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package parser
import (
"errors"
"fmt"
"reflect"
"strings"
"github.com/mvertes/parscan/lang"
)
type typeFlag int
const (
parseTypeIn typeFlag = iota
parseTypeOut
parseTypeVar
parseTypeType
)
var (
InvalidTypeErr = errors.New("invalid type")
MissingTypeErr = errors.New("missing type")
SyntaxErr = errors.New("syntax error")
TypeNotImplementedErr = errors.New("not implemented")
)
// ParseTypeExpr parses a list of tokens defining a type expresssion and returns
// the corresponding runtime type or an error.
func (p *Parser) ParseTypeExpr(in Tokens) (typ reflect.Type, err error) {
switch in[0].Id {
case lang.BracketBlock:
typ, err := p.ParseTypeExpr(in[1:])
if err != nil {
return nil, err
}
if b := in[0].Block(); len(b) > 0 {
x, err := p.Scan(b, false)
if err != nil {
return nil, err
}
cval, _, err := p.evalConstExpr(x)
if err != nil {
return nil, err
}
size, ok := constValue(cval).(int)
if !ok {
return nil, fmt.Errorf("invalid size")
}
return reflect.ArrayOf(size, typ), nil
}
return reflect.SliceOf(typ), nil
case lang.Mul:
typ, err := p.ParseTypeExpr(in[1:])
if err != nil {
return nil, err
}
return reflect.PointerTo(typ), nil
case lang.Func:
// Get argument and return token positions depending on function pattern:
// method with receiver, named function or anonymous closure.
// TODO: handle variadics
var out Tokens
var indexArgs int
switch l, in1 := len(in), in[1]; {
case l >= 4 && in1.Id == lang.ParenBlock && in[2].Id == lang.Ident:
indexArgs, out = 3, in[4:]
case l >= 3 && in1.Id == lang.Ident:
indexArgs, out = 2, in[3:]
case l >= 2 && in1.Id == lang.ParenBlock:
indexArgs, out = 1, in[2:]
default:
return nil, fmt.Errorf("invalid func signature")
}
// We can now parse function input and output parameter types.
// Input parameters are always enclosed by parenthesis.
iargs, err := p.Scan(in[indexArgs].Block(), false)
if err != nil {
return nil, err
}
arg, _, err := p.parseParamTypes(iargs, parseTypeIn)
if err != nil {
return nil, err
}
// Output parameters may be empty, or enclosed or not by parenthesis.
if len(out) == 1 && out[0].Id == lang.ParenBlock {
if out, err = p.Scan(out[0].Block(), false); err != nil {
return nil, err
}
}
ret, _, err := p.parseParamTypes(out, parseTypeOut)
if err != nil {
return nil, err
}
return reflect.FuncOf(arg, ret, false), nil
case lang.Ident:
// TODO: selector expression (pkg.type)
s, _, ok := p.getSym(in[0].Str, p.scope)
if !ok || s.kind != symType {
return nil, fmt.Errorf("%w: %s", InvalidTypeErr, in[0].Str)
}
return s.Type, nil
case lang.Struct:
if len(in) != 2 || in[1].Id != lang.BraceBlock {
return nil, fmt.Errorf("%w: %v", SyntaxErr, in)
}
if in, err = p.Scan(in[1].Block(), false); err != nil {
return nil, err
}
var fields []reflect.StructField
for _, lt := range in.Split(lang.Semicolon) {
types, names, err := p.parseParamTypes(lt, parseTypeType)
if err != nil {
return nil, err
}
for i, name := range names {
fields = append(fields, reflect.StructField{Name: "X" + name, Type: types[i]})
// TODO: handle embedded fields
}
}
return reflect.StructOf(fields), nil
default:
return nil, fmt.Errorf("%w: %v", TypeNotImplementedErr, in[0].Name())
}
}
// parseParamTypes parses a list of comma separated typed parameters and returns a list of
// runtime types. Implicit parameter names and types are supported.
func (p *Parser) parseParamTypes(in Tokens, flag typeFlag) (types []reflect.Type, vars []string, err error) {
// Parse from right to left, to allow multiple comma separated parameters of the same type.
list := in.Split(lang.Comma)
for i := len(list) - 1; i >= 0; i-- {
t := list[i]
if len(t) == 0 {
continue
}
param := ""
local := p.funcScope != ""
if p.hasFirstParam(t) {
param = strings.TrimPrefix(p.scope+"/"+t[0].Str, "/")
t = t[1:]
if len(t) == 0 {
if len(types) == 0 {
return nil, nil, MissingTypeErr
}
// Type was ommitted, apply the previous one from the right.
types = append([]reflect.Type{types[0]}, types...)
p.addSymVar(i, param, types[0], flag, local)
vars = append(vars, param)
continue
}
}
typ, err := p.ParseTypeExpr(t)
if err != nil {
return nil, nil, err
}
if param != "" {
p.addSymVar(i, param, typ, flag, local)
}
types = append([]reflect.Type{typ}, types...)
vars = append(vars, param)
}
return types, vars, err
}
func (p *Parser) addSymVar(index int, name string, typ reflect.Type, flag typeFlag, local bool) {
zv := reflect.New(typ).Elem()
switch flag {
case parseTypeIn:
p.addSym(-index-2, name, zv, symVar, typ, true)
case parseTypeOut:
p.addSym(p.framelen[p.funcScope], name, zv, symVar, typ, true)
p.framelen[p.funcScope]++
case parseTypeVar:
if !local {
p.addSym(unsetAddr, name, zv, symVar, typ, local)
break
}
p.addSym(p.framelen[p.funcScope], name, zv, symVar, typ, local)
p.framelen[p.funcScope]++
}
}
// hasFirstParam returns true if the first token of a list is a parameter name.
func (p *Parser) hasFirstParam(in Tokens) bool {
if in[0].Id != lang.Ident {
return false
}
s, _, ok := p.getSym(in[0].Str, p.scope)
return !ok || s.kind != symType
}
|
