fix: return single definition for anonymous-function field assignment

[tomlau10]

Fixes #2451

Summary

Go to definition on a field assigned an anonymous function returned two candidates on the same line — the field name and the function value.

A = {}
A.c = function() end
A.c()   -- goto definition on `c` previously returned 2 candidates: `c` and `function`

local f = function() end behaves the same way. After this PR, only the field name is returned, consistent with how literal values already behave (e.g. X.y = 1 jumps to y).

Root cause (click to expand)

vm.getDefs produces two independent defs through two paths:

1. Name candidate (c): compileByNodeChain resolves the setfield LHS, and the definition provider unwraps it via src.field.

2. Function-value candidate (function): searchByNode → compileNode merges the field's value into the compiled type. The function node survives the literal filter because function literals are explicitly exempted there — an exemption meant for generic type inference (e.g. v2 = f(function() end)), not for direct assignments.

Neither existing dedup catches it:

• node-identity dedup in getDefs treats them as different nodes;

• the nested-range dedup in sortResults only removes a target whose range contains another — these two are same-line siblings.

Fix (click to expand)

In script/core/definition.lua, after collecting targets, drop a function-value target when its owning assignment's name node is also a target:

local targetMark = {}
for _, res in ipairs(results) do
    targetMark[res.target] = true
end
for i = #results, 1, -1 do
    local target = results[i].target
    if target.type == 'function' then
        local parent = target.parent
        if parent and guide.isAssign(parent) then
            local owner = parent.field or parent.method or parent.index or parent.variable or parent
            if targetMark[owner] then
                table.remove(results, i)
            end
        end
    end
end

Why this shape:

• Conditioned on the owner also being a target, so generic-inference defs (where the function literal is the only candidate) are left untouched.

• Scoped to the definition provider only. type-definition and implementation already return a single candidate through their own filters (a type whitelist and getRefs + isAssign respectively), so they are unaffected.

Tests

• Updated test/definition/function.lua: local f = function() end now expects a single definition at f.

• Added test/definition/field.lua regression cases for both global and local tables (A.c = function() end).

• Full test suite passes.

---

中文摘要

A.c = function() end 的寫法，goto definition 原本會回傳兩個結果（欄位名稱 c 和 function 值）。此 PR 在 definition.lua 加了一段處理：當欄位名稱也在結果中時，移除冗餘的 function 值，只保留名稱節點，與 X.y = 1 跳到 y 的慣例一致。type-definition / implementation 兩個 provider 因各自已有 filter，不受影響；測試全部通過。

此 bug 的根源，是 function 字面量豁免在 2022 年某次 global-manager/infer 大型 refactor (0e159ee037) 中順手加入的，屬 refactor 的副作用、並非刻意設計；回傳 2 個 candidate 的測試也是同期的批量 update commit (9451329b33) 帶入的。

本 PR 由 Claude Code（deepseek-v4-flash）協助分析與撰寫。

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