+++ /dev/null
-// Copyright 2009 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package main
-
-import (
- "fmt"
- "go/ast"
- "go/parser"
- "go/token"
- "os"
- "reflect"
- "strings"
- "unicode"
- "unicode/utf8"
-)
-
-func initRewrite() {
- if *rewriteRule == "" {
- rewrite = nil // disable any previous rewrite
- return
- }
- f := strings.Split(*rewriteRule, "->")
- if len(f) != 2 {
- fmt.Fprintf(os.Stderr, "rewrite rule must be of the form 'pattern -> replacement'\n")
- os.Exit(2)
- }
- pattern := parseExpr(f[0], "pattern")
- replace := parseExpr(f[1], "replacement")
- rewrite = func(p *ast.File) *ast.File { return rewriteFile(pattern, replace, p) }
-}
-
-// parseExpr parses s as an expression.
-// It might make sense to expand this to allow statement patterns,
-// but there are problems with preserving formatting and also
-// with what a wildcard for a statement looks like.
-func parseExpr(s, what string) ast.Expr {
- x, err := parser.ParseExpr(s)
- if err != nil {
- fmt.Fprintf(os.Stderr, "parsing %s %s at %s\n", what, s, err)
- os.Exit(2)
- }
- return x
-}
-
-// Keep this function for debugging.
-/*
-func dump(msg string, val reflect.Value) {
- fmt.Printf("%s:\n", msg)
- ast.Print(fileSet, val.Interface())
- fmt.Println()
-}
-*/
-
-// rewriteFile applies the rewrite rule 'pattern -> replace' to an entire file.
-func rewriteFile(pattern, replace ast.Expr, p *ast.File) *ast.File {
- cmap := ast.NewCommentMap(fileSet, p, p.Comments)
- m := make(map[string]reflect.Value)
- pat := reflect.ValueOf(pattern)
- repl := reflect.ValueOf(replace)
-
- var rewriteVal func(val reflect.Value) reflect.Value
- rewriteVal = func(val reflect.Value) reflect.Value {
- // don't bother if val is invalid to start with
- if !val.IsValid() {
- return reflect.Value{}
- }
- val = apply(rewriteVal, val)
- for k := range m {
- delete(m, k)
- }
- if match(m, pat, val) {
- val = subst(m, repl, reflect.ValueOf(val.Interface().(ast.Node).Pos()))
- }
- return val
- }
-
- r := apply(rewriteVal, reflect.ValueOf(p)).Interface().(*ast.File)
- r.Comments = cmap.Filter(r).Comments() // recreate comments list
- return r
-}
-
-// set is a wrapper for x.Set(y); it protects the caller from panics if x cannot be changed to y.
-func set(x, y reflect.Value) {
- // don't bother if x cannot be set or y is invalid
- if !x.CanSet() || !y.IsValid() {
- return
- }
- defer func() {
- if x := recover(); x != nil {
- if s, ok := x.(string); ok &&
- (strings.Contains(s, "type mismatch") || strings.Contains(s, "not assignable")) {
- // x cannot be set to y - ignore this rewrite
- return
- }
- panic(x)
- }
- }()
- x.Set(y)
-}
-
-// Values/types for special cases.
-var (
- objectPtrNil = reflect.ValueOf((*ast.Object)(nil))
- scopePtrNil = reflect.ValueOf((*ast.Scope)(nil))
-
- identType = reflect.TypeOf((*ast.Ident)(nil))
- objectPtrType = reflect.TypeOf((*ast.Object)(nil))
- positionType = reflect.TypeOf(token.NoPos)
- callExprType = reflect.TypeOf((*ast.CallExpr)(nil))
- scopePtrType = reflect.TypeOf((*ast.Scope)(nil))
-)
-
-// apply replaces each AST field x in val with f(x), returning val.
-// To avoid extra conversions, f operates on the reflect.Value form.
-func apply(f func(reflect.Value) reflect.Value, val reflect.Value) reflect.Value {
- if !val.IsValid() {
- return reflect.Value{}
- }
-
- // *ast.Objects introduce cycles and are likely incorrect after
- // rewrite; don't follow them but replace with nil instead
- if val.Type() == objectPtrType {
- return objectPtrNil
- }
-
- // similarly for scopes: they are likely incorrect after a rewrite;
- // replace them with nil
- if val.Type() == scopePtrType {
- return scopePtrNil
- }
-
- switch v := reflect.Indirect(val); v.Kind() {
- case reflect.Slice:
- for i := 0; i < v.Len(); i++ {
- e := v.Index(i)
- set(e, f(e))
- }
- case reflect.Struct:
- for i := 0; i < v.NumField(); i++ {
- e := v.Field(i)
- set(e, f(e))
- }
- case reflect.Interface:
- e := v.Elem()
- set(v, f(e))
- }
- return val
-}
-
-func isWildcard(s string) bool {
- rune, size := utf8.DecodeRuneInString(s)
- return size == len(s) && unicode.IsLower(rune)
-}
-
-// match reports whether pattern matches val,
-// recording wildcard submatches in m.
