1// Copyright 2009 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package types
6
7import (
8	"fmt"
9	"internal/goversion"
10	"internal/lazyregexp"
11	"log"
12	"strconv"
13
14	"cmd/compile/internal/base"
15)
16
17// A lang is a language version broken into major and minor numbers.
18type lang struct {
19	major, minor int
20}
21
22// langWant is the desired language version set by the -lang flag.
23// If the -lang flag is not set, this is the zero value, meaning that
24// any language version is supported.
25var langWant lang
26
27// AllowsGoVersion reports whether local package is allowed
28// to use Go version major.minor.
29func AllowsGoVersion(major, minor int) bool {
30	if langWant.major == 0 && langWant.minor == 0 {
31		return true
32	}
33	return langWant.major > major || (langWant.major == major && langWant.minor >= minor)
34}
35
36// ParseLangFlag verifies that the -lang flag holds a valid value, and
37// exits if not. It initializes data used by AllowsGoVersion.
38func ParseLangFlag() {
39	if base.Flag.Lang == "" {
40		return
41	}
42
43	var err error
44	langWant, err = parseLang(base.Flag.Lang)
45	if err != nil {
46		log.Fatalf("invalid value %q for -lang: %v", base.Flag.Lang, err)
47	}
48
49	if def := currentLang(); base.Flag.Lang != def {
50		defVers, err := parseLang(def)
51		if err != nil {
52			log.Fatalf("internal error parsing default lang %q: %v", def, err)
53		}
54		if langWant.major > defVers.major || (langWant.major == defVers.major && langWant.minor > defVers.minor) {
55			log.Fatalf("invalid value %q for -lang: max known version is %q", base.Flag.Lang, def)
56		}
57	}
58}
59
60// parseLang parses a -lang option into a langVer.
61func parseLang(s string) (lang, error) {
62	if s == "go1" { // cmd/go's new spelling of "go1.0" (#65528)
63		s = "go1.0"
64	}
65
66	matches := goVersionRE.FindStringSubmatch(s)
67	if matches == nil {
68		return lang{}, fmt.Errorf(`should be something like "go1.12"`)
69	}
70	major, err := strconv.Atoi(matches[1])
71	if err != nil {
72		return lang{}, err
73	}
74	minor, err := strconv.Atoi(matches[2])
75	if err != nil {
76		return lang{}, err
77	}
78	return lang{major: major, minor: minor}, nil
79}
80
81// currentLang returns the current language version.
82func currentLang() string {
83	return fmt.Sprintf("go1.%d", goversion.Version)
84}
85
86// goVersionRE is a regular expression that matches the valid
87// arguments to the -lang flag.
88var goVersionRE = lazyregexp.New(`^go([1-9]\d*)\.(0|[1-9]\d*)$`)
89