Make the parser’s ‘expected <foo>, found <bar>’ errors more accurate

As an example of what this changes, the following code:

    let x: [int ..4];

Currently spits out ‘expected `]`, found `..`’. However, a comma would also be
valid there, as would a number of other tokens. This change adjusts the parser
to produce more accurate errors, so that that example now produces ‘expected one
of `(`, `+`, `,`, `::`, or `]`, found `..`’.

Author: ftxqxd

src/libsyntax/parse/parser.rs

@@ -0,0 +1,13 @@
+// Copyright 2014 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.
+
+fn main() {
+    let x: [int ..3]; //~ ERROR expected one of `(`, `+`, `,`, `::`, or `]`, found `..`
+}

src/test/compile-fail/better-expected.rs

@@ -8,4 +8,4 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-# //~ ERROR 11:1: 11:2 error: expected `[`, found `<eof>`
+# //~ ERROR 11:1: 11:2 error: expected one of `!` or `[`, found `<eof>`

src/test/compile-fail/column-offset-1-based.rs

@@ -8,4 +8,4 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-impl Foo; //~ ERROR expected `{`, found `;`
+impl Foo; //~ ERROR expected one of `(`, `+`, `::`, or `{`, found `;`

src/test/compile-fail/empty-impl-semicolon.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern:expected `[`, found `vec`
+// error-pattern:expected one of `!` or `[`, found `vec`
 mod blade_runner {
     #vec[doc(
         brief = "Blade Runner is probably the best movie ever",

src/test/compile-fail/issue-1655.rs

@@ -12,5 +12,5 @@
 
 fn main() {
     let t = (42i, 42i);
-    t.0::<int>; //~ ERROR expected one of `;`, `}`, found `::`
+    t.0::<int>; //~ ERROR expected one of `.`, `;`, `}`, or an operator, found `::`
 }

src/test/compile-fail/issue-19096.rs

@@ -13,4 +13,4 @@
 fn main()
 {
     let x = 3
-} //~ ERROR: expected `;`, found `}`
+} //~ ERROR: expected one of `.`, `;`, or an operator, found `}`

src/test/compile-fail/issue-3036.rs

@@ -11,7 +11,7 @@
 fn main() {
     let a = Vec::new();
     match a {
-        [1, tail.., tail..] => {}, //~ ERROR: expected `,`, found `..`
+        [1, tail.., tail..] => {}, //~ ERROR: expected one of `!`, `,`, or `@`, found `..`
         _ => ()
     }
 }

src/test/compile-fail/match-vec-invalid.rs

@@ -12,7 +12,7 @@ struct S {
  y: int
 }
 
-impl Cmp, ToString for S { //~ ERROR: expected `{`, found `,`
+impl Cmp, ToString for S { //~ ERROR: expected one of `(`, `+`, `::`, or `{`, found `,`
   fn eq(&&other: S) { false }
   fn to_string(&self) -> String { "hi".to_string() }
 }

src/test/compile-fail/multitrait.rs

@@ -12,5 +12,5 @@
 
 pub fn main() {
     struct Foo { x: int }
-    let mut Foo { x: x } = Foo { x: 3 }; //~ ERROR: expected `;`, found `{`
+    let mut Foo { x: x } = Foo { x: 3 }; //~ ERROR: expected one of `:`, `;`, `=`, or `@`, found `{`
 }

src/test/compile-fail/mut-patterns.rs

@@ -8,5 +8,5 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-fn foo(x) { //~ ERROR expected `:`, found `)`
+fn foo(x) { //~ ERROR expected one of `!`, `:`, or `@`, found `)`
 }

src/test/compile-fail/omitted-arg-in-item-fn.rs

@@ -10,7 +10,7 @@
 
 pub fn main() {
     match 22i {
-        0 .. 3 => {} //~ ERROR expected `=>`, found `..`
+        0 .. 3 => {} //~ ERROR expected one of `...`, `=>`, or `|`, found `..`
         _ => {}
     }
 }

src/test/compile-fail/pat-range-bad-dots.rs

@@ -10,5 +10,5 @@
 
 static s: &'static str =
     r#"
-      "## //~ ERROR expected `;`, found `#`
+      "## //~ ERROR expected one of `.`, `;`, or an operator, found `#`
 ;

src/test/compile-fail/raw-str-unbalanced.rs

@@ -8,4 +8,4 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-type closure = Box<lt/fn()>; //~ ERROR expected `,`, found `/`
+type closure = Box<lt/fn()>; //~ ERROR expected one of `(`, `+`, `,`, `::`, or `>`, found `/`

src/test/compile-fail/removed-syntax-closure-lifetime.rs

@@ -8,4 +8,4 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-enum e = int; //~ ERROR expected `{`, found `=`
+enum e = int; //~ ERROR expected one of `<` or `{`, found `=`

