Provider completion for namespaced functions after single colon

[ansgarm]

Background

Namespaced functions in HCL that are not complete (e.g. provider::aws, a::, or a::b) return a ExprSyntaxError expression as long as there are no parentheses. However, if there's only one colon (e.g. a::b: or see gif below), hcl parses this differently and does not return an ExprSyntaxError for the position after the single colon.

Proposal

Either try to do some better recovery for these cases (tbd how) or find a fix in hcl that could catch these cases and allow looking for single colons when already parsing a namespaced function (this might only work after the first double colon though).