src/go/types/generate_test.go - go - Git at Google

 // Copyright 2023 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.

 // This file implements a custom generator to create various go/types
 // source files from the corresponding types2 files.

 package types_test

 import (
 	"bytes"
 	"flag"
 	"fmt"
 	"go/ast"
 	"go/format"
 	"go/parser"
 	"go/token"
 	"internal/diff"
 	"os"
 	"path/filepath"
 	"runtime"
 	"strings"
 	"testing"
 )

 var filesToWrite = flag.String("write", "", `go/types files to generate, or "all" for all files`)

 const (
 	srcDir = "/src/cmd/compile/internal/types2/"
 	dstDir = "/src/go/types/"
 )

 // TestGenerate verifies that generated files in go/types match their types2
 // counterpart. If -write is set, this test actually writes the expected
 // content to go/types; otherwise, it just compares with the existing content.
 func TestGenerate(t *testing.T) {
 	// If filesToWrite is set, write the generated content to disk.
 	// In the special case of "all", write all files in filemap.
 	write := *filesToWrite != ""
 	var files []string // files to process
 	if *filesToWrite != "" && *filesToWrite != "all" {
 		files = strings.Split(*filesToWrite, ",")
 	} else {
 		for file := range filemap {
 			files = append(files, file)
 		}
 	}

 	for _, filename := range files {
 		generate(t, filename, write)
 	}
 }

 func generate(t *testing.T, filename string, write bool) {
 	// parse src (cmd/compile/internal/types2)
 	srcFilename := filepath.FromSlash(runtime.GOROOT() + srcDir + filename)
 	file, err := parser.ParseFile(fset, srcFilename, nil, parser.ParseComments)
 	if err != nil {
 		t.Fatal(err)
 	}

 	// fix package name
 	file.Name.Name = strings.ReplaceAll(file.Name.Name, "types2", "types")

 	// rewrite AST as needed
 	if action := filemap[filename]; action != nil {
 		action(file)
 	}

 	// format AST
 	var buf bytes.Buffer
 	rel, _ := filepath.Rel(dstDir, srcDir)
 	fmt.Fprintf(&buf, "// Code generated by \"go test -run=Generate -write=all\"; DO NOT EDIT.\n")
 	fmt.Fprintf(&buf, "// Source: %s/%s\n\n", filepath.ToSlash(rel), filename)
 	if err := format.Node(&buf, fset, file); err != nil {
 		t.Fatal(err)
 	}
 	generatedContent := buf.Bytes()

 	// read dst (go/types)
 	dstFilename := filepath.FromSlash(runtime.GOROOT() + dstDir + filename)
 	onDiskContent, err := os.ReadFile(dstFilename)
 	if err != nil {
 		t.Fatalf("reading %q: %v", filename, err)
 	}

 	// compare on-disk dst with buffer generated from src.
 	if d := diff.Diff(filename+" (on disk in "+dstDir+")", onDiskContent, filename+" (generated from "+srcDir+")", generatedContent); d != nil {
 		if write {
 			t.Logf("applying change:\n%s", d)
 			if err := os.WriteFile(dstFilename, generatedContent, 0o644); err != nil {
 				t.Fatalf("writing %q: %v", filename, err)
 			}
 		} else {
 			t.Errorf("file on disk in %s is stale:\n%s", dstDir, d)
 		}
 	}
 }

 type action func(in *ast.File)

