Auto merge of #45773 - Badel2:dotdoteq, r=petrochenkov

Add error for `...` in expressions

Follow-up to https://github.com/rust-lang/rust/pull/44709
Tracking issue: https://github.com/rust-lang/rust/issues/28237

* Using `...` in expressions was a warning, now it's an error
* The error message suggests using `..` or `..=` instead, and explains the difference
* Updated remaining occurrences of `...` to `..=`

r? petrochenkov

src/libcore/slice/mod.rs

@@ -16,9 +16,6 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
-// FIXME: after next stage0, change RangeInclusive { ... } back to ..=
-use ops::RangeInclusive;
-
 // How this module is organized.
 //
 // The library infrastructure for slices is fairly messy. There's
@@ -1047,32 +1044,32 @@ impl<T> SliceIndex<[T]> for ops::RangeToInclusive<usize> {
 
     #[inline]
     fn get(self, slice: &[T]) -> Option<&[T]> {
-        (RangeInclusive { start: 0, end: self.end }).get(slice)
+        (0..=self.end).get(slice)
     }
 
     #[inline]
     fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
-        (RangeInclusive { start: 0, end: self.end }).get_mut(slice)
+        (0..=self.end).get_mut(slice)
     }
 
     #[inline]
     unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
-        (RangeInclusive { start: 0, end: self.end }).get_unchecked(slice)
+        (0..=self.end).get_unchecked(slice)
     }
 
     #[inline]
     unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
-        (RangeInclusive { start: 0, end: self.end }).get_unchecked_mut(slice)
+        (0..=self.end).get_unchecked_mut(slice)
     }
 
     #[inline]
     fn index(self, slice: &[T]) -> &[T] {
-        (RangeInclusive { start: 0, end: self.end }).index(slice)
+        (0..=self.end).index(slice)
     }
 
     #[inline]
     fn index_mut(self, slice: &mut [T]) -> &mut [T] {
-        (RangeInclusive { start: 0, end: self.end }).index_mut(slice)
+        (0..=self.end).index_mut(slice)
     }
 }
 

src/librustc/ty/maps/on_disk_cache.rs

@@ -165,7 +165,7 @@ impl<'a> CacheDecoder<'a> {
     fn find_filemap_prev_bytepos(&self,
                                  prev_bytepos: BytePos)
                                  -> Option<(BytePos, StableFilemapId)> {
-        for (start, id) in self.prev_filemap_starts.range(BytePos(0) ... prev_bytepos).rev() {
+        for (start, id) in self.prev_filemap_starts.range(BytePos(0) ..= prev_bytepos).rev() {
             return Some((*start, *id))
         }
 

src/libsyntax/parse/parser.rs

@@ -2783,10 +2783,11 @@ impl<'a> Parser<'a> {
             if op.precedence() < min_prec {
                 break;
             }
-            // Warn about deprecated ... syntax (until SNAP)
+            // Check for deprecated `...` syntax
-            if self.token == token::DotDotDot {
+            if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
-                self.warn_dotdoteq(self.span);
+                self.err_dotdotdot_syntax(self.span);
             }
+
             self.bump();
             if op.is_comparison() {
                 self.check_no_chained_comparison(&lhs, &op);
@@ -2819,7 +2820,6 @@ impl<'a> Parser<'a> {
                 //
                 // We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other
                 // two variants are handled with `parse_prefix_range_expr` call above.
-                // (and `x...y`/`x...` until SNAP)
                 let rhs = if self.is_at_start_of_range_notation_rhs() {
                     Some(self.parse_assoc_expr_with(op.precedence() + 1,
                                                     LhsExpr::NotYetParsed)?)
@@ -3007,22 +3007,22 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr` (and `...expr` until SNAP)
+    /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
     fn parse_prefix_range_expr(&mut self,
                                already_parsed_attrs: Option<ThinVec<Attribute>>)
                                -> PResult<'a, P<Expr>> {
-        // SNAP remove DotDotDot
+        // Check for deprecated `...` syntax
+        if self.token == token::DotDotDot {
+            self.err_dotdotdot_syntax(self.span);
+        }
+
         debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token),
-                      "parse_prefix_range_expr: token {:?} is not DotDot/DotDotDot/DotDotEq",
+                      "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
                       self.token);
         let tok = self.token.clone();
         let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
         let lo = self.span;
         let mut hi = self.span;
-        // Warn about deprecated ... syntax (until SNAP)
-        if tok == token::DotDotDot {
-            self.warn_dotdoteq(self.span);
-        }
         self.bump();
         let opt_end = if self.is_at_start_of_range_notation_rhs() {
             // RHS must be parsed with more associativity than the dots.
@@ -4332,9 +4332,13 @@ impl<'a> Parser<'a> {
         }).emit();
     }
 
