[feedback][eldritchv0.3] span error

[hulto]

Is your feedback related to a problem? Please describe.

>>> a = 1
>>> b = []
>>> a =+ 1
Error: Parser Error: Expect expression. Found Token { kind: Plus, span: Span { start: 3, end: 4, line: 1 } }

>>> a++
Error: Parser Error: Expect expression. Found Token { kind: Plus, span: Span { start: 2, end: 3, line: 1 } }

>>> a = 2
>>> b = []
>>> a => b
Error: Parser Error: Expect expression. Found Token { kind: Gt, span: Span { start: 3, end: 4, line: 1 } }

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