Golang SelectorExpr.Pos方法代码示例

// compiles a selector statement like x.sel
func (w *World) compileSelectorStmt(n *ast.SelectorExpr) Expr {
	x := w.compileExpr(n.X)
	t := x.Type()

	if t == nil {
		panic(err(n.Pos(), "void does not have member", n.Sel.Name))
	}

	sel := strings.ToLower(n.Sel.Name)
	N := ""
	for i := 0; i < t.NumMethod(); i++ {
		name := t.Method(i).Name
		if strings.ToLower(name) == sel && unicode.IsUpper(rune(name[0])) && !strings.HasSuffix(name, GoExclusiveMethodSuffix) {
			N = t.Method(i).Name
			break
		}
	}
	if N == "" {
		panic(err(n.Pos(), t, "has no method", n.Sel.Name))
	}
	return &selector{x, N}
}

func (check *checker) selector(x *operand, e *ast.SelectorExpr) {
	// these must be declared before the "goto Error" statements
	var (
		obj      Object
		index    []int
		indirect bool
	)

	sel := e.Sel.Name
	// If the identifier refers to a package, handle everything here
	// so we don't need a "package" mode for operands: package names
	// can only appear in qualified identifiers which are mapped to
	// selector expressions.
	if ident, ok := e.X.(*ast.Ident); ok {
		if pkg, _ := check.scope.LookupParent(ident.Name).(*PkgName); pkg != nil {
			check.recordUse(ident, pkg)
			pkg.used = true
			exp := pkg.pkg.scope.Lookup(sel)
			if exp == nil {
				if !pkg.pkg.fake {
					check.errorf(e.Pos(), "%s not declared by package %s", sel, ident)
				}
				goto Error
			}
			if !exp.Exported() {
				check.errorf(e.Pos(), "%s not exported by package %s", sel, ident)
				// ok to continue
			}
			check.recordSelection(e, PackageObj, nil, exp, nil, false)
			// Simplified version of the code for *ast.Idents:
			// - imported objects are always fully initialized
			switch exp := exp.(type) {
			case *Const:
				assert(exp.Val() != nil)
				x.mode = constant
				x.typ = exp.typ
				x.val = exp.val
			case *TypeName:
				x.mode = typexpr
				x.typ = exp.typ
			case *Var:
				x.mode = variable
				x.typ = exp.typ
			case *Func:
				x.mode = value
				x.typ = exp.typ
			case *Builtin:
				x.mode = builtin
				x.typ = exp.typ
				x.id = exp.id
			default:
				unreachable()
			}
			x.expr = e
			return
		}
	}

	check.exprOrType(x, e.X)
	if x.mode == invalid {
		goto Error
	}

	obj, index, indirect = LookupFieldOrMethod(x.typ, check.pkg, sel)
	if obj == nil {
		if index != nil {
			// TODO(gri) should provide actual type where the conflict happens
			check.invalidOp(e.Pos(), "ambiguous selector %s", sel)
		} else {
			check.invalidOp(e.Pos(), "%s has no field or method %s", x, sel)
		}
		goto Error
	}

	if x.mode == typexpr {
		// method expression
		m, _ := obj.(*Func)
		if m == nil {
			check.invalidOp(e.Pos(), "%s has no method %s", x, sel)
			goto Error
		}

		// verify that m is in the method set of x.typ
		if !indirect && ptrRecv(m) {
			check.invalidOp(e.Pos(), "%s is not in method set of %s", sel, x.typ)
			goto Error
		}

		check.recordSelection(e, MethodExpr, x.typ, m, index, indirect)

		// the receiver type becomes the type of the first function
		// argument of the method expression's function type
		var params []*Var
		sig := m.typ.(*Signature)
		if sig.params != nil {
			params = sig.params.vars
		}
		x.mode = value
		x.typ = &Signature{
			params:   NewTuple(append([]*Var{NewVar(token.NoPos, check.pkg, "", x.typ)}, params...)...),
//.........这里部分代码省略.........