proposal: reflect: DeepEqual to consider identical function pointers as equal

[iwahbe]

Proposal Details

Currently, reflect.DeepEqual considers all non-nil functions as un-equal, even if they are the same function:

go/src/reflect/deepequal.go

Lines 154 to 159 in 1a93e4a

	case Func:
	if v1.IsNil() && v2.IsNil() {
	return true
	}
	// Can't do better than this:
	return false

reflect.DeepEqual should be extended to consider identical functions as equal:

 case Func: 
 	return v1.Pointer() == v2.Pointer()

This would allow users to assert that one struct "is" another struct:

func TestRoundTrip(x T) {
 	if !reflect.DeepEqual(x, blackBox(x)) {
 	 	panic("not equal")
 	}
}

That identical functions are not equal is surprising.

[gabyhelp]

Related Issues

• reflect: DeepEqual should ignore non nil functions #8554 (closed)
• reflect: fix deep equal bug on comparing func types #27758 (closed)
• Proposal: reflect: DeepEqual with predicates map #30066 (closed)
• proposal: reflect: add support for `Equal(T) bool` method in `DeepEqual()` #20444 (closed)
• reflect/DeepEqual: remove redundant type equality check #33291 (closed)
• reflect: DeepEqual can return true for values that are not equal #39607 (closed)
• reflect.DeepEqual panics on function comparisons #3122 (closed)

Related Code Changes

• reflect: fix deep equal bug on comparing func types
• reflect: add new API to check equality

Related Documentation

• Package reflect > func DeepEqual ¶

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[seankhliao]

DeepEqual reflects the capabilities of the language, and functions are not comparable types.

closing as infeasible