi));
-                } else {
-                    return Ok((stmt_mac, TrailingToken::None));
-                }
+                return Ok((stmt_mac, this.token == token::Semi));
             }
 
             let expr = if this.eat(&token::OpenDelim(Delimiter::Brace)) {
@@ -167,7 +162,7 @@ impl<'a> Parser<'a> {
                 this.parse_expr_dot_or_call_with(expr, lo, attrs)
             })?;
             // `DUMMY_SP` will get overwritten later in this function
-            Ok((this.mk_stmt(rustc_span::DUMMY_SP, StmtKind::Expr(expr)), TrailingToken::None))
+            Ok((this.mk_stmt(rustc_span::DUMMY_SP, StmtKind::Expr(expr)), false))
         })?;
 
         if let StmtKind::Expr(expr) = stmt.kind {
@@ -241,10 +236,7 @@ impl<'a> Parser<'a> {
             self.collect_tokens_trailing_token(attrs, ForceCollect::Yes, |this, attrs| {
                 let local = this.parse_local(attrs)?;
                 // FIXME - maybe capture semicolon in recovery?
-                Ok((
-                    this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Let(local)),
-                    TrailingToken::None,
-                ))
+                Ok((this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Let(local)), false))
             })?;
         self.dcx()
             .emit_err(errors::InvalidVariableDeclaration { span: lo, sub: subdiagnostic(lo) });
@@ -261,11 +253,7 @@ impl<'a> Parser<'a> {
         self.collect_tokens_trailing_token(attrs, force_collect, |this, attrs| {
             this.expect_keyword(kw::Let)?;
             let local = this.parse_local(attrs)?;
-            let trailing = if capture_semi && this.token.kind == token::Semi {
-                TrailingToken::Semi
-            } else {
-                TrailingToken::None
-            };
+            let trailing = capture_semi && this.token.kind == token::Semi;
             Ok((this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Let(local)), trailing))
         })
     }