Fix parsing of [a~b] (#137)

In space sensitive contexts, `~` is parsed as unary or binary depending
on whitespace to the left and right of the `~`. In this case it should
be binary and parse as `(ref (call-i ~ a b))`

Author: c42f

src/parser.jl

@@ -566,14 +566,15 @@ function parse_assignment_with_initial_ex(ps::ParseState, mark, down::T) where {
         return
     end
     if k == K"~"
-        if ps.space_sensitive && !preceding_whitespace(peek_token(ps, 2))
+        if ps.space_sensitive && preceding_whitespace(t) && !preceding_whitespace(peek_token(ps, 2))
             # Unary ~ in space sensitive context is not assignment precedence
             # [a ~b]  ==>  (hcat a (call-pre ~ b))
             return
         end
         # ~ is the only non-syntactic assignment-precedence operator.
         # a ~ b      ==>  (call-i a ~ b)
         # [a ~ b c]  ==>  (hcat (call-i a ~ b) c)
+        # [a~b]      ==>  (vect (call-i a ~ b))
         bump(ps)
         parse_assignment(ps, down)
         emit(ps, mark, K"call", INFIX_FLAG)

test/parser.jl

@@ -51,6 +51,7 @@ tests = [
         "[a ~b]"      =>  "(hcat a (call-pre ~ b))"
         "a ~ b"       =>  "(call-i a ~ b)"
         "[a ~ b c]"   =>  "(hcat (call-i a ~ b) c)"
+        "[a~b]"       =>  "(vect (call-i a ~ b))"
     ],
     JuliaSyntax.parse_pair => [
         "a => b"  =>  "(call-i a => b)"