src/test/compile-fail/removed-syntax-enum-newtype.rs

@@ -8,4 +8,4 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-type v = [int * 3]; //~ ERROR expected `]`, found `*`
+type v = [int * 3]; //~ ERROR expected one of `(`, `+`, `,`, `::`, or `]`, found `*`

src/test/compile-fail/removed-syntax-fixed-vec.rs

@@ -11,5 +11,5 @@
 fn removed_moves() {
     let mut x = 0;
     let y <- x;
-    //~^ ERROR expected `;`, found `<-`
+    //~^ ERROR expected one of `!`, `:`, `;`, `=`, or `@`, found `<-`
 }

src/test/compile-fail/removed-syntax-larrow-init.rs

@@ -12,5 +12,5 @@ fn removed_moves() {
     let mut x = 0;
     let y = 0;
     y <- x;
-    //~^ ERROR expected one of `;`, `}`, found `<-`
+    //~^ ERROR expected one of `!`, `.`, `::`, `;`, `{`, `}`, or an operator, found `<-`
 }

src/test/compile-fail/removed-syntax-larrow-move.rs

@@ -11,5 +11,5 @@
 fn f() {
     let v = [mut 1, 2, 3, 4];
     //~^  ERROR expected identifier, found keyword `mut`
-    //~^^ ERROR expected `]`, found `1`
+    //~^^ ERROR expected one of `!`, `,`, `.`, `::`, `]`, `{`, or an operator, found `1`
 }

src/test/compile-fail/removed-syntax-mut-vec-expr.rs

@@ -10,4 +10,4 @@
 
 type v = [mut int];
     //~^  ERROR expected identifier, found keyword `mut`
-    //~^^ ERROR expected `]`, found `int`
+    //~^^ ERROR expected one of `(`, `+`, `,`, `::`, or `]`, found `int`

src/test/compile-fail/removed-syntax-mut-vec-ty.rs

@@ -8,4 +8,4 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-type bptr = &lifetime/int; //~ ERROR expected `;`, found `/`
+type bptr = &lifetime/int; //~ ERROR expected one of `(`, `+`, `::`, or `;`, found `/`

src/test/compile-fail/removed-syntax-ptr-lifetime.rs

@@ -8,4 +8,4 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-type t = { f: () }; //~ ERROR expected type, found token OpenDelim(Brace)
+type t = { f: () }; //~ ERROR expected type, found `{`

src/test/compile-fail/removed-syntax-record.rs

@@ -11,5 +11,5 @@
 fn f() {
     let a_box = box mut 42;
     //~^  ERROR expected identifier, found keyword `mut`
-    //~^^ ERROR expected `;`, found `42`
+    //~^^ ERROR expected one of `!`, `.`, `::`, `;`, `{`, or an operator, found `42`
 }

src/test/compile-fail/removed-syntax-uniq-mut-expr.rs

@@ -10,4 +10,4 @@
 
 type mut_box = Box<mut int>;
     //~^  ERROR expected identifier, found keyword `mut`
-    //~^^ ERROR expected `,`, found `int`
+    //~^^ ERROR expected one of `(`, `+`, `,`, `::`, or `>`, found `int`

src/test/compile-fail/removed-syntax-uniq-mut-ty.rs

@@ -16,5 +16,5 @@ fn removed_with() {
 
     let a = S { foo: (), bar: () };
     let b = S { foo: () with a };
-    //~^ ERROR expected one of `,`, `}`, found `with`
+    //~^ ERROR expected one of `,`, `.`, `}`, or an operator, found `with`
 }

src/test/compile-fail/removed-syntax-with-1.rs

@@ -20,7 +20,7 @@ impl Foo {
 
 fn main() {
     for x in Foo {
-        x: 3    //~ ERROR expected one of `;`, `}`
+        x: 3    //~ ERROR expected one of `!`, `.`, `::`, `;`, `{`, `}`, or an operator, found `:`
     }.hi() {
         println!("yo");
     }

src/test/compile-fail/struct-literal-in-for.rs

@@ -20,7 +20,7 @@ impl Foo {
 
 fn main() {
     if Foo {
-        x: 3    //~ ERROR expected one of `;`, `}`
+        x: 3    //~ ERROR expected one of `!`, `.`, `::`, `;`, `{`, `}`, or an operator, found `:`
     }.hi() {
         println!("yo");
     }

src/test/compile-fail/struct-literal-in-if.rs

@@ -14,7 +14,7 @@ struct Foo {
 
 fn main() {
     match Foo {
-        x: 3    //~ ERROR expected `=>`
+        x: 3    //~ ERROR expected one of `!`, `=>`, `@`, or `|`, found `:`
     } {
         Foo {
             x: x

src/test/compile-fail/struct-literal-in-match-discriminant.rs

@@ -20,7 +20,7 @@ impl Foo {
 
 fn main() {
     while Foo {
-        x: 3    //~ ERROR expected one of `;`, `}`
+        x: 3    //~ ERROR expected one of `!`, `.`, `::`, `;`, `{`, `}`, or an operator, found `:`
     }.hi() {
         println!("yo");
     }