wit/bindgen: inconsistent generated Go names for variant cases that collide with other names

[rvolosatovs]

For WIT:

package test:repro;

interface repro {
    variant var {
        var(u8),
    }

    foo: func(var: var);
}

world imports {
    import repro;
}

wasm-tools-go 0.3.0 generates inconsistent Var accessors.

In abi.go:

func lower_Var(v Var) (f0 uint32, f1 uint32) {
	f0 = (uint32)(v.Tag())
	switch f0 {
	case 0: // var
		v1 := (uint32)(*v.Var())
		f1 = (uint32)(v1)
	}
	return
}

In repro.wit.go:

// Var_ returns a non-nil *[uint8] if [Var] represents the variant case "var".
func (self *Var) Var_() *uint8 {
	return cm.Case[uint8](self, 0)
}

See https://github.com/rvolosatovs/wasm-tools-go-var-gen-repro for a full example

Update: naming the variant some other name, matching an identifier used in the interface causes the same issue

[ydnar]

Good find. I'll take a look.