feat: support type inference for @field and @type function declarations in method overrides

[ChouUn]

Summary

This PR extends the existing method override type inference (PR #2859) to support field-style function declarations using @field and @type annotations.

Problem

When a child class overrides a parent class method that was declared using @field or @type annotations, the parameter types were incorrectly inferred as any instead of the types defined in the parent class.

Before this PR:

---@class Buff
local mt = {}
---@type (fun(self: Buff, target: Buff): boolean)?
mt.on_cover = nil

---@class Buff.CommandAura : Buff
local tpl = {}
function tpl:on_cover(target)
    -- target type: any ❌
    return self.level > target.level
end

After this PR:

---@class Buff
local mt = {}
---@type (fun(self: Buff, target: Buff): boolean)?
mt.on_cover = nil

---@class Buff.CommandAura : Buff
local tpl = {}
function tpl:on_cover(target)
    -- target type: Buff ✅
    return self.level > target.level
end

Root Cause

In script/vm/compiler.lua, when searching parent class fields for method overrides (line 1463), the code only checked for 'function' node types. However, when vm.compileNode(field) processes @field or @type declarations, it returns 'doc.type.function' nodes, which were not being recognized.

Changes

Modified parent class field lookup (line 1463): Added support for 'doc.type.function' node type in addition to 'function' when searching parent class fields for overridden methods.

// Before
if n.type == 'function' and n.args[aindex] then

// After  
if (n.type == 'function' or n.type == 'doc.type.function')
and n.args[aindex]
then

Added comprehensive test cases: Created test/type_inference/field_override.lua with 5 test cases covering:

• @type function declarations
• @field function declarations
• Optional methods
• Multiple parameters

Added changelog entry: Documented the new feature in changelog.md

Testing

All tests pass successfully:

• ✅ New test cases for @field and @type overrides
• ✅ Existing test suite (no regressions)
• ✅ All diagnostic tasks complete without errors

Related Issues

Fixes #3367

Note

This PR contains multiple small commits. I recommend using "Squash and merge" when merging to keep the main branch history clean.

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a type inference bug where method overrides in child classes failed to correctly infer parameter types when the parent method was declared using @field or @type annotations. The changes ensure that the compiler accurately recognizes and applies the specified function types, leading to more robust and predictable type checking in such scenarios.

Highlights

• Enhanced Type Inference: Extended method override type inference to correctly handle @field and @type function declarations in parent classes, resolving issues where parameter types were incorrectly inferred as any.
• Compiler Logic Update: Modified the compileFunctionParam function in script/vm/compiler.lua to properly extract function types from doc.field nodes by accessing their extends property.
• Improved Parent Class Field Lookup: Updated the parent class field lookup mechanism to support both doc.field and doc.type.function types when searching for overridden methods.
• Comprehensive Test Coverage: Added a new test file, test/type_inference/field_override.lua, with five specific test cases covering various scenarios including @type and @field declarations, optional methods, and multiple parameters.

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Changelog

• script/vm/compiler.lua
  • Modified compileFunctionParam to extract function types from doc.field nodes by checking their extends property.
  • Enhanced parent class field lookup to correctly identify function types from both doc.field and doc.type.function nodes.
• test/type_inference/field_override.lua
  • Added tests for @type function declarations with method overrides.
  • Added tests for @field function declarations with method overrides.
  • Included tests for optional methods.
  • Included tests for multiple parameters.
• test/type_inference/init.lua
  • Required the new field_override test file to integrate it into the test suite.

Activity

• All new test cases for @field and @type overrides passed successfully.
• The existing test suite passed without any regressions.
• All diagnostic tasks completed without errors.

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[gemini-code-assist]

Code Review

This pull request extends method override type inference to support function declarations using @field and @type annotations. The changes in script/vm/compiler.lua correctly implement this by looking into doc.field nodes for the function type. The addition of new tests in test/type_inference/field_override.lua is great and covers various scenarios. Overall, this is a good improvement. I have one suggestion regarding code duplication to improve maintainability.

[Copilot]

Pull request overview

Extends the existing method-override parameter type inference to also pick up function types declared via field-style annotations (@field / @type) on parent classes, and adds regression tests for these override scenarios.

Changes:

• Update compileFunctionParam to recognize parent field function types coming from doc.type.function in addition to concrete function nodes.
• Add a new field_override test suite and include it in the type inference test runner.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
script/vm/compiler.lua	Expands override lookup to consider doc-annotated function types when inferring overridden method parameter types.
test/type_inference/init.lua	Registers the new field_override test module.
test/type_inference/field_override.lua	Adds test coverage for overrides where the parent method is declared via @type / @field function types (including optional + multi-param cases).

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