assert: make tHelper a type alias

[dolmen]

Summary

The tHelper interface is defined only for internal usage. We don't need a "hard" type for it as we don't define methods on it. Let's make is just a alias to the anonymous interface it represents.

Note: we are already using type aliases elswhere, and type aliases were introduced a long time ago in Go 1.9.

Changes

• assert: tHelper becomes a type alias
• require: tHelper becomes a type alias

Motivation

The tHelper symbol is not needed at runtime. This should reduce resource usage (yes, negligible).

Related issues

• assert: add Helper() in TestingT interface #1422 is also related to the interface { Helper() } type, but not dependent

[brackendawson]

You would normally do this to facilitate moving/combining previously declared types, which we aren't. If there is a performance difference, it is too small to measure. But I have no other reason to object to this.

Benchmarks

type impl struct{}

func (impl) Helper() {
	_ = math.Abs(-1)
}

func BenchmarkTypeAssertionWithDeclaredType(b *testing.B) {
	type helper interface {
		Helper()
	}

	var t any = &impl{}

	for i := 0; i < b.N; i++ {
		if t, ok := t.(helper); ok {
			t.Helper()
		}
	}
}

func BenchmarkTypeAssertionWithTypeAlias(b *testing.B) {
	type helper = interface {
		Helper()
	}

	var t any = &impl{}

	for i := 0; i < b.N; i++ {
		if t, ok := t.(helper); ok {
			t.Helper()
		}
	}
}

goos: darwin
goarch: arm64
pkg: github.com/brackendawson/kata
BenchmarkTypeAssertionWithDeclaredType-10       525305594                2.220 ns/op           0 B/op          0 allocs/op
BenchmarkTypeAssertionWithTypeAlias-10          544804904                2.235 ns/op           0 B/op          0 allocs/op
PASS
ok      github.com/brackendawson/kata   2.963s

[dolmen]

@brackendawson There is no significant performance improvement (or degradation) expected. The resource usage I claim is just the absence of the type definition in the final binary, so a smaller binary.

Compare the output of this command on this branch vs master:

$ (cd assert ; go test -c && strings assert.test | grep BoolAssertionFunc)