[Bug]: The parser does not create diagnostics for int/float literals with more than one sign characters

[nipunayf]

Description

As mentioned in the spec, there can be only zero or one sign character prefixed to an integer or float. However, the parser does not generate a diagnostic when there are more than one such characters.

Steps to Reproduce

Execute the following Ballerina code.

public function main() {
    int x = -++--5;
    float y = --+-5.0;
}

Affected Version(s)

Ballerina 2201.8.4 (Swan Lake Update 8)

OS, DB, other environment details and versions

OS: macOS 14.2.1 23C71
JDK: openjdk 17.0.8 2023-07-18

Related area

-> Compilation

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[nipunayf]

The following expression is valid as it considers the unary-numeric-expr instead of a signed literal.

int x = -+-5;