Tweak chained comparison errors.

Lower case and give a more precise span: from operator to operator, not just the last one.

Author: huonw

src/libsyntax/parse/parser.rs

@@ -2882,12 +2882,13 @@ impl<'a> Parser<'a> {
  debug_assert!(ast_util::is_comparison_binop(outer_op));
  match lhs.node {
  ExprBinary(op, _, _) if ast_util::is_comparison_binop(op.node) => {
- let op_span = self.span;
+ // respan to include both operators
+ let op_span = mk_sp(op.span.lo, self.span.hi);
  self.span_err(op_span,
- "Chained comparison operators require parentheses");
+ "chained comparison operators require parentheses");
  if op.node == BiLt && outer_op == BiGt {
  self.span_help(op_span,
- "use ::< instead of < if you meant to specify type arguments");
+ "use `::<...>` instead of `<...>` if you meant to specify type arguments");
  }
  }
  _ => {}

src/test/compile-fail/require-parens-for-chained-comparison.rs

@@ -12,12 +12,12 @@ fn f<T>() {}
 
 fn main() {
  false == false == false;
- //~^ ERROR: Chained comparison operators require parentheses
+ //~^ ERROR: chained comparison operators require parentheses
 
  false == 0 < 2;
- //~^ ERROR: Chained comparison operators require parentheses
+ //~^ ERROR: chained comparison operators require parentheses
 
  f<X>();
- //~^ ERROR: Chained comparison operators require parentheses
- //~^^ HELP: use ::< instead of < if you meant to specify type arguments
+ //~^ ERROR: chained comparison operators require parentheses
+ //~^^ HELP: use `::<...>` instead of `<...>`
 }

src/test/compile-fail/unsized2.rs

@@ -15,6 +15,6 @@ fn f<X>() {}
 pub fn main() {
  f<type>();
  //~^ ERROR expected identifier, found keyword `type`
- //~^^ ERROR: Chained comparison operators require parentheses
- //~^^^ HELP: use ::< instead of < if you meant to specify type arguments
+ //~^^ ERROR: chained comparison
+ //~^^^ HELP: use `::<
 }