Auto merge of #36969 - nnethercote:rename-Parser-fields, r=eddyb

Clarify the positions of the lexer and parser

The lexer and parser use unclear names to indicate their positions in the
source code. I propose the following renamings.

Lexer:
```
pos      -> next_pos      # it's actually the next pos!
last_pos -> pos           # it's actually the current pos!
curr     -> ch            # the current char
curr_is  -> ch_is         # tests the current char
col (unchanged)           # the current column
```
parser
```
- last_span       -> prev_span          # the previous token's span
- last_token_kind -> prev_token_kind    # the previous token's kind
- LastTokenKind   -> PrevTokenKind      # ditto (but the type)
- token (unchanged)                     # the current token
- span (unchanged)                      # the current span
```

Things to note:
- This proposal removes all uses of "last", which is an unclear word because it
  could mean (a) previous, (b) final, or (c) most recent, i.e. current.
- The "current" things (ch, col, token, span) consistently lack a prefix. The
  "previous" and "next" things consistently have a prefix.

1 files changed, 6 insertions, 6 deletions

diff --git a/src/libsyntax/parse/attr.rs b/src/libsyntax/parse/attr.rs
index 9eac024edb1..3cb34fa3c91 100644
--- a/src/libsyntax/parse/attr.rs
+++ b/src/libsyntax/parse/attr.rs
@@ -126,7 +126,7 @@ impl<'a> Parser<'a> {
                 self.expect(&token::OpenDelim(token::Bracket))?;
                 let meta_item = self.parse_meta_item()?;
                 self.expect(&token::CloseDelim(token::Bracket))?;
-                let hi = self.last_span.hi;
+                let hi = self.prev_span.hi;
 
                 (mk_sp(lo, hi), meta_item, style)
             }
@@ -231,16 +231,16 @@ impl<'a> Parser<'a> {
             token::Eq => {
                 self.bump();
                 let lit = self.parse_unsuffixed_lit()?;
-                let hi = self.last_span.hi;
+                let hi = self.prev_span.hi;
                 Ok(P(spanned(lo, hi, ast::MetaItemKind::NameValue(name, lit))))
             }
             token::OpenDelim(token::Paren) => {
                 let inner_items = self.parse_meta_seq()?;
-                let hi = self.last_span.hi;
+                let hi = self.prev_span.hi;
                 Ok(P(spanned(lo, hi, ast::MetaItemKind::List(name, inner_items))))
             }
             _ => {
-                let hi = self.last_span.hi;
+                let hi = self.prev_span.hi;
                 Ok(P(spanned(lo, hi, ast::MetaItemKind::Word(name))))
             }
         }
@@ -253,14 +253,14 @@ impl<'a> Parser<'a> {
 
         match self.parse_unsuffixed_lit() {
             Ok(lit) => {
-                return Ok(spanned(lo, self.last_span.hi, ast::NestedMetaItemKind::Literal(lit)))
+                return Ok(spanned(lo, self.prev_span.hi, ast::NestedMetaItemKind::Literal(lit)))
             }
             Err(ref mut err) => self.diagnostic().cancel(err)
         }
 
         match self.parse_meta_item() {
             Ok(mi) => {
-                return Ok(spanned(lo, self.last_span.hi, ast::NestedMetaItemKind::MetaItem(mi)))
+                return Ok(spanned(lo, self.prev_span.hi, ast::NestedMetaItemKind::MetaItem(mi)))
             }
             Err(ref mut err) => self.diagnostic().cancel(err)
         }