cue: back-quoted identifier literals

[mpvl]

There is currently no way to reference a top-level field with a non-standard character:

"foo-bar": "can't touch this"

a: // cannot reference "foo-bar"

One solution is to introduce $ to refer to the root object. This is possible, but such references often result in poor configuration file design. It is also one other thing to learn for a user.

An alternative approach is to allow a syntax for identifiers with non-standard characters. Swift and GCL allow back quotes for this purpose:

"foo-bar": "can touch this"

a: `foo-bar`

Main drawback: now we have three ways of referring to identifiers. Allowing back quotes also on the left hand side might mitigate this issue. The string approach may be considered a relic of JSON and hardly used unless needed for interpolation.

`foo-bar`: "can touch this"

a: `foo-bar`

"dynamic\(interpolated)": 42

cue fmt could be used to canonicalize LHS identifiers according to this rule.

[mpvl]

The new aliases provide a better alternative. Closing.

[cueckoo]

This issue has been migrated to cue-lang/cue#2.

For more details about CUE's migration to a new home, please see cue-lang/cue#1078.