You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: shader.go
    path of file: ./repos/ebiten/internal/shader
    
    the code of the file until where you have to start completion: // Copyright 2020 The Ebiten Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package shader

import (
	"bufio"
	"bytes"
	"fmt"
	"go/ast"
	gconstant "go/constant"
	"go/parser"
	"go/token"
	"regexp"
	"strings"

	"github.com/hajimehoshi/ebiten/v2/internal/shaderir"
)

type variable struct {
	name           string
	typ            shaderir.Type
	forLoopCounter bool
}

type constant struct {
	name  string
	typ   shaderir.Type
	value gconstant.Value
}


    
func (cs *compileState) parseFuncParams(block *block, fname string, d *ast.FuncDecl) (in, out []variable, ret shaderir.Type) {
	for _, f := range d.Type.Params.List {
		t, ok := cs.parseType(block, fname, f.Type)
		if !ok {
			return
		}
		for _, n := range f.Names {
			in = append(in, variable{
				name: n.Name,
				typ:  t,
			})
		}
	}

	if d.Type.Results == nil {
		return
	}

	for _, f := range d.Type.Results.List {
		t, ok := cs.parseType(block, fname, f.Type)
		if !ok {
			return
		}
		if len(f.Names) == 0 {
			out = append(out, variable{
				name: "",
				typ:  t,
			})
		} else {
			for _, n := range f.Names {
				out = append(out, variable{
					name: n.Name,
					typ:  t,
				})
			}
		}
	}

	// If there is only one returning value, it is treated as a returning value.
	// An array cannot be a returning value, especially for HLSL (#2923).
	if len(out) == 1 && out[0].name == "" && out[0].typ.Main != shaderir.Array {
		ret = out[0].typ
		out = nil
	}

	return
}