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package parser
import (
"errors"
"fmt"
"strings"
"github.com/mvertes/parscan/lang"
"github.com/mvertes/parscan/vm"
)
type typeFlag int
const (
parseTypeIn typeFlag = iota
parseTypeOut
parseTypeVar
parseTypeType
)
// Type parsing error definitions.
var (
ErrFuncType = errors.New("invalid function type")
ErrInvalidType = errors.New("invalid type")
ErrMissingType = errors.New("missing type")
ErrSize = errors.New("invalid size")
ErrSyntax = errors.New("syntax error")
ErrNotImplemented = errors.New("not implemented")
)
func (p *Parser) parseTypeExpr(in Tokens) (typ *vm.Type, err error) {
switch in[0].Tok {
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, ErrSize
}
return vm.ArrayOf(size, typ), nil
}
return vm.SliceOf(typ), nil
case lang.Mul:
typ, err := p.parseTypeExpr(in[1:])
if err != nil {
return nil, err
}
return vm.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.Tok == lang.ParenBlock && in[2].Tok == lang.Ident:
indexArgs, out = 3, in[4:]
case l >= 3 && in1.Tok == lang.Ident:
indexArgs, out = 2, in[3:]
case l >= 2 && in1.Tok == lang.ParenBlock:
indexArgs, out = 1, in[2:]
default:
return nil, ErrFuncType
}
// 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].Tok == 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 vm.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", ErrInvalidType, in[0].Str)
}
return s.typ, nil
case lang.Struct:
if len(in) != 2 || in[1].Tok != lang.BraceBlock {
return nil, fmt.Errorf("%w: %v", ErrSyntax, in)
}
if in, err = p.Scan(in[1].Block(), false); err != nil {
return nil, err
}
var fields []*vm.Type
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, &vm.Type{Name: name, PkgPath: p.pkgName, Rtype: types[i].Rtype})
// TODO: handle embedded fields
}
}
return vm.StructOf(fields), nil
default:
return nil, fmt.Errorf("%w: %v", ErrNotImplemented, 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 []*vm.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, ErrMissingType
}
// Type was omitted, apply the previous one from the right.
types = append([]*vm.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([]*vm.Type{typ}, types...)
vars = append(vars, param)
}
return types, vars, err
}
func (p *Parser) addSymVar(index int, name string, typ *vm.Type, flag typeFlag, local bool) {
zv := vm.NewValue(typ)
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].Tok != lang.Ident {
return false
}
s, _, ok := p.getSym(in[0].Str, p.scope)
return !ok || s.kind != symType
}
// typeStartIndex returns the index of the start of type expression in tokens, or -1.
func (p *Parser) typeStartIndex(in Tokens) int {
index := len(in) - 1
for i := index; i >= 0; i-- {
switch in[i].Tok {
case lang.Ident, lang.Struct, lang.Map, lang.Func, lang.Interface, lang.Mul, lang.BraceBlock, lang.BracketBlock, lang.ParenBlock:
index = i
default:
return index
}
}
return -1
}
|
