Go For - Range Copy - Editing

A GoLand plugin to help developers detect an edge case: editing a range assigned variable.

Motivation

Go dictates range clause to copy collection before iterating.

Consider the following go code

package main
import "fmt"
type Editable struct{ i int }

func pumpUp(e *Editable)  {
 e.i = 100
}

func main() {
 es := []Editable { { i : 1 }, { i : 2 }, { i : 3 }, { i : 4 } }
 for _, e := range es {
 	pumpUp(&e)
 }
 fmt.Printf("%v", es)
}

below outlines the output in Go, Swift, Objective-C, Java (keeping the semantics same)

Language	Output
Go	[{1} {2} {3} {4}]
Swift	[{100} {100} {100} {100}]
Java	[{100} {100} {100} {100}]
Objective-C	[{100} {100} {100} {100}]

This plugin tries to catch such use cases and highlight them for the developer to reconsider the logic

Supported

Detect usages of pointer references of assigned variable in a for block
Detect editable method references of assigned variable in the block

To be supported

Assigned variable is predeclared before the range clause
Direct assignment of the struct's properties

* please see issues for more

Output

References

Assigned Variable = e in the above go for block

Gradle Scan: https://scans.gradle.com/s/vywyvtekrzqfg