hnix permits indented strings as attribute names

[sjakobi]

nix-repl> { ''x'' = 0; }.x 
error: syntax error, unexpected IND_STRING_OPEN, at (string):1:3

hnix> { ''x'' = 0; }.x
0

Is this a bug?

[sjakobi]

This is the relevant type:

hnix/src/Nix/Expr/Types.hs

Lines 268 to 271 in 704323e

	data NKeyName r
	= DynamicKey !(Antiquoted (NString r) r)
	| StaticKey !VarName
	deriving (Eq, Ord, Generic, Typeable, Data, Show, Read, NFData, Hashable)

And here's some parser output:

> parseNixText "{ ''x'' = 0; }"
Success (Fix (NSet NNonRecursive [NamedVar (DynamicKey (Plain (Indented 0 [Plain "x"])) :| []) (Fix (NConstant (NInt 0))) (SourcePos {sourceName = "<string>", sourceLine = Pos 1, sourceColumn = Pos 3})]))

I think the problem is that by using (NString r) for the string type in DynamicKey's Antiquoted field, we also allow Indented strings.

I wonder whether a solution would be to split NString:

newtype DoubleQuoted r = DoubleQuoted [Antiquoted Text r]
data Indented r = Indented Int [Antiquoted Text r]
data NString r = DoubleQuoted' (DoubleQuoted r) | Indented' (Indented r)

Then we could define DynamicKey like this:

 data NKeyName r 
   = DynamicKey !(Antiquoted (DoubleQuoted r) r) 
   | StaticKey !VarName