-    fn warn_dotdoteq(&self, span: Span) {
+    fn err_dotdotdot_syntax(&self, span: Span) {
-        self.diagnostic().struct_span_warn(span, {
+        self.diagnostic().struct_span_err(span, {
-            "`...` is being replaced by `..=`"
+            "`...` syntax cannot be used in expressions"
+        }).help({
+            "Use `..` if you need an exclusive range (a < b)"
+        }).help({
+            "or `..=` if you need an inclusive range (a <= b)"
         }).emit();
     }
 

src/libsyntax/parse/token.rs

@@ -222,8 +222,8 @@ impl Token {
             BinOp(Or) | OrOr                  | // closure
             BinOp(And)                        | // reference
             AndAnd                            | // double reference
+            // DotDotDot is no longer supported, but we need some way to display the error
             DotDot | DotDotDot | DotDotEq     | // range notation
-                // SNAP remove DotDotDot
             Lt | BinOp(Shl)                   | // associated path
             ModSep                            | // global path
             Pound                             => true, // expression attributes

src/libsyntax/print/pprust.rs

@@ -2213,7 +2213,7 @@ impl<'a> State<'a> {
                 if limits == ast::RangeLimits::HalfOpen {
                     self.s.word("..")?;
                 } else {
-                    self.s.word("...")?;
+                    self.s.word("..=")?;
                 }
                 if let Some(ref e) = *end {
                     self.print_expr_maybe_paren(e, fake_prec)?;

src/libsyntax/util/parser.rs

@@ -106,7 +106,8 @@ impl AssocOp {
             Token::OrOr => Some(LOr),
             Token::DotDot => Some(DotDot),
             Token::DotDotEq => Some(DotDotEq),
-            Token::DotDotDot => Some(DotDotEq), // remove this after SNAP
+            // DotDotDot is no longer supported, but we need some way to display the error
+            Token::DotDotDot => Some(DotDotEq),
             Token::Colon => Some(Colon),
             _ if t.is_keyword(keywords::As) => Some(As),
             _ => None

src/test/parse-fail/range_inclusive_dotdotdot.rs

@@ -0,0 +1,38 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// compile-flags: -Z parse-only -Z continue-parse-after-error
+
+// Make sure that inclusive ranges with `...` syntax don't parse.
+
+#![feature(inclusive_range_syntax, inclusive_range)]
+
+use std::ops::RangeToInclusive;
+
+fn return_range_to() -> RangeToInclusive<i32> {
+    return ...1; //~ERROR `...` syntax cannot be used in expressions
+                 //~^HELP  Use `..` if you need an exclusive range (a < b)
+                 //~^^HELP or `..=` if you need an inclusive range (a <= b)
+}
+
+pub fn main() {
+    let x = ...0;    //~ERROR `...` syntax cannot be used in expressions
+                     //~^HELP  Use `..` if you need an exclusive range (a < b)
+                     //~^^HELP or `..=` if you need an inclusive range (a <= b)
+
+    let x = 5...5;   //~ERROR `...` syntax cannot be used in expressions
+                     //~^HELP  Use `..` if you need an exclusive range (a < b)
+                     //~^^HELP or `..=` if you need an inclusive range (a <= b)
+
+    for _ in 0...1 {} //~ERROR `...` syntax cannot be used in expressions
+                     //~^HELP  Use `..` if you need an exclusive range (a < b)
+                     //~^^HELP or `..=` if you need an inclusive range (a <= b)
+}
+

src/test/run-pass-fulldeps/issue-35829.rs

@@ -41,8 +41,8 @@ fn main() {
     let raw_byte_string_lit_kind = LitKind::ByteStr(Rc::new(b"#\"two\"#".to_vec()));
     assert_eq!(raw_byte_string.node, ExprKind::Lit(P(dummy_spanned(raw_byte_string_lit_kind))));
 
-    // check dotdotdot
+    // check dotdoteq
-    let closed_range = quote_expr!(&cx, 0 ... 1);
+    let closed_range = quote_expr!(&cx, 0 ..= 1);
     assert_eq!(closed_range.node, ExprKind::Range(
         Some(quote_expr!(&cx, 0)),
         Some(quote_expr!(&cx, 1)),