parseUriTemplateVarSpec

private fnUriTemplateVarSpec parseUriTemplateVarSpec(string exprStr, ref size_t i, size_t basePos) @safe

Parse a varspec starting at i inside an expression.

`exprStr`	Expression body.
`i`	Current position inside `exprStr` (advanced past the varspec).
`basePos`	Byte offset in the original template, used for error reporting.

The parsed UriTemplateVarSpec.

UriTemplateException on invalid syntax.