review comments: move back some methods and clean up wording

Author: estebank

src/libsyntax/parse/diagnostics.rs

@@ -5,18 +5,15 @@ use crate::ast::{
 };
 use crate::parse::{SeqSep, token, PResult, Parser};
 use crate::parse::parser::{BlockMode, PathStyle, SemiColonMode, TokenType, TokenExpectType};
-use crate::parse::token;
 use crate::print::pprust;
 use crate::ptr::P;
 use crate::source_map::Spanned;
 use crate::symbol::kw;
 use crate::ThinVec;
-use crate::tokenstream::TokenTree;
 use crate::util::parser::AssocOp;
-use errors::{Applicability, DiagnosticBuilder, DiagnosticId, FatalError};
+use errors::{Applicability, DiagnosticBuilder, DiagnosticId};
 use syntax_pos::{Span, DUMMY_SP, MultiSpan};
 use log::{debug, trace};
-use std::slice;
 
 pub enum Error {
     FileNotFoundForModule {
@@ -148,36 +145,8 @@ impl RecoverQPath for Expr {
 }
 
 impl<'a> Parser<'a> {
-    pub fn look_ahead<R, F>(&self, dist: usize, f: F) -> R where
-        F: FnOnce(&token::Token) -> R,
-    {
-        if dist == 0 {
-            return f(&self.token)
-        }
-
-        f(&match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
-            Some(tree) => match tree {
-                TokenTree::Token(_, tok) => tok,
-                TokenTree::Delimited(_, delim, _) => token::OpenDelim(delim),
-            },
-            None => token::CloseDelim(self.token_cursor.frame.delim),
-        })
-    }
-
-    crate fn look_ahead_span(&self, dist: usize) -> Span {
-        if dist == 0 {
-            return self.span
-        }
-
-        match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
-            Some(TokenTree::Token(span, _)) => span,
-            Some(TokenTree::Delimited(span, ..)) => span.entire(),
-            None => self.look_ahead_span(dist - 1),
-        }
-    }
-
     pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
-        self.sess.span_diagnostic.struct_span_fatal(self.span, m)
+        self.span_fatal(self.span, m)
     }
 
     pub fn span_fatal<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
@@ -243,6 +212,145 @@ impl<'a> Parser<'a> {
         err
     }
 