 var filemap = map[string]action{
 	"alias.go": fixTokenPos,
 	"assignments.go": func(f *ast.File) {
 		renameImportPath(f, `"cmd/compile/internal/syntax"->"go/ast"`)
 		renameSelectorExprs(f, "syntax.Name->ast.Ident", "ident.Value->ident.Name", "ast.Pos->token.Pos") // must happen before renaming identifiers
 		renameIdents(f, "syntax->ast", "poser->positioner", "nopos->noposn")
 	},
 	"array.go":          nil,
 	"api_predicates.go": nil,
 	"basic.go":          nil,
 	"builtins.go": func(f *ast.File) {
 		renameImportPath(f, `"cmd/compile/internal/syntax"->"go/ast"`)
 		renameIdents(f, "syntax->ast")
 		renameSelectors(f, "ArgList->Args")
 		fixSelValue(f)
 		fixAtPosCall(f)
 	},
 	"builtins_test.go": func(f *ast.File) {
 		renameImportPath(f, `"cmd/compile/internal/syntax"->"go/ast"`, `"cmd/compile/internal/types2"->"go/types"`)
 		renameSelectorExprs(f, "syntax.Name->ast.Ident", "p.Value->p.Name") // must happen before renaming identifiers
 		renameIdents(f, "syntax->ast")
 	},
 	"chan.go":         nil,
 	"const.go":        fixTokenPos,
 	"context.go":      nil,
 	"context_test.go": nil,
 	"conversions.go":  nil,
 	"errors_test.go":  func(f *ast.File) { renameIdents(f, "nopos->noposn") },
 	"errsupport.go":   nil,
 	"gccgosizes.go":   nil,
 	"gcsizes.go":      func(f *ast.File) { renameIdents(f, "IsSyncAtomicAlign64->_IsSyncAtomicAlign64") },
 	"hilbert_test.go": func(f *ast.File) { renameImportPath(f, `"cmd/compile/internal/types2"->"go/types"`) },
 	"infer.go":        func(f *ast.File) { fixTokenPos(f); fixInferSig(f) },
 	"initorder.go":    nil,
 	// "initorder.go": fixErrErrorfCall, // disabled for now due to unresolved error_ use implications for gopls
 	"instantiate.go":      func(f *ast.File) { fixTokenPos(f); fixCheckErrorfCall(f) },
 	"instantiate_test.go": func(f *ast.File) { renameImportPath(f, `"cmd/compile/internal/types2"->"go/types"`) },
 	"literals.go": func(f *ast.File) {
 		insertImportPath(f, `"go/token"`)
 		renameImportPath(f, `"cmd/compile/internal/syntax"->"go/ast"`)
 		renameSelectorExprs(f,
 			"syntax.IntLit->token.INT", "syntax.FloatLit->token.FLOAT", "syntax.ImagLit->token.IMAG",
 			"syntax.Name->ast.Ident", "key.Value->key.Name", "atyp.Elem->atyp.Elt") // must happen before renaming identifiers
 		renameIdents(f, "syntax->ast")
 		renameSelectors(f, "ElemList->Elts")
 	},
 	"lookup.go":    func(f *ast.File) { fixTokenPos(f) },
 	"main_test.go": nil,
 	"map.go":       nil,
 	"mono.go": func(f *ast.File) {
 		fixTokenPos(f)
 		insertImportPath(f, `"go/ast"`)
 		renameSelectorExprs(f, "syntax.Expr->ast.Expr")
 	},
 	"named.go":  func(f *ast.File) { fixTokenPos(f); renameSelectors(f, "Trace->_Trace") },
 	"object.go": func(f *ast.File) { fixTokenPos(f); renameIdents(f, "NewTypeNameLazy->_NewTypeNameLazy") },
 	// TODO(gri) needs adjustments for TestObjectString - disabled for now
 	// "object_test.go": func(f *ast.File) { renameImportPath(f, `"cmd/compile/internal/types2"->"go/types"`) },
 	"objset.go": nil,
 	"operand.go": func(f *ast.File) {
 		insertImportPath(f, `"go/token"`)
 		renameImportPath(f, `"cmd/compile/internal/syntax"->"go/ast"`)
 		renameSelectorExprs(f,
 			"syntax.Pos->token.Pos", "syntax.LitKind->token.Token",
 			"syntax.IntLit->token.INT", "syntax.FloatLit->token.FLOAT",
 			"syntax.ImagLit->token.IMAG", "syntax.RuneLit->token.CHAR",
 			"syntax.StringLit->token.STRING") // must happen before renaming identifiers
 		renameIdents(f, "syntax->ast")
 	},
 	"package.go":    nil,
 	"pointer.go":    nil,
 	"predicates.go": nil,
 	"range.go": func(f *ast.File) {
 		renameImportPath(f, `"cmd/compile/internal/syntax"->"go/ast"`)
 		renameSelectorExprs(f, "syntax.Name->ast.Ident", "syntax.ForStmt->ast.RangeStmt", "ident.Value->ident.Name") // must happen before renaming identifiers
 		renameIdents(f, "syntax->ast", "poser->positioner")
 	},
 	"recording.go": func(f *ast.File) {
 		renameImportPath(f, `"cmd/compile/internal/syntax"->"go/ast"`)
 		renameSelectorExprs(f, "syntax.Name->ast.Ident") // must happen before renaming identifiers
 		renameIdents(f, "syntax->ast")
 		fixAtPosCall(f)
 	},
 	"scope.go":         func(f *ast.File) { fixTokenPos(f); renameIdents(f, "InsertLazy->_InsertLazy") },
 	"selection.go":     nil,
 	"sizes.go":         func(f *ast.File) { renameIdents(f, "IsSyncAtomicAlign64->_IsSyncAtomicAlign64") },
 	"slice.go":         nil,
 	"subst.go":         func(f *ast.File) { fixTokenPos(f); renameSelectors(f, "Trace->_Trace") },
 	"termlist.go":      nil,
 	"termlist_test.go": nil,
 	"tuple.go":         nil,
 	"typelists.go":     nil,
 	"typeset.go":       func(f *ast.File) { fixTokenPos(f); renameSelectors(f, "Trace->_Trace") },
 	"typeparam.go":     nil,
 	"typeterm_test.go": nil,
 	"typeterm.go":      nil,
 	"typestring.go":    nil,
 	"under.go":         nil,
 	"unify.go":         fixSprintf,
 	"universe.go":      fixGlobalTypVarDecl,
 	"util_test.go":     fixTokenPos,
 	"validtype.go":     func(f *ast.File) { fixTokenPos(f); renameSelectors(f, "Trace->_Trace") },
 }

 // TODO(gri) We should be able to make these rewriters more configurable/composable.
 //           For now this is a good starting point.

 // A renameMap maps old strings to new strings.
 type renameMap map[string]string

 // makeRenameMap returns a renameMap populates from renames entries of the form "from->to".
 func makeRenameMap(renames ...string) renameMap {
 	m := make(renameMap)
 	for _, r := range renames {
 		s := strings.Split(r, "->")
 		if len(s) != 2 {
 			panic("invalid rename entry: " + r)
 		}
 		m[s[0]] = s[1]
 	}
 	return m
 }

 // rename renames the given string s if a corresponding rename exists in m.
 func (m renameMap) rename(s *string) {
 	if r, ok := m[*s]; ok {
 		*s = r
 	}
 }

 // renameSel renames a selector expression of the form a.x to b.x (where a, b are identifiers)
 // if m contains the ("a.x" : "b.y") key-value pair.
 func (m renameMap) renameSel(n *ast.SelectorExpr) {
 	if a, _ := n.X.(*ast.Ident); a != nil {
 		a_x := a.Name + "." + n.Sel.Name
 		if r, ok := m[a_x]; ok {
 			b_y := strings.Split(r, ".")
 			if len(b_y) != 2 {
 				panic("invalid selector expression: " + r)
 			}
 			a.Name = b_y[0]
 			n.Sel.Name = b_y[1]
 		}
 	}
 }

