Function StructTypeField

symbols/typeexprs.go:214–251

StructTypeField returns field type for given field.

(tpe ast.BaseTerm, field ast.Constant)

// StructTypeField returns field type for given field.
func StructTypeField(tpe ast.BaseTerm, field ast.Constant) (ast.BaseTerm, error) {
	if IsUnionTypeExpression(tpe) { // Project
		src, _ := UnionTypeArgs(tpe)
		alternatives := []ast.BaseTerm{}
		for _, s := range src {
			projected, err := StructTypeField(s, field)
			if err != nil {
				continue
			}
			alternatives = append(alternatives, projected)
		}
		if len(alternatives) == 1 {
			return alternatives[0], nil
		}
		return NewUnionType(alternatives...), nil
	}
	if debug && !IsStructTypeExpression(tpe) {
		return nil, fmt.Errorf("not a struct type expression: %v", tpe)
	}
	elems := typeArgs(tpe)
	for i := 0; i < len(elems); i++ {
		var key ast.BaseTerm
		arg := elems[i]
		if IsOptional(arg) {
			key = arg.(ast.ApplyFn).Args[0]
		} else {
			key = arg
		}
		if key.Equals(field) {
			if IsOptional(arg) {
				return arg.(ast.ApplyFn).Args[1], nil
			}
			i++
			return elems[i], nil
		}
	}
	return nil, fmt.Errorf("no field %v in %v", field, tpe)
}

// FunTypeResult returns result type of function type.
func FunTypeResult(tpe ast.BaseTerm) (ast.BaseTerm, error) {