+    pub fn expected_one_of_not_found(
+        &mut self,
+        edible: &[token::Token],
+        inedible: &[token::Token],
+    ) -> PResult<'a, bool /* recovered */> {
+        fn tokens_to_string(tokens: &[TokenType]) -> String {
+            let mut i = tokens.iter();
+            // This might be a sign we need a connect method on Iterator.
+            let b = i.next()
+                     .map_or(String::new(), |t| t.to_string());
+            i.enumerate().fold(b, |mut b, (i, a)| {
+                if tokens.len() > 2 && i == tokens.len() - 2 {
+                    b.push_str(", or ");
+                } else if tokens.len() == 2 && i == tokens.len() - 2 {
+                    b.push_str(" or ");
+                } else {
+                    b.push_str(", ");
+                }
+                b.push_str(&a.to_string());
+                b
+            })
+        }
+
+        let mut expected = edible.iter()
+            .map(|x| TokenType::Token(x.clone()))
+            .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
+            .chain(self.expected_tokens.iter().cloned())
+            .collect::<Vec<_>>();
+        expected.sort_by_cached_key(|x| x.to_string());
+        expected.dedup();
+        let expect = tokens_to_string(&expected[..]);
+        let actual = self.this_token_to_string();
+        let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
+            let short_expect = if expected.len() > 6 {
+                format!("{} possible tokens", expected.len())
+            } else {
+                expect.clone()
+            };
+            (format!("expected one of {}, found `{}`", expect, actual),
+                (self.sess.source_map().next_point(self.prev_span),
+                format!("expected one of {} here", short_expect)))
+        } else if expected.is_empty() {
+            (format!("unexpected token: `{}`", actual),
+                (self.prev_span, "unexpected token after this".to_string()))
+        } else {
+            (format!("expected {}, found `{}`", expect, actual),
+                (self.sess.source_map().next_point(self.prev_span),
+                format!("expected {} here", expect)))
+        };
+        self.last_unexpected_token_span = Some(self.span);
+        let mut err = self.fatal(&msg_exp);
+        if self.token.is_ident_named("and") {
+            err.span_suggestion_short(
+                self.span,
+                "use `&&` instead of `and` for the boolean operator",
+                "&&".to_string(),
+                Applicability::MaybeIncorrect,
+            );
+        }
+        if self.token.is_ident_named("or") {
+            err.span_suggestion_short(
+                self.span,
+                "use `||` instead of `or` for the boolean operator",
+                "||".to_string(),
+                Applicability::MaybeIncorrect,
+            );
+        }
+        let sp = if self.token == token::Token::Eof {
+            // This is EOF, don't want to point at the following char, but rather the last token
+            self.prev_span
+        } else {
+            label_sp
+        };
+        match self.recover_closing_delimiter(&expected.iter().filter_map(|tt| match tt {
+            TokenType::Token(t) => Some(t.clone()),
+            _ => None,
+        }).collect::<Vec<_>>(), err) {
+            Err(e) => err = e,
+            Ok(recovered) => {
+                return Ok(recovered);
+            }
+        }
+
+        let is_semi_suggestable = expected.iter().any(|t| match t {
+            TokenType::Token(token::Semi) => true, // we expect a `;` here
+            _ => false,
+        }) && ( // a `;` would be expected before the current keyword
+            self.token.is_keyword(kw::Break) ||
+            self.token.is_keyword(kw::Continue) ||
+            self.token.is_keyword(kw::For) ||
+            self.token.is_keyword(kw::If) ||
+            self.token.is_keyword(kw::Let) ||
+            self.token.is_keyword(kw::Loop) ||
+            self.token.is_keyword(kw::Match) ||
+            self.token.is_keyword(kw::Return) ||
+            self.token.is_keyword(kw::While)
+        );
+        let cm = self.sess.source_map();
+        match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
+            (Ok(ref a), Ok(ref b)) if a.line != b.line && is_semi_suggestable => {
+                // The spans are in different lines, expected `;` and found `let` or `return`.
+                // High likelihood that it is only a missing `;`.
+                err.span_suggestion_short(
+                    label_sp,
+                    "a semicolon may be missing here",
+                    ";".to_string(),
+                    Applicability::MaybeIncorrect,
+                );
+                err.emit();
+                return Ok(true);
+            }
+            (Ok(ref a), Ok(ref b)) if a.line == b.line => {
+                // When the spans are in the same line, it means that the only content between
+                // them is whitespace, point at the found token in that case:
+                //
+                // X |     () => { syntax error };
+                //   |                    ^^^^^ expected one of 8 possible tokens here
+                //
+                // instead of having:
+                //
+                // X |     () => { syntax error };
+                //   |                   -^^^^^ unexpected token
+                //   |                   |
+                //   |                   expected one of 8 possible tokens here
+                err.span_label(self.span, label_exp);
+            }
+            _ if self.prev_span == syntax_pos::DUMMY_SP => {
+                // Account for macro context where the previous span might not be
+                // available to avoid incorrect output (#54841).
+                err.span_label(self.span, "unexpected token");
+            }
+            _ => {
+                err.span_label(sp, label_exp);
+                err.span_label(self.span, "unexpected token");
+            }
+        }
+        Err(err)
+    }
+
     /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
     /// passes through any errors encountered. Used for error recovery.
     crate fn eat_to_tokens(&mut self, kets: &[&token::Token]) {
@@ -939,9 +1047,6 @@ impl<'a> Parser<'a> {
                 String::new(),
                 Applicability::MachineApplicable,
             );
-            err.note("if you meant to use emplacement syntax, it is obsolete (for now, anyway)");
-            err.note("for more information on the status of emplacement syntax, see <\
-                      https://github.com/rust-lang/rust/issues/27779#issuecomment-378416911>");
             err.emit();
         }
     }
@@ -1050,12 +1155,12 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, ast::Arg> {
         let sp = arg.pat.span;
         arg.ty.node = TyKind::Err;
-        let mut err = self.struct_span_err(sp, "unexpected `self` argument in function");
+        let mut err = self.struct_span_err(sp, "unexpected `self` parameter in function");
         if is_trait_item {
-            err.span_label(sp, "must be the first associated function argument");
+            err.span_label(sp, "must be the first associated function parameter");
         } else {
-            err.span_label(sp, "not valid as function argument");
-            err.note("`self` is only valid as the first argument of an associated function");
+            err.span_label(sp, "not valid as function parameter");
+            err.note("`self` is only valid as the first parameter of an associated function");
         }
         err.emit();
         Ok(arg)