Support line continuation

[luis-j-soares]

A future OS release will introduce automatic line continuation in BrightScript, allowing expressions and function call arguments to span multiple lines after binary operators (+, -, *, /, \, mod, ^, and, or, and relational operators).

This PR adds parser support for that syntax behind an allowLineContinuation flag.

Behaviour

• Always enabled in .bs files (BrighterScript mode)
• Opt-in for .brs files via the new allowLineContinuation: true config option (or --allow-line-continuation on the CLI)
• Also enabled implicitly when allowBrighterScriptInBrightScript is set, since that already forces BrighterScript mode

Examples

Arithmetic operators

result = value1 +
         value2 *
         value3

ratio = totalWidth -
        padding /
        columns

Boolean operators

condition = isValid and
            isEnabled or
            isRequired

Relational operators

isInRange = x >=
            minValue and
            x <=
            maxValue

Chained across multiple lines

total = basePrice +
        tax +
        shippingCost -
        discount

Function call arguments split across lines

result = calculateValue(
    param1,
    param2
)

Inline objects as arguments (supported since BrightScript's inception — unaffected by this flag)

foo({
    option1: true,
    option2: false
})

[markwpearce]

Will we need to update the formatter as well?

[luis-j-soares]

Will we need to update the formatter as well?

@markwpearce I would say so. I can open an issue and work on it once this PR is merged.