Convert a bool to Trailing.

This pre-existing type is suitable for use with the return value of the
`f` parameter in `collect_tokens_trailing_token`. The more descriptive
name will be useful because the next commit will add another boolean
value to the return value of `f`.

Author: nnethercote

compiler/rustc_parse/src/parser/attr.rs

@@ -8,7 +8,9 @@ use rustc_span::{sym, BytePos, Span};
 use thin_vec::ThinVec;
 use tracing::debug;
 
-use super::{AttrWrapper, Capturing, FnParseMode, ForceCollect, Parser, ParserRange, PathStyle};
+use super::{
+    AttrWrapper, Capturing, FnParseMode, ForceCollect, Parser, ParserRange, PathStyle, Trailing,
+};
 use crate::{errors, fluent_generated as fluent, maybe_whole};
 
 // Public for rustfmt usage
@@ -273,7 +275,7 @@ impl<'a> Parser<'a> {
             if is_unsafe {
                 this.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
             }
-            Ok((ast::AttrItem { unsafety, path, args, tokens: None }, false))
+            Ok((ast::AttrItem { unsafety, path, args, tokens: None }, Trailing::No))
         };
         // Attr items don't have attributes.
         self.collect_tokens_trailing_token(AttrWrapper::empty(), force_collect, do_parse)

compiler/rustc_parse/src/parser/attr_wrapper.rs

@@ -12,7 +12,7 @@ use rustc_span::{sym, Span, DUMMY_SP};
 
 use super::{
     Capturing, FlatToken, ForceCollect, NodeRange, NodeReplacement, Parser, ParserRange,
-    TokenCursor,
+    TokenCursor, Trailing,
 };
 
 /// A wrapper type to ensure that the parser handles outer attributes correctly.
@@ -168,7 +168,7 @@ impl ToAttrTokenStream for LazyAttrTokenStreamImpl {
 impl<'a> Parser<'a> {
     /// Parses code with `f`. If appropriate, it records the tokens (in
     /// `LazyAttrTokenStream` form) that were parsed in the result, accessible
-    /// via the `HasTokens` trait. The second (bool) part of the callback's
+    /// via the `HasTokens` trait. The `Trailing` part of the callback's
     /// result indicates if an extra token should be captured, e.g. a comma or
     /// semicolon.
     ///
@@ -201,7 +201,7 @@ impl<'a> Parser<'a> {
         &mut self,
         attrs: AttrWrapper,
         force_collect: ForceCollect,
-        f: impl FnOnce(&mut Self, ast::AttrVec) -> PResult<'a, (R, bool)>,
+        f: impl FnOnce(&mut Self, ast::AttrVec) -> PResult<'a, (R, Trailing)>,
     ) -> PResult<'a, R> {
         // We must collect if anything could observe the collected tokens, i.e.
         // if any of the following conditions hold.
@@ -234,9 +234,9 @@ impl<'a> Parser<'a> {
         // `Parser::parse_inner_attributes`.
         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);
+            let f_res = f(self, attrs.attrs);
             self.capture_state.capturing = prev_capturing;
-            ret_and_trailing?
+            f_res?
         };
 
         // When we're not in `capture_cfg` mode, then skip collecting and
@@ -282,7 +282,7 @@ impl<'a> Parser<'a> {
         let parser_replacements_end = self.capture_state.parser_replacements.len();
 
         assert!(
-            !(self.break_last_token && capture_trailing),
+            !(self.break_last_token && matches!(capture_trailing, Trailing::Yes)),
             "Cannot set break_last_token and have trailing token"
         );
 

compiler/rustc_parse/src/parser/expr.rs

@@ -2462,7 +2462,7 @@ impl<'a> Parser<'a> {
                     id: DUMMY_NODE_ID,
                     is_placeholder: false,
                 },
-                this.token == token::Comma,
+                Trailing::from(this.token == token::Comma),
             ))
         })
     }
@@ -3243,7 +3243,7 @@ impl<'a> Parser<'a> {
                     id: DUMMY_NODE_ID,
                     is_placeholder: false,
                 },
-                false,
+                Trailing::No,
             ))
         })
     }
@@ -3752,7 +3752,7 @@ impl<'a> Parser<'a> {
                     id: DUMMY_NODE_ID,
                     is_placeholder: false,
                 },
-                this.token == token::Comma,
+                Trailing::from(this.token == token::Comma),
             ))
         })
     }
@@ -3848,12 +3848,14 @@ 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 = (this.restrictions.contains(Restrictions::STMT_EXPR)
-                 && this.token == 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 == token::Comma;
+            let trailing = Trailing::from(
+                this.restrictions.contains(Restrictions::STMT_EXPR)
+                     && this.token == 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 == token::Comma,
+            );
             Ok((res, trailing))
         })
     }

compiler/rustc_parse/src/parser/generics.rs

@@ -7,7 +7,7 @@ use rustc_span::symbol::{kw, Ident};
 use rustc_span::Span;
 use thin_vec::ThinVec;
 
