Fix encode and decode bug for binary ast

[quininer]

I encountered two bugs while using binary ast.

1. when FunctionDeclaration.parameter is empty but not nil, it will occupy a slot but will not generate correspond node.
2. getOrCreateChildAtNodeIndex assume a linear layout, but that's not true. like

console.log("hello world")

// PropertyAccessExpression(23) @42..56
//   Identifier(24) @42..52 "console"
//   Identifier(25) @53..56 "log"
// NodeList(26) @57..73
//   StringLiteral(27) @57..70 "hello world"

I provided the correspond tests and fixes in PR, but I don't think the fixes here are optimal. it primarily serves as a means of revealing the cause of a bug.

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[Copilot]

Pull Request Overview

This PR fixes a bug in the encoder/decoder protocol for AST nodes. The fix addresses how empty parameter lists are handled for FunctionDeclaration nodes, ensuring the bitmask correctly indicates when the parameters property should be included in the child node structure.

• Updated FunctionDeclaration encoding to check if parameters are both non-nil and non-empty
• Implemented a new getChildAtNodeIndex method that walks children by index without caching
• Updated getNamedChild to use the new uncached child lookup method
• Added a test case validating function declaration with console.log call

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
internal/api/encoder/encoder.go	Modified FunctionDeclaration encoder to check for both non-nil and non-empty parameters when setting the child bitmask
_packages/api/src/node.ts	Added getChildAtNodeIndex method to retrieve children without caching; updated getNamedChild to use the new uncached method
_packages/api/test/api.test.ts	Added new test case for function declarations with multiple arguments to validate the fix

[Copilot]

The FunctionDeclaration case now checks for both non-nil and non-empty parameters, but other similar function-like constructs (lines 485, 488, 491, 494, 497, 500, 503, 506, 521, 524, 596, 599, 689) only check for != nil. This inconsistency could lead to similar bugs with CallSignature, ConstructSignature, Constructor, GetAccessor, SetAccessor, IndexSignature, MethodSignature, MethodDeclaration, ArrowFunction, FunctionExpression, and other function-like nodes. Consider applying the same empty check (len(n.Parameters.Nodes) > 0) to all node types with Parameters properties for consistency.

[Copilot]

Commented-out code should be removed. If this line is being kept temporarily for reference during development, it should be removed before merging to keep the codebase clean.

Suggested change

// return this.getOrCreateChildAtNodeIndex(this.index + 1 + propertyIndex);

[Copilot]

The new getChildAtNodeIndex method is missing documentation. Add a JSDoc comment explaining its purpose, parameters (parent - the parent node index, index - the child's ordinal position), return value, and how it differs from getOrCreateChildAtNodeIndex (specifically that it doesn't cache children).