 // renameIdents renames identifiers: each renames entry is of the form "from->to".
 // Note: This doesn't change the use of the identifiers in comments.
 func renameIdents(f *ast.File, renames ...string) {
 	m := makeRenameMap(renames...)
 	ast.Inspect(f, func(n ast.Node) bool {
 		switch n := n.(type) {
 		case *ast.Ident:
 			m.rename(&n.Name)
 			return false
 		}
 		return true
 	})
 }

 // renameSelectors is like renameIdents but only looks at selectors.
 func renameSelectors(f *ast.File, renames ...string) {
 	m := makeRenameMap(renames...)
 	ast.Inspect(f, func(n ast.Node) bool {
 		switch n := n.(type) {
 		case *ast.SelectorExpr:
 			m.rename(&n.Sel.Name)
 			return false
 		}
 		return true
 	})

 }

 // renameSelectorExprs is like renameIdents but only looks at selector expressions.
 // Each renames entry must be of the form "x.a->y.b".
 func renameSelectorExprs(f *ast.File, renames ...string) {
 	m := makeRenameMap(renames...)
 	ast.Inspect(f, func(n ast.Node) bool {
 		switch n := n.(type) {
 		case *ast.SelectorExpr:
 			m.renameSel(n)
 			return false
 		}
 		return true
 	})
 }

 // renameImportPath is like renameIdents but renames import paths.
 func renameImportPath(f *ast.File, renames ...string) {
 	m := makeRenameMap(renames...)
 	ast.Inspect(f, func(n ast.Node) bool {
 		switch n := n.(type) {
 		case *ast.ImportSpec:
 			if n.Path.Kind != token.STRING {
 				panic("invalid import path")
 			}
 			m.rename(&n.Path.Value)
 			return false
 		}
 		return true
 	})
 }

 // insertImportPath inserts the given import path.
 // There must be at least one import declaration present already.
 func insertImportPath(f *ast.File, path string) {
 	for _, d := range f.Decls {
 		if g, _ := d.(*ast.GenDecl); g != nil && g.Tok == token.IMPORT {
 			g.Specs = append(g.Specs, &ast.ImportSpec{Path: &ast.BasicLit{ValuePos: g.End(), Kind: token.STRING, Value: path}})
 			return
 		}
 	}
 	panic("no import declaration present")
 }

 // fixTokenPos changes imports of "cmd/compile/internal/syntax" to "go/token",
 // uses of syntax.Pos to token.Pos, and calls to x.IsKnown() to x.IsValid().
 func fixTokenPos(f *ast.File) {
 	m := makeRenameMap(`"cmd/compile/internal/syntax"->"go/token"`, "syntax.Pos->token.Pos", "IsKnown->IsValid")
 	ast.Inspect(f, func(n ast.Node) bool {
 		switch n := n.(type) {
 		case *ast.ImportSpec:
 			// rewrite import path "cmd/compile/internal/syntax" to "go/token"
 			if n.Path.Kind != token.STRING {
 				panic("invalid import path")
 			}
 			m.rename(&n.Path.Value)
 			return false
 		case *ast.SelectorExpr:
 			// rewrite syntax.Pos to token.Pos
 			m.renameSel(n)
 		case *ast.CallExpr:
 			// rewrite x.IsKnown() to x.IsValid()
 			if fun, _ := n.Fun.(*ast.SelectorExpr); fun != nil && len(n.Args) == 0 {
 				m.rename(&fun.Sel.Name)
 				return false
 			}
 		}
 		return true
 	})
 }

 // fixSelValue updates the selector x.Sel.Value to x.Sel.Name.
 func fixSelValue(f *ast.File) {
 	ast.Inspect(f, func(n ast.Node) bool {
 		switch n := n.(type) {
 		case *ast.SelectorExpr:
 			if n.Sel.Name == "Value" {
 				if selx, _ := n.X.(*ast.SelectorExpr); selx != nil && selx.Sel.Name == "Sel" {
 					n.Sel.Name = "Name"
 					return false
 				}
 			}
 		}
 		return true
 	})
 }

 // fixInferSig updates the Checker.infer signature to use a positioner instead of a token.Position
 // as first argument, renames the argument from "pos" to "posn", and updates a few internal uses of
 // "pos" to "posn" and "posn.Pos()" respectively.
 func fixInferSig(f *ast.File) {
 	ast.Inspect(f, func(n ast.Node) bool {
 		switch n := n.(type) {
 		case *ast.FuncDecl:
 			if n.Name.Name == "infer" {
 				// rewrite (pos token.Pos, ...) to (posn positioner, ...)
 				par := n.Type.Params.List[0]
 				if len(par.Names) == 1 && par.Names[0].Name == "pos" {
 					par.Names[0] = newIdent(par.Names[0].Pos(), "posn")
 					par.Type = newIdent(par.Type.Pos(), "positioner")
 					return true
 				}
 			}
 		case *ast.CallExpr:
 			if selx, _ := n.Fun.(*ast.SelectorExpr); selx != nil {
 				switch selx.Sel.Name {
 				case "renameTParams":
 					// rewrite check.renameTParams(pos, ... ) to check.renameTParams(posn.Pos(), ... )
 					if isIdent(n.Args[0], "pos") {
 						pos := n.Args[0].Pos()
 						fun := &ast.SelectorExpr{X: newIdent(pos, "posn"), Sel: newIdent(pos, "Pos")}
 						arg := &ast.CallExpr{Fun: fun, Lparen: pos, Args: nil, Ellipsis: token.NoPos, Rparen: pos}
 						n.Args[0] = arg
 						return false
 					}
 				case "addf":
 					// rewrite err.addf(pos, ...) to err.addf(posn, ...)
 					if isIdent(n.Args[0], "pos") {
 						pos := n.Args[0].Pos()
 						arg := newIdent(pos, "posn")
 						n.Args[0] = arg
 						return false
 					}
 				case "allowVersion":
 					// rewrite check.allowVersion(pos, ...) to check.allowVersion(posn, ...)
 					if isIdent(n.Args[0], "pos") {
 						pos := n.Args[0].Pos()
 						arg := newIdent(pos, "posn")
 						n.Args[0] = arg
 						return false
 					}
 				}
 			}
 		}
 		return true
 	})
 }