-use super::{ForceCollect, Parser};
+use super::{ForceCollect, Parser, Trailing};
 use crate::errors::{
     self, MultipleWhereClauses, UnexpectedDefaultValueForLifetimeInGenericParameters,
     UnexpectedSelfInGenericParameters, WhereClauseBeforeTupleStructBody,
@@ -228,13 +228,13 @@ impl<'a> Parser<'a> {
                                     span: where_predicate.span(),
                                 });
                                 // FIXME - try to continue parsing other generics?
-                                return Ok((None, false));
+                                return Ok((None, Trailing::No));
                             }
                             Err(err) => {
                                 err.cancel();
                                 // FIXME - maybe we should overwrite 'self' outside of `collect_tokens`?
                                 this.restore_snapshot(snapshot);
-                                return Ok((None, false));
+                                return Ok((None, Trailing::No));
                             }
                         }
                     } else {
@@ -248,14 +248,14 @@ impl<'a> Parser<'a> {
                                     .emit_err(errors::AttrWithoutGenerics { span: attrs[0].span });
                             }
                         }
-                        return Ok((None, false));
+                        return Ok((None, Trailing::No));
                     };
 
                     if !this.eat(&token::Comma) {
                         done = true;
                     }
                     // We just ate the comma, so no need to capture the trailing token.
-                    Ok((param, false))
+                    Ok((param, Trailing::No))
                 })?;
 
             if let Some(param) = param {

compiler/rustc_parse/src/parser/item.rs

@@ -145,7 +145,7 @@ impl<'a> Parser<'a> {
                 let span = lo.to(this.prev_token.span);
                 let id = DUMMY_NODE_ID;
                 let item = Item { ident, attrs, id, kind, vis, span, tokens: None };
-                return Ok((Some(item), false));
+                return Ok((Some(item), Trailing::No));
             }
 
             // At this point, we have failed to parse an item.
@@ -160,7 +160,7 @@ impl<'a> Parser<'a> {
             if !attrs_allowed {
                 this.recover_attrs_no_item(&attrs)?;
             }
-            Ok((None, false))
+            Ok((None, Trailing::No))
         })
     }
 
@@ -1554,7 +1554,7 @@ impl<'a> Parser<'a> {
 
                 let vis = this.parse_visibility(FollowedByType::No)?;
                 if !this.recover_nested_adt_item(kw::Enum)? {
-                    return Ok((None, false));
+                    return Ok((None, Trailing::No));
                 }
                 let ident = this.parse_field_ident("enum", vlo)?;
 
@@ -1566,7 +1566,7 @@ impl<'a> Parser<'a> {
                     this.bump();
                     this.parse_delim_args()?;
 
-                    return Ok((None, this.token == token::Comma));
+                    return Ok((None, Trailing::from(this.token == token::Comma)));
                 }
 
                 let struct_def = if this.check(&token::OpenDelim(Delimiter::Brace)) {
@@ -1623,7 +1623,7 @@ impl<'a> Parser<'a> {
                     is_placeholder: false,
                 };
 
-                Ok((Some(vr), this.token == token::Comma))
+                Ok((Some(vr), Trailing::from(this.token == token::Comma)))
             },
         )
         .map_err(|mut err| {
@@ -1815,7 +1815,7 @@ impl<'a> Parser<'a> {
                         attrs,
                         is_placeholder: false,
                     },
-                    p.token == token::Comma,
+                    Trailing::from(p.token == token::Comma),
                 ))
             })
         })
@@ -1830,7 +1830,8 @@ 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, false))
+            this.parse_single_struct_field(adt_ty, lo, vis, attrs)
+                .map(|field| (field, Trailing::No))
         })
     }
 
@@ -2810,7 +2811,7 @@ 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?, false));
+                return Ok((res?, Trailing::No));
             }
 
             let is_name_required = match this.token.kind {
@@ -2826,7 +2827,7 @@ 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), false))
+                        Ok((dummy_arg(ident, guar), Trailing::No))
                     } else {
                         Err(err)
                     };
@@ -2869,7 +2870,7 @@ impl<'a> Parser<'a> {
 