-// If m == nil, match checks whether pattern == val.
-func match(m map[string]reflect.Value, pattern, val reflect.Value) bool {
- // Wildcard matches any expression. If it appears multiple
- // times in the pattern, it must match the same expression
- // each time.
- if m != nil && pattern.IsValid() && pattern.Type() == identType {
- name := pattern.Interface().(*ast.Ident).Name
- if isWildcard(name) && val.IsValid() {
- // wildcards only match valid (non-nil) expressions.
- if _, ok := val.Interface().(ast.Expr); ok && !val.IsNil() {
- if old, ok := m[name]; ok {
- return match(nil, old, val)
- }
- m[name] = val
- return true
- }
- }
- }
-
- // Otherwise, pattern and val must match recursively.
- if !pattern.IsValid() || !val.IsValid() {
- return !pattern.IsValid() && !val.IsValid()
- }
- if pattern.Type() != val.Type() {
- return false
- }
-
- // Special cases.
- switch pattern.Type() {
- case identType:
- // For identifiers, only the names need to match
- // (and none of the other *ast.Object information).
- // This is a common case, handle it all here instead
- // of recursing down any further via reflection.
- p := pattern.Interface().(*ast.Ident)
- v := val.Interface().(*ast.Ident)
- return p == nil && v == nil || p != nil && v != nil && p.Name == v.Name
- case objectPtrType, positionType:
- // object pointers and token positions always match
- return true
- case callExprType:
- // For calls, the Ellipsis fields (token.Position) must
- // match since that is how f(x) and f(x...) are different.
- // Check them here but fall through for the remaining fields.
- p := pattern.Interface().(*ast.CallExpr)
- v := val.Interface().(*ast.CallExpr)
- if p.Ellipsis.IsValid() != v.Ellipsis.IsValid() {
- return false
- }
- }
-
- p := reflect.Indirect(pattern)
- v := reflect.Indirect(val)
- if !p.IsValid() || !v.IsValid() {
- return !p.IsValid() && !v.IsValid()
- }
-
- switch p.Kind() {
- case reflect.Slice:
- if p.Len() != v.Len() {
- return false
- }
- for i := 0; i < p.Len(); i++ {
- if !match(m, p.Index(i), v.Index(i)) {
- return false
- }
- }
- return true
-
- case reflect.Struct:
- for i := 0; i < p.NumField(); i++ {
- if !match(m, p.Field(i), v.Field(i)) {
- return false
- }
- }
- return true
-
- case reflect.Interface:
- return match(m, p.Elem(), v.Elem())
- }
-
- // Handle token integers, etc.
- return p.Interface() == v.Interface()
-}
-
-// subst returns a copy of pattern with values from m substituted in place
-// of wildcards and pos used as the position of tokens from the pattern.
-// if m == nil, subst returns a copy of pattern and doesn't change the line
-// number information.
-func subst(m map[string]reflect.Value, pattern reflect.Value, pos reflect.Value) reflect.Value {
- if !pattern.IsValid() {
- return reflect.Value{}
- }
-
- // Wildcard gets replaced with map value.
- if m != nil && pattern.Type() == identType {
- name := pattern.Interface().(*ast.Ident).Name
- if isWildcard(name) {
- if old, ok := m[name]; ok {
- return subst(nil, old, reflect.Value{})
- }
- }
- }
-
- if pos.IsValid() && pattern.Type() == positionType {
- // use new position only if old position was valid in the first place
- if old := pattern.Interface().(token.Pos); !old.IsValid() {
- return pattern
- }
- return pos
- }
-
- // Otherwise copy.
- switch p := pattern; p.Kind() {
- case reflect.Slice:
- if p.IsNil() {
- // Do not turn nil slices into empty slices. go/ast
- // guarantees that certain lists will be nil if not
- // populated.
- return reflect.Zero(p.Type())
- }
- v := reflect.MakeSlice(p.Type(), p.Len(), p.Len())
- for i := 0; i < p.Len(); i++ {
- v.Index(i).Set(subst(m, p.Index(i), pos))
- }
- return v
-
- case reflect.Struct:
- v := reflect.New(p.Type()).Elem()
- for i := 0; i < p.NumField(); i++ {
- v.Field(i).Set(subst(m, p.Field(i), pos))
- }
- return v
-
- case reflect.Ptr:
- v := reflect.New(p.Type()).Elem()
- if elem := p.Elem(); elem.IsValid() {
- v.Set(subst(m, elem, pos).Addr())
- }
- return v
-
- case reflect.Interface:
- v := reflect.New(p.Type()).Elem()
- if elem := p.Elem(); elem.IsValid() {
- v.Set(subst(m, elem, pos))
- }
- return v
- }
-
- return pattern
-}
projects / dotfiles / .git / blobdiff