 // fixAtPosCall updates calls of the form atPos(x) to x.Pos() in argument lists of (check).dump calls.
 // TODO(gri) can we avoid this and just use atPos consistently in go/types and types2?
 func fixAtPosCall(f *ast.File) {
 	ast.Inspect(f, func(n ast.Node) bool {
 		switch n := n.(type) {
 		case *ast.CallExpr:
 			if selx, _ := n.Fun.(*ast.SelectorExpr); selx != nil && selx.Sel.Name == "dump" {
 				for i, arg := range n.Args {
 					if call, _ := arg.(*ast.CallExpr); call != nil {
 						// rewrite xxx.dump(..., atPos(x), ...) to xxx.dump(..., x.Pos(), ...)
 						if isIdent(call.Fun, "atPos") {
 							pos := call.Args[0].Pos()
 							fun := &ast.SelectorExpr{X: call.Args[0], Sel: newIdent(pos, "Pos")}
 							n.Args[i] = &ast.CallExpr{Fun: fun, Lparen: pos, Rparen: pos}
 							return false
 						}
 					}
 				}
 			}
 		}
 		return true
 	})
 }

 // fixErrErrorfCall updates calls of the form err.addf(obj, ...) to err.addf(obj.Pos(), ...).
 func fixErrErrorfCall(f *ast.File) {
 	ast.Inspect(f, func(n ast.Node) bool {
 		switch n := n.(type) {
 		case *ast.CallExpr:
 			if selx, _ := n.Fun.(*ast.SelectorExpr); selx != nil {
 				if isIdent(selx.X, "err") {
 					switch selx.Sel.Name {
 					case "errorf":
 						// rewrite err.addf(obj, ... ) to err.addf(obj.Pos(), ... )
 						if ident, _ := n.Args[0].(*ast.Ident); ident != nil && ident.Name == "obj" {
 							pos := n.Args[0].Pos()
 							fun := &ast.SelectorExpr{X: ident, Sel: newIdent(pos, "Pos")}
 							n.Args[0] = &ast.CallExpr{Fun: fun, Lparen: pos, Rparen: pos}
 							return false
 						}
 					}
 				}
 			}
 		}
 		return true
 	})
 }

 // fixCheckErrorfCall updates calls of the form check.errorf(pos, ...) to check.errorf(atPos(pos), ...).
 func fixCheckErrorfCall(f *ast.File) {
 	ast.Inspect(f, func(n ast.Node) bool {
 		switch n := n.(type) {
 		case *ast.CallExpr:
 			if selx, _ := n.Fun.(*ast.SelectorExpr); selx != nil {
 				if isIdent(selx.X, "check") {
 					switch selx.Sel.Name {
 					case "errorf":
 						// rewrite check.errorf(pos, ... ) to check.errorf(atPos(pos), ... )
 						if ident := asIdent(n.Args[0], "pos"); ident != nil {
 							pos := n.Args[0].Pos()
 							fun := newIdent(pos, "atPos")
 							n.Args[0] = &ast.CallExpr{Fun: fun, Lparen: pos, Args: []ast.Expr{ident}, Rparen: pos}
 							return false
 						}
 					}
 				}
 			}
 		}
 		return true
 	})
 }

 // fixGlobalTypVarDecl changes the global Typ variable from an array to a slice
 // (in types2 we use an array for efficiency, in go/types it's a slice and we
 // cannot change that).
 func fixGlobalTypVarDecl(f *ast.File) {
 	ast.Inspect(f, func(n ast.Node) bool {
 		switch n := n.(type) {
 		case *ast.ValueSpec:
 			// rewrite type Typ = [...]Type{...} to type Typ = []Type{...}
 			if len(n.Names) == 1 && n.Names[0].Name == "Typ" && len(n.Values) == 1 {
 				n.Values[0].(*ast.CompositeLit).Type.(*ast.ArrayType).Len = nil
 				return false
 			}
 		}
 		return true
 	})
 }

 // fixSprintf adds an extra nil argument for the *token.FileSet parameter in sprintf calls.
 func fixSprintf(f *ast.File) {
 	ast.Inspect(f, func(n ast.Node) bool {
 		switch n := n.(type) {
 		case *ast.CallExpr:
 			if isIdent(n.Fun, "sprintf") && len(n.Args) >= 4 /* ... args */ {
 				n.Args = insert(n.Args, 1, newIdent(n.Args[1].Pos(), "nil"))
 				return false
 			}
 		}
 		return true
 	})
 }

 // asIdent returns x as *ast.Ident if it is an identifier with the given name.
 func asIdent(x ast.Node, name string) *ast.Ident {
 	if ident, _ := x.(*ast.Ident); ident != nil && ident.Name == name {
 		return ident
 	}
 	return nil
 }

 // isIdent reports whether x is an identifier with the given name.
 func isIdent(x ast.Node, name string) bool {
 	return asIdent(x, name) != nil
 }

 // newIdent returns a new identifier with the given position and name.
 func newIdent(pos token.Pos, name string) *ast.Ident {
 	id := ast.NewIdent(name)
 	id.NamePos = pos
 	return id
 }

 // insert inserts x at list[at] and moves the remaining elements up.
 func insert(list []ast.Expr, at int, x ast.Expr) []ast.Expr {
 	list = append(list, nil)
 	copy(list[at+1:], list[at:])
 	list[at] = x
 	return list
 }
	// Copyright 2023 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.