             Ok((
                 Param { attrs, id: ast::DUMMY_NODE_ID, is_placeholder: false, pat, span, ty },
-                false,
+                Trailing::No,
             ))
         })
     }

compiler/rustc_parse/src/parser/mod.rs

@@ -388,6 +388,12 @@ enum Trailing {
     Yes,
 }
 
+impl From<bool> for Trailing {
+    fn from(b: bool) -> Trailing {
+        if b { Trailing::Yes } else { Trailing::No }
+    }
+}
+
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub(super) enum TokenDescription {
     ReservedIdentifier,
@@ -1549,7 +1555,7 @@ impl<'a> Parser<'a> {
         self.collect_tokens_trailing_token(
             AttrWrapper::empty(),
             ForceCollect::Yes,
-            |this, _attrs| Ok((f(this)?, false)),
+            |this, _attrs| Ok((f(this)?, Trailing::No)),
         )
     }
 

compiler/rustc_parse/src/parser/pat.rs

@@ -1318,7 +1318,7 @@ 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 capture a trailing token.
-                    Ok((field, false))
+                    Ok((field, Trailing::No))
                 })?;
 
             fields.push(field)

compiler/rustc_parse/src/parser/stmt.rs

@@ -21,6 +21,7 @@ use super::pat::{PatternLocation, RecoverComma};
 use super::path::PathStyle;
 use super::{
     AttrWrapper, BlockMode, FnParseMode, ForceCollect, Parser, Restrictions, SemiColonMode,
+    Trailing,
 };
 use crate::errors::MalformedLoopLabel;
 use crate::{errors, maybe_whole};
@@ -68,7 +69,7 @@ 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 = capture_semi && this.token == token::Semi;
+                let trailing = Trailing::from(capture_semi && this.token == token::Semi);
                 Ok((this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Let(local)), trailing))
             })?
         } else if self.is_kw_followed_by_ident(kw::Mut) && self.may_recover() {
@@ -106,7 +107,7 @@ impl<'a> Parser<'a> {
             let stmt = self.collect_tokens_trailing_token(
                 AttrWrapper::empty(),
                 force_collect,
-                |this, _empty_attrs| Ok((this.parse_stmt_path_start(lo, attrs)?, false)),
+                |this, _empty_attrs| Ok((this.parse_stmt_path_start(lo, attrs)?, Trailing::No)),
             );
             match stmt {
                 Ok(stmt) => stmt,
@@ -133,7 +134,7 @@ impl<'a> Parser<'a> {
                 AttrWrapper::empty(),
                 force_collect,
                 |this, _empty_attrs| {
-                    Ok((this.parse_expr_res(Restrictions::STMT_EXPR, attrs)?, false))
+                    Ok((this.parse_expr_res(Restrictions::STMT_EXPR, attrs)?, Trailing::No))
                 },
             )?;
             if matches!(e.kind, ExprKind::Assign(..)) && self.eat_keyword(kw::Else) {
@@ -155,7 +156,7 @@ impl<'a> Parser<'a> {
 
             if this.eat(&token::Not) {
                 let stmt_mac = this.parse_stmt_mac(lo, attrs, path)?;
-                return Ok((stmt_mac, this.token == token::Semi));
+                return Ok((stmt_mac, Trailing::from(this.token == token::Semi)));
             }
 
             let expr = if this.eat(&token::OpenDelim(Delimiter::Brace)) {
@@ -169,7 +170,7 @@ impl<'a> Parser<'a> {
                 this.parse_expr_dot_or_call_with(attrs, expr, lo)
             })?;
             // `DUMMY_SP` will get overwritten later in this function
-            Ok((this.mk_stmt(rustc_span::DUMMY_SP, StmtKind::Expr(expr)), false))
+            Ok((this.mk_stmt(rustc_span::DUMMY_SP, StmtKind::Expr(expr)), Trailing::No))
         })?;
 
         if let StmtKind::Expr(expr) = stmt.kind {
@@ -242,7 +243,7 @@ impl<'a> Parser<'a> {
         let stmt = self.collect_tokens_trailing_token(attrs, force_collect, |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)), false))
+            Ok((this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Let(local)), Trailing::No))
         })?;
         self.dcx()
             .emit_err(errors::InvalidVariableDeclaration { span: lo, sub: subdiagnostic(lo) });