Add named argument support and duplicate parameter name warning

[chrisdp]

Summary

• Named arguments: allows calling functions using named parameter syntax (e.g. greet(name: "Bob"))
  • Validates unknown named arguments against the function definition
  • Errors on duplicate named arguments in the same call
  • Errors on positional arguments following named arguments
  • Errors when named args are used on an unknown function (can't verify param names)
• Duplicate parameter warning: emits a warning (code 1150) when a function/sub definition has two or more parameters with the same name (case-insensitive)
• Fixes Expression import in Scope.ts to pull from parser/AstNode where it is declared

New diagnostic codes

Code	Severity	Message
1146	Error	Unknown named argument '{name}' for function '{func}'
1147	Error	Named argument '{name}' was already provided
1148	Error	Positional arguments cannot follow named arguments
1149	Error	Cannot use named arguments when calling '{func}' because the function definition cannot be found
1150	Warning	Duplicate parameter name '{name}'

Test plan

• Named argument tests in src/parser/tests/expression/NamedArgument.spec.ts
• Duplicate parameter tests in src/files/BrsFile.spec.ts

🤖 Generated with Claude Code

[TwitchBronBron]

We need to change a few things about this:

• named arguments should be evaluted in the order they are written in the text. So that will require some hoisting to local __bs* vars. only need to hoist up until the last call expression. (and can likely skip hoisting VariableExpression and literals (maybe even AA and Array literals as long as they're only composed of literals or VariableExpressions themselves)
• sequence the local hoisted vars on a per-function basis. (maybe use a WeakMap to use the functionExpression as the key and the sequence as the value)?
• move the code into ScopeValidator.ts instead of living in Scope.ts
• the transpiler should be the one responsible for reordering the args, and only on the way out....we don't want to manipulate the AST for this if we can help it, because that makes things complicated for other plugins earlier and later in the flow.
• instead of modifying the transpiler directly, we should do similar to the Ternary transpilation. We modify the CallExpression arguments array during the beforeFileTranspile (see BrsFilePreTranspileProcessor)

[TwitchBronBron]

Remove this, we don't want to be caching this type of information.

[Copilot]

Addressed in de7a040. Removed the prior named-arg transpile complexity and any call-expression-level cached mapping behavior; named-arg handling now validates order in ScopeValidator and rewrites directly in pre-transpile.

[TwitchBronBron]

move this into ScopeValidator.ts

[Copilot]

Done in de7a040. Named-argument validation is handled in ScopeValidator.ts, and the Scope-level function-call count path now defers named-arg cases to that validator.

[chrisdp]

@luis-j-soares doesn't need to be. Just means the amount of places that it can be used in isn't quite as many as it would be in v1. But since this is just a call site feature it can be expanded on in v1 to support more locations.

[chrisdp]

@copilot i want to update this pr to remove the param reordering for now.

Enforce the order of params

If someone were to do something like this example we would transpile and populated the missing optional details for them.

sub greet(name = “Unknown” as string, excited = false as boolean)
    if excited
        print "Hello, " + name + "!!!"
    else
        print "Hello, " + name
    end if
end sub

sub main()
    greet(excited: true)
end sub

So greet would become:

greet("Unknown", true)

[Copilot]

@copilot i want to update this pr to remove the param reordering for now.

Enforce the order of params...

Implemented in de7a040. Named arguments now enforce declaration order, and transpilation no longer does hoisting/IIFE reordering. Calls like greet(excited: true) now transpile to greet("Unknown", true) by filling skipped leading optional params.

We need to change a few things about this:

• named arguments should be evaluted in the order they are written in the text. So that will require some hoisting to local __bs* vars. only need to hoist...

Updated in de7a040 based on the latest direction to remove param reordering for now: named args are enforced in declaration order, validation lives in ScopeValidator.ts, and pre-transpile now performs a direct named→positional rewrite (including default backfill for skipped leading optional params) without hoisting/IIFE logic.

[chrisdp]

@copilot lets also have code actions available to the user to to fix the order.

[Copilot]

@copilot lets also have code actions available to the user to to fix the order.

Implemented in f04129a (with core functionality in 1604dce): added a quick-fix code action, Reorder named arguments to match function declaration, for out-of-order named-arg diagnostics so users can auto-fix argument order at the callsite.