	// This file implements a custom generator to create various go/types
	// source files from the corresponding types2 files.

	package types_test

	import (
	"bytes"
	"flag"
	"fmt"
	"go/ast"
	"go/format"
	"go/parser"
	"go/token"
	"internal/diff"
	"os"
	"path/filepath"
	"runtime"
	"strings"
	"testing"
	)

	var filesToWrite = flag.String("write", "", `go/types files to generate, or "all" for all files`)

	const (
	srcDir = "/src/cmd/compile/internal/types2/"
	dstDir = "/src/go/types/"
	)

	// TestGenerate verifies that generated files in go/types match their types2
	// counterpart. If -write is set, this test actually writes the expected
	// content to go/types; otherwise, it just compares with the existing content.
	func TestGenerate(t *testing.T) {
	// If filesToWrite is set, write the generated content to disk.
	// In the special case of "all", write all files in filemap.
	write := *filesToWrite != ""
	var files []string // files to process
	if filesToWrite != "" && filesToWrite != "all" {
	files = strings.Split(*filesToWrite, ",")
	} else {
	for file := range filemap {
	files = append(files, file)
	}
	}

	for _, filename := range files {
	generate(t, filename, write)
	}
	}

	func generate(t *testing.T, filename string, write bool) {
	// parse src (cmd/compile/internal/types2)
	srcFilename := filepath.FromSlash(runtime.GOROOT() + srcDir + filename)
	file, err := parser.ParseFile(fset, srcFilename, nil, parser.ParseComments)
	if err != nil {
	t.Fatal(err)
	}

	// fix package name
	file.Name.Name = strings.ReplaceAll(file.Name.Name, "types2", "types")

	// rewrite AST as needed
	if action := filemap[filename]; action != nil {
	action(file)
	}

	// format AST
	var buf bytes.Buffer
	rel, _ := filepath.Rel(dstDir, srcDir)
	fmt.Fprintf(&buf, "// Code generated by \"go test -run=Generate -write=all\"; DO NOT EDIT.\n")
	fmt.Fprintf(&buf, "// Source: %s/%s\n\n", filepath.ToSlash(rel), filename)
	if err := format.Node(&buf, fset, file); err != nil {
	t.Fatal(err)
	}
	generatedContent := buf.Bytes()

	// read dst (go/types)
	dstFilename := filepath.FromSlash(runtime.GOROOT() + dstDir + filename)
	onDiskContent, err := os.ReadFile(dstFilename)
	if err != nil {
	t.Fatalf("reading %q: %v", filename, err)
	}

	// compare on-disk dst with buffer generated from src.
	if d := diff.Diff(filename+" (on disk in "+dstDir+")", onDiskContent, filename+" (generated from "+srcDir+")", generatedContent); d != nil {
	if write {
	t.Logf("applying change:\n%s", d)
	if err := os.WriteFile(dstFilename, generatedContent, 0o644); err != nil {
	t.Fatalf("writing %q: %v", filename, err)
	}
	} else {
	t.Errorf("file on disk in %s is stale:\n%s", dstDir, d)
	}
	}
	}

	type action func(in *ast.File)

