Range expressions

^Syntax
RangeExpression :
RangeExpr
| RangeFromExpr
| RangeToExpr
| RangeFullExpr

RangeExpr :
Expression .. Expression

RangeFromExpr :
Expression ..

RangeToExpr :
.. Expression

RangeFullExpr :
..

The .. operator will construct an object of one of the std::ops::Range (or core::ops::Range) variants, according to the following table:

Production	Syntax	Type	Range
RangeExpr	start..end	std::ops::Range	start ≤ x < end
RangeFromExpr	start..	std::ops::RangeFrom	start ≤ x
RangeToExpr	..end	std::ops::RangeTo	x < end
RangeFullExpr	..	std::ops::RangeFull	-

Examples:

# #![allow(unused_variables)]
#fn main() {
1..2;   // std::ops::Range
3..;    // std::ops::RangeFrom
..4;    // std::ops::RangeTo
..;     // std::ops::RangeFull
#}

The following expressions are equivalent.

# #![allow(unused_variables)]
#fn main() {
let x = std::ops::Range {start: 0, end: 10};
let y = 0..10;

assert_eq!(x, y);
#}

Ranges can be used in for loops:

# #![allow(unused_variables)]
#fn main() {
for i in 1..11 {
    println!("{}", i);
}
#}