golang/go

x/tools/gopls/internal/analysis/modernize: add pass to use reflect.TypeAssert

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#75,422 opened on Sep 11, 2025

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AnalysisFeatureRequestToolsgoplshelp wanted

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Description

https://go.dev/cl/702735 replaced v.Interface().(T) with reflect.TypeAssert[T](v), where v is a reflect.Value, and demonstrated a significant performance improvement. Although the new code is 7 chars longer, it is more direct and arguably clearer. We should add a modernizer to automate this transformation when v.Interface().(T) appears in a two-value (x, ok := ...) context in a file using go1.25 or later. The doc comment for TypeAssert states that they are "semantically equivalent".

Contributor guide

Research direction
Study the existing modernizer passes in x/tools/gopls/internal/analysis/modernize to understand the pattern, then implement a new pass that matches the two value form of v.Interface().(T) and replaces it with reflect.TypeAssert[T](v). Ensure the transform only applies when the file uses go1.25 or later.
Tech stack
go
Domain
tooling
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Go
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65