	var filemap = map[string]action{
	"alias.go": fixTokenPos,
	"assignments.go": func(f *ast.File) {
	renameImportPath(f, `"cmd/compile/internal/syntax"->"go/ast"`)
	renameSelectorExprs(f, "syntax.Name->ast.Ident", "ident.Value->ident.Name", "ast.Pos->token.Pos") // must happen before renaming identifiers
	renameIdents(f, "syntax->ast", "poser->positioner", "nopos->noposn")
	},
	"array.go": nil,
	"api_predicates.go": nil,
	"basic.go": nil,
	"builtins.go": func(f *ast.File) {
	renameImportPath(f, `"cmd/compile/internal/syntax"->"go/ast"`)
	renameIdents(f, "syntax->ast")
	renameSelectors(f, "ArgList->Args")
	fixSelValue(f)
	fixAtPosCall(f)
	},
	"builtins_test.go": func(f *ast.File) {
	renameImportPath(f, `"cmd/compile/internal/syntax"->"go/ast"`, `"cmd/compile/internal/types2"->"go/types"`)
	renameSelectorExprs(f, "syntax.Name->ast.Ident", "p.Value->p.Name") // must happen before renaming identifiers
	renameIdents(f, "syntax->ast")
	},
	"chan.go": nil,
	"const.go": fixTokenPos,
	"context.go": nil,
	"context_test.go": nil,
	"conversions.go": nil,
	"errors_test.go": func(f *ast.File) { renameIdents(f, "nopos->noposn") },
	"errsupport.go": nil,
	"gccgosizes.go": nil,
	"gcsizes.go": func(f *ast.File) { renameIdents(f, "IsSyncAtomicAlign64->_IsSyncAtomicAlign64") },
	"hilbert_test.go": func(f *ast.File) { renameImportPath(f, `"cmd/compile/internal/types2"->"go/types"`) },
	"infer.go": func(f *ast.File) { fixTokenPos(f); fixInferSig(f) },
	"initorder.go": nil,
	// "initorder.go": fixErrErrorfCall, // disabled for now due to unresolved error_ use implications for gopls
	"instantiate.go": func(f *ast.File) { fixTokenPos(f); fixCheckErrorfCall(f) },
	"instantiate_test.go": func(f *ast.File) { renameImportPath(f, `"cmd/compile/internal/types2"->"go/types"`) },
	"literals.go": func(f *ast.File) {
	insertImportPath(f, `"go/token"`)
	renameImportPath(f, `"cmd/compile/internal/syntax"->"go/ast"`)
	renameSelectorExprs(f,
	"syntax.IntLit->token.INT", "syntax.FloatLit->token.FLOAT", "syntax.ImagLit->token.IMAG",
	"syntax.Name->ast.Ident", "key.Value->key.Name", "atyp.Elem->atyp.Elt") // must happen before renaming identifiers
	renameIdents(f, "syntax->ast")
	renameSelectors(f, "ElemList->Elts")
	},
	"lookup.go": func(f *ast.File) { fixTokenPos(f) },
	"main_test.go": nil,
	"map.go": nil,
	"mono.go": func(f *ast.File) {
	fixTokenPos(f)
	insertImportPath(f, `"go/ast"`)
	renameSelectorExprs(f, "syntax.Expr->ast.Expr")
	},
	"named.go": func(f *ast.File) { fixTokenPos(f); renameSelectors(f, "Trace->_Trace") },
	"object.go": func(f *ast.File) { fixTokenPos(f); renameIdents(f, "NewTypeNameLazy->_NewTypeNameLazy") },
	// TODO(gri) needs adjustments for TestObjectString - disabled for now
	// "object_test.go": func(f *ast.File) { renameImportPath(f, `"cmd/compile/internal/types2"->"go/types"`) },
	"objset.go": nil,
	"operand.go": func(f *ast.File) {
	insertImportPath(f, `"go/token"`)
	renameImportPath(f, `"cmd/compile/internal/syntax"->"go/ast"`)
	renameSelectorExprs(f,
	"syntax.Pos->token.Pos", "syntax.LitKind->token.Token",
	"syntax.IntLit->token.INT", "syntax.FloatLit->token.FLOAT",
	"syntax.ImagLit->token.IMAG", "syntax.RuneLit->token.CHAR",
	"syntax.StringLit->token.STRING") // must happen before renaming identifiers
	renameIdents(f, "syntax->ast")
	},
	"package.go": nil,
	"pointer.go": nil,
	"predicates.go": nil,
	"range.go": func(f *ast.File) {
	renameImportPath(f, `"cmd/compile/internal/syntax"->"go/ast"`)
	renameSelectorExprs(f, "syntax.Name->ast.Ident", "syntax.ForStmt->ast.RangeStmt", "ident.Value->ident.Name") // must happen before renaming identifiers
	renameIdents(f, "syntax->ast", "poser->positioner")
	},
	"recording.go": func(f *ast.File) {
	renameImportPath(f, `"cmd/compile/internal/syntax"->"go/ast"`)
	renameSelectorExprs(f, "syntax.Name->ast.Ident") // must happen before renaming identifiers
	renameIdents(f, "syntax->ast")
	fixAtPosCall(f)
	},
	"scope.go": func(f *ast.File) { fixTokenPos(f); renameIdents(f, "InsertLazy->_InsertLazy") },
	"selection.go": nil,
	"sizes.go": func(f *ast.File) { renameIdents(f, "IsSyncAtomicAlign64->_IsSyncAtomicAlign64") },
	"slice.go": nil,
	"subst.go": func(f *ast.File) { fixTokenPos(f); renameSelectors(f, "Trace->_Trace") },
	"termlist.go": nil,
	"termlist_test.go": nil,
	"tuple.go": nil,
	"typelists.go": nil,
	"typeset.go": func(f *ast.File) { fixTokenPos(f); renameSelectors(f, "Trace->_Trace") },
	"typeparam.go": nil,
	"typeterm_test.go": nil,
	"typeterm.go": nil,
	"typestring.go": nil,
	"under.go": nil,
	"unify.go": fixSprintf,
	"universe.go": fixGlobalTypVarDecl,
	"util_test.go": fixTokenPos,
	"validtype.go": func(f *ast.File) { fixTokenPos(f); renameSelectors(f, "Trace->_Trace") },
	}

	// TODO(gri) We should be able to make these rewriters more configurable/composable.
	// For now this is a good starting point.

	// A renameMap maps old strings to new strings.
	type renameMap map[string]string

	// makeRenameMap returns a renameMap populates from renames entries of the form "from->to".
	func makeRenameMap(renames ...string) renameMap {
	m := make(renameMap)
	for _, r := range renames {
	s := strings.Split(r, "->")
	if len(s) != 2 {
	panic("invalid rename entry: " + r)
	}
	m[s[0]] = s[1]
	}
	return m
	}

	// rename renames the given string s if a corresponding rename exists in m.
	func (m renameMap) rename(s *string) {
	if r, ok := m[*s]; ok {
	*s = r
	}
	}

	// renameSel renames a selector expression of the form a.x to b.x (where a, b are identifiers)
	// if m contains the ("a.x" : "b.y") key-value pair.
	func (m renameMap) renameSel(n *ast.SelectorExpr) {
	if a, _ := n.X.(*ast.Ident); a != nil {
	a_x := a.Name + "." + n.Sel.Name
	if r, ok := m[a_x]; ok {
	b_y := strings.Split(r, ".")
	if len(b_y) != 2 {
	panic("invalid selector expression: " + r)
	}
	a.Name = b_y[0]
	n.Sel.Name = b_y[1]
	}
	}
	}

