Generic function support

[suzmue]

Filing this issue to track/ discuss generic function support for gotests.

Currently, gotests produces a table driven test for a function with type parameters, but the test needs to actually be modified to include concrete types (the test file will have build errors).

Example:

typeparams.go:

package typeparams

// SumIntsOrFloats sums the values of map m. It supports both floats and integers
// as map values.
func SumIntsOrFloats[K comparable, V int64 | float64](m map[K]V) V {
	var s V
	for _, v := range m {
		s += v
	}
	return s
}

typeparams_test.go:

package typeparams

import (
	"reflect"
	"testing"
)

func TestSumIntsOrFloats(t *testing.T) {
	type args struct {
		m map[K]V // K and V not defined
	}
	tests := []struct {
		name string
		args args
		want V
	}{
		// TODO: Add test cases.
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			if got := SumIntsOrFloats(tt.args.m); !reflect.DeepEqual(got, tt.want) {
				t.Errorf("SumIntsOrFloats() = %v, want %v", got, tt.want)
			}
		})
	}
}

Can better table driven tests be generated for functions with type params / should the generated tests make sure there are no build errors?

Related go issue: golang/go#50558

[KevinSnyderCodes]

For some inputs, gotests fails to generate tests:

typeparams.go

package typeparams

type Set[T comparable] struct {
	m map[T]struct{}
}

func (o *Set[T]) Add(v T) {
	o.m[v] = struct{}{}
}

func (o *Set[T]) Has(v T) bool {
	_, ok := o.m[v]
	return ok
}

gotests output:

output.Process: imports.Process: /var/folders/fw/grysx2h56354vh4_30px6_r80000gp/T/gotests_112301585:9:14: all type parameters must be named (and 1 more errors)