Resolve function calls consistently inside ClosedExpression binding

[Seddryck]

Bug

Function calls inside a ClosedExpression are not resolved using the same function catalog/binding context as function calls inside an OpenExpression.

Reproduction

The equivalent nested function call binds successfully when represented as an OpenExpression:

.\expressif bind 'even |or greater-than(add(17))'

Result:

OpenExpression
└─ Function: or
   ├─ Arg[0]: OpenExpression
   │  └─ Function: even
   └─ Arg[1]: OpenExpression
      └─ Function: greater-than
         └─ Arg[0]: OpenExpression
            └─ Function: add
               └─ Arg[0]: Literal = 17

But the same function call fails when it is part of a ClosedExpression:

.\expressif bind 'even |or greater-than(45 | add(17))'

Result:

Unknown function 'add'.

The parser correctly produces a ClosedExpression:

.\expressif parse 'even |or greater-than(45 | add(17))'

OpenExpression
└─ BinaryExpression
   ├─ FunctionCall: even
   ├─ BinaryOperator: OR
   └─ FunctionCall: greater-than
      └─ PositionalArgument
         └─ ClosedExpression
            ├─ NumericLiteral: 45
            └─ FunctionCall: add
               └─ PositionalArgument
                  └─ NumericLiteral: 17

Expected behavior

Function calls nested inside a ClosedExpression should be resolved through the same function catalog and binding context as function calls nested inside an OpenExpression.

The following should therefore bind successfully:

greater-than(45 | add(17))

and add should resolve to the same bound function implementation as it does in:

greater-than(add(17))

Scope

• Ensure ClosedExpression binding carries the same function catalog/resolution context as OpenExpression binding.
• Add regression tests covering function calls nested in closed expressions.
• Include at least one comparison showing equivalent function resolution in open and closed expression arguments.

[Seddryck]

Reviewed as part of 2.0