"Parse don't validate is suboptimal"

What you ideally want is a first step that "validates", i.e. creates a representation from text that is easy to use but also succeeds for any input, and then a further "parsing" step that converts it to another representation such that the parsing only succeeds for valid input and is invertible for any value of the representation type, and then finally code that checks constraints that aren't captured by the type system.

This way you can support IDEs that need to edit partially incorrect code.