	// renameIdents renames identifiers: each renames entry is of the form "from->to".
	// Note: This doesn't change the use of the identifiers in comments.
	func renameIdents(f *ast.File, renames ...string) {
	m := makeRenameMap(renames...)
	ast.Inspect(f, func(n ast.Node) bool {
	switch n := n.(type) {
	case *ast.Ident:
	m.rename(&n.Name)
	return false
	}
	return true
	})
	}

	// renameSelectors is like renameIdents but only looks at selectors.
	func renameSelectors(f *ast.File, renames ...string) {
	m := makeRenameMap(renames...)
	ast.Inspect(f, func(n ast.Node) bool {
	switch n := n.(type) {
	case *ast.SelectorExpr:
	m.rename(&n.Sel.Name)
	return false
	}
	return true
	})

	}

	// renameSelectorExprs is like renameIdents but only looks at selector expressions.
	// Each renames entry must be of the form "x.a->y.b".
	func renameSelectorExprs(f *ast.File, renames ...string) {
	m := makeRenameMap(renames...)
	ast.Inspect(f, func(n ast.Node) bool {
	switch n := n.(type) {
	case *ast.SelectorExpr:
	m.renameSel(n)
	return false
	}
	return true
	})
	}

	// renameImportPath is like renameIdents but renames import paths.
	func renameImportPath(f *ast.File, renames ...string) {
	m := makeRenameMap(renames...)
	ast.Inspect(f, func(n ast.Node) bool {
	switch n := n.(type) {
	case *ast.ImportSpec:
	if n.Path.Kind != token.STRING {
	panic("invalid import path")
	}
	m.rename(&n.Path.Value)
	return false
	}
	return true
	})
	}

	// insertImportPath inserts the given import path.
	// There must be at least one import declaration present already.
	func insertImportPath(f *ast.File, path string) {
	for _, d := range f.Decls {
	if g, _ := d.(*ast.GenDecl); g != nil && g.Tok == token.IMPORT {
	g.Specs = append(g.Specs, &ast.ImportSpec{Path: &ast.BasicLit{ValuePos: g.End(), Kind: token.STRING, Value: path}})
	return
	}
	}
	panic("no import declaration present")
	}

	// fixTokenPos changes imports of "cmd/compile/internal/syntax" to "go/token",
	// uses of syntax.Pos to token.Pos, and calls to x.IsKnown() to x.IsValid().
	func fixTokenPos(f *ast.File) {
	m := makeRenameMap(`"cmd/compile/internal/syntax"->"go/token"`, "syntax.Pos->token.Pos", "IsKnown->IsValid")
	ast.Inspect(f, func(n ast.Node) bool {
	switch n := n.(type) {
	case *ast.ImportSpec:
	// rewrite import path "cmd/compile/internal/syntax" to "go/token"
	if n.Path.Kind != token.STRING {
	panic("invalid import path")
	}
	m.rename(&n.Path.Value)
	return false
	case *ast.SelectorExpr:
	// rewrite syntax.Pos to token.Pos
	m.renameSel(n)
	case *ast.CallExpr:
	// rewrite x.IsKnown() to x.IsValid()
	if fun, _ := n.Fun.(*ast.SelectorExpr); fun != nil && len(n.Args) == 0 {
	m.rename(&fun.Sel.Name)
	return false
	}
	}
	return true
	})
	}

	// fixSelValue updates the selector x.Sel.Value to x.Sel.Name.
	func fixSelValue(f *ast.File) {
	ast.Inspect(f, func(n ast.Node) bool {
	switch n := n.(type) {
	case *ast.SelectorExpr:
	if n.Sel.Name == "Value" {
	if selx, _ := n.X.(*ast.SelectorExpr); selx != nil && selx.Sel.Name == "Sel" {
	n.Sel.Name = "Name"
	return false
	}
	}
	}
	return true
	})
	}

	// fixInferSig updates the Checker.infer signature to use a positioner instead of a token.Position
	// as first argument, renames the argument from "pos" to "posn", and updates a few internal uses of
	// "pos" to "posn" and "posn.Pos()" respectively.
	func fixInferSig(f *ast.File) {
	ast.Inspect(f, func(n ast.Node) bool {
	switch n := n.(type) {
	case *ast.FuncDecl:
	if n.Name.Name == "infer" {
	// rewrite (pos token.Pos, ...) to (posn positioner, ...)
	par := n.Type.Params.List[0]
	if len(par.Names) == 1 && par.Names[0].Name == "pos" {
	par.Names[0] = newIdent(par.Names[0].Pos(), "posn")
	par.Type = newIdent(par.Type.Pos(), "positioner")
	return true
	}
	}
	case *ast.CallExpr:
	if selx, _ := n.Fun.(*ast.SelectorExpr); selx != nil {
	switch selx.Sel.Name {
	case "renameTParams":
	// rewrite check.renameTParams(pos, ... ) to check.renameTParams(posn.Pos(), ... )
	if isIdent(n.Args[0], "pos") {
	pos := n.Args[0].Pos()
	fun := &ast.SelectorExpr{X: newIdent(pos, "posn"), Sel: newIdent(pos, "Pos")}
	arg := &ast.CallExpr{Fun: fun, Lparen: pos, Args: nil, Ellipsis: token.NoPos, Rparen: pos}
	n.Args[0] = arg
	return false
	}
	case "addf":
	// rewrite err.addf(pos, ...) to err.addf(posn, ...)
	if isIdent(n.Args[0], "pos") {
	pos := n.Args[0].Pos()
	arg := newIdent(pos, "posn")
	n.Args[0] = arg
	return false
	}
	case "allowVersion":
	// rewrite check.allowVersion(pos, ...) to check.allowVersion(posn, ...)
	if isIdent(n.Args[0], "pos") {
	pos := n.Args[0].Pos()
	arg := newIdent(pos, "posn")
	n.Args[0] = arg
	return false
	}
	}
	}
	}
	return true
	})
	}

