Identifiers in range notation are not parsed correctly

[milibopp]

The following example fails to compile currently:

let a = 3;
for i in 0..a {
    let b = i;
}

with

<anon>:4:9: 4:12 error: expected identifier, found keyword `let`
<anon>:4         let b = i;
                 ^~~
<anon>:4:13: 4:14 error: expected `:`, found `b`
<anon>:4         let b = i;

[alexcrichton]

cc @nick29581

[milibopp]

btw replacing 0..a with (0..a) or 0..(a) makes the compiler behave correctly.

[milibopp]

Maybe this sheds some more light on it:

let a = 3;
for i in 0..a {}

Apparently the compiler parses it as for i in 0..(a {}) interpreting a {} as a structure literal.

Error:

<anon>:3:19: 3:20 error: structure literal must either have at least one field or use functional structure update syntax
<anon>:3     for i in 0..a {}
                           ^
<anon>:4:1: 4:2 error: expected `{`, found `}`
<anon>:4 }
         ^
<anon>:4:1: 4:2 help: place this code inside a block
<anon>:4 }
         ^

[dgrunwald]

Looks like the parser is replacing the restrictions with RESTRICTION_NO_DOTS when parsing the RHS of the range notation, thus deleting the RESTRICTION_NO_STRUCT_LITERAL. It should add to the existing restrictions instead of replacing them.

[huonw]

Closing as a dupe of #20241.