`ExprConcatStrings` tracks whether the expression is an interpolation or
not via an obscure boolean called `forceString`.
Instead, we rename it to `isInterpolation`.
This is a breaking change for the JSON AST representation.
Change-Id: I9f89337449b56f6e99a961e21169761f554c9896
Signed-off-by: Raito Bezarius <raito@lix.systems>
The code for serialization Expr nodes back into (pseudo-)Nix has been
removed for being subtly error-prone and tedious to maintain. Instead,
`nix-instantiate --parse` now prints a JSON representation of the AST.
Usage patterns of the --parse flag I've found in the wild:
1. Check if a file is well-formed, i.e. discard output and test exit code
2. Get parser errors from a file, i.e. discard stdout and use stderr
3. Nixfmt uses --parse to test equivalence pre/post format, and that property is (should be?) preserved
None of these should break with the current change
Closes#487
Change-Id: Icdbaad17790f2ad8765fa08e02e6597ee4c7a909
It was never intended to be a feature to be used, and moreover it is
inconsistent: One cannot override `+`, and overriding `__lessThan` won't
affect the builtins which do comparisons.
Change-Id: Iaba54a05aa4c2eb37cdb3dc0d731fcee5a86deba
Raito Bezarius