	// fixAtPosCall updates calls of the form atPos(x) to x.Pos() in argument lists of (check).dump calls.
	// TODO(gri) can we avoid this and just use atPos consistently in go/types and types2?
	func fixAtPosCall(f *ast.File) {
	ast.Inspect(f, func(n ast.Node) bool {
	switch n := n.(type) {
	case *ast.CallExpr:
	if selx, _ := n.Fun.(*ast.SelectorExpr); selx != nil && selx.Sel.Name == "dump" {
	for i, arg := range n.Args {
	if call, _ := arg.(*ast.CallExpr); call != nil {
	// rewrite xxx.dump(..., atPos(x), ...) to xxx.dump(..., x.Pos(), ...)
	if isIdent(call.Fun, "atPos") {
	pos := call.Args[0].Pos()
	fun := &ast.SelectorExpr{X: call.Args[0], Sel: newIdent(pos, "Pos")}
	n.Args[i] = &ast.CallExpr{Fun: fun, Lparen: pos, Rparen: pos}
	return false
	}
	}
	}
	}
	}
	return true
	})
	}

	// fixErrErrorfCall updates calls of the form err.addf(obj, ...) to err.addf(obj.Pos(), ...).
	func fixErrErrorfCall(f *ast.File) {
	ast.Inspect(f, func(n ast.Node) bool {
	switch n := n.(type) {
	case *ast.CallExpr:
	if selx, _ := n.Fun.(*ast.SelectorExpr); selx != nil {
	if isIdent(selx.X, "err") {
	switch selx.Sel.Name {
	case "errorf":
	// rewrite err.addf(obj, ... ) to err.addf(obj.Pos(), ... )
	if ident, _ := n.Args[0].(*ast.Ident); ident != nil && ident.Name == "obj" {
	pos := n.Args[0].Pos()
	fun := &ast.SelectorExpr{X: ident, Sel: newIdent(pos, "Pos")}
	n.Args[0] = &ast.CallExpr{Fun: fun, Lparen: pos, Rparen: pos}
	return false
	}
	}
	}
	}
	}
	return true
	})
	}

	// fixCheckErrorfCall updates calls of the form check.errorf(pos, ...) to check.errorf(atPos(pos), ...).
	func fixCheckErrorfCall(f *ast.File) {
	ast.Inspect(f, func(n ast.Node) bool {
	switch n := n.(type) {
	case *ast.CallExpr:
	if selx, _ := n.Fun.(*ast.SelectorExpr); selx != nil {
	if isIdent(selx.X, "check") {
	switch selx.Sel.Name {
	case "errorf":
	// rewrite check.errorf(pos, ... ) to check.errorf(atPos(pos), ... )
	if ident := asIdent(n.Args[0], "pos"); ident != nil {
	pos := n.Args[0].Pos()
	fun := newIdent(pos, "atPos")
	n.Args[0] = &ast.CallExpr{Fun: fun, Lparen: pos, Args: []ast.Expr{ident}, Rparen: pos}
	return false
	}
	}
	}
	}
	}
	return true
	})
	}

	// fixGlobalTypVarDecl changes the global Typ variable from an array to a slice
	// (in types2 we use an array for efficiency, in go/types it's a slice and we
	// cannot change that).
	func fixGlobalTypVarDecl(f *ast.File) {
	ast.Inspect(f, func(n ast.Node) bool {
	switch n := n.(type) {
	case *ast.ValueSpec:
	// rewrite type Typ = [...]Type{...} to type Typ = []Type{...}
	if len(n.Names) == 1 && n.Names[0].Name == "Typ" && len(n.Values) == 1 {
	n.Values[0].(ast.CompositeLit).Type.(ast.ArrayType).Len = nil
	return false
	}
	}
	return true
	})
	}

	// fixSprintf adds an extra nil argument for the *token.FileSet parameter in sprintf calls.
	func fixSprintf(f *ast.File) {
	ast.Inspect(f, func(n ast.Node) bool {
	switch n := n.(type) {
	case *ast.CallExpr:
	if isIdent(n.Fun, "sprintf") && len(n.Args) >= 4 /* ... args */ {
	n.Args = insert(n.Args, 1, newIdent(n.Args[1].Pos(), "nil"))
	return false
	}
	}
	return true
	})
	}

	// asIdent returns x as *ast.Ident if it is an identifier with the given name.
	func asIdent(x ast.Node, name string) *ast.Ident {
	if ident, _ := x.(*ast.Ident); ident != nil && ident.Name == name {
	return ident
	}
	return nil
	}

	// isIdent reports whether x is an identifier with the given name.
	func isIdent(x ast.Node, name string) bool {
	return asIdent(x, name) != nil
	}

	// newIdent returns a new identifier with the given position and name.
	func newIdent(pos token.Pos, name string) *ast.Ident {
	id := ast.NewIdent(name)
	id.NamePos = pos
	return id
	}

	// insert inserts x at list[at] and moves the remaining elements up.
	func insert(list []ast.Expr, at int, x ast.Expr) []ast.Expr {
	list = append(list, nil)
	copy(list[at+1:], list[at:])
	list[at] = x
	return list
	}