diff --git a/format/format.go b/format/format.go
index aaae194..7316eb7 100644
--- a/format/format.go
+++ b/format/format.go
@@ -106,7 +106,7 @@ func File(fset *token.FileSet, file *ast.File, opts Options) {
 	}
 	opts.LangVersion = "v" + m[2] + "." + m[3]
 	f := &fumpter{
-		File:    fset.File(file.Pos()),
+		file:    fset.File(file.Pos()),
 		fset:    fset,
 		astFile: file,
 		Options: opts,
@@ -179,7 +179,7 @@ var rxOctalInteger = regexp.MustCompile(`\A0[0-7_]+\z`)
 type fumpter struct {
 	Options
 
-	*token.File
+	file *token.File
 	fset *token.FileSet
 
 	astFile *ast.File
@@ -227,7 +227,7 @@ func (f *fumpter) addNewline(at token.Pos) {
 	offset := f.Offset(at)
 
 	// TODO: replace with the new Lines method once we require Go 1.21 or later
-	field := reflect.ValueOf(f.File).Elem().FieldByName("lines")
+	field := reflect.ValueOf(f.file).Elem().FieldByName("lines")
 	n := field.Len()
 	lines := make([]int, 0, n+1)
 	for i := 0; i < n; i++ {
@@ -246,7 +246,7 @@ func (f *fumpter) addNewline(at token.Pos) {
 	if offset >= 0 {
 		lines = append(lines, offset)
 	}
-	if !f.SetLines(lines) {
+	if !f.file.SetLines(lines) {
 		panic(fmt.Sprintf("could not set lines to %v", lines))
 	}
 }
@@ -255,7 +255,7 @@ func (f *fumpter) addNewline(at token.Pos) {
 // up on the same line.
 func (f *fumpter) removeLines(fromLine, toLine int) {
 	for fromLine < toLine {
-		f.MergeLine(fromLine)
+		f.file.MergeLine(fromLine)
 		toLine--
 	}
 }
@@ -266,6 +266,18 @@ func (f *fumpter) removeLinesBetween(from, to token.Pos) {
 	f.removeLines(f.Line(from)+1, f.Line(to))
 }
 
+func (f *fumpter) Position(p token.Pos) token.Position {
+	return f.file.PositionFor(p, false)
+}
+
+func (f *fumpter) Line(p token.Pos) int {
+	return f.Position(p).Line
+}
+
+func (f *fumpter) Offset(p token.Pos) int {
+	return f.file.Offset(p)
+}
+
 type byteCounter int
 
 func (b *byteCounter) Write(p []byte) (n int, err error) {
@@ -295,14 +307,14 @@ func (f *fumpter) lineEnd(line int) token.Pos {
 	if line < 1 {
 		panic("illegal line number")
 	}
-	total := f.LineCount()
+	total := f.file.LineCount()
 	if line > total {
 		panic("illegal line number")
 	}
 	if line == total {
 		return f.astFile.End()
 	}
-	return f.LineStart(line+1) - 1
+	return f.file.LineStart(line+1) - 1
 }
 
 // rxCommentDirective covers all common Go comment directives:
diff --git a/testdata/script/linedirectives.txtar b/testdata/script/linedirectives.txtar
new file mode 100644
index 0000000..91f4291
--- /dev/null
+++ b/testdata/script/linedirectives.txtar
@@ -0,0 +1,173 @@
+# Line directives can throw off our use of MergeLines.
+# We should ignore them entirely when calculating line numbers.
+# The file below is borrowed from Go's test/dwarf/linedirectives.go.
+
+exec gofumpt -w foo.go
+cmp foo.go foo.go.golden
+
+-- foo.go --
+// Copyright 2011 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.
+
+//line foo/bar.y:4
+package main
+//line foo/bar.y:60
+func main() { 
+//line foo/bar.y:297
+	f, l := 0, 0
+//line yacctab:1
+	f, l = 1, 1
+//line yaccpar:1
+	f, l = 2, 1
+//line foo/bar.y:82
+	f, l = 3, 82
+//line foo/bar.y:90
+	f, l = 3, 90
+//line foo/bar.y:92
+	f, l = 3, 92
+//line foo/bar.y:100
+	f, l = 3, 100
+//line foo/bar.y:104
+	l = 104
+//line foo/bar.y:112
+	l = 112
+//line foo/bar.y:117
+	l = 117
+//line foo/bar.y:121
+	l = 121
+//line foo/bar.y:125
+	l = 125
+//line foo/bar.y:133
+	l = 133
+//line foo/bar.y:146
+	l = 146
+//line foo/bar.y:148
+//line foo/bar.y:153
+//line foo/bar.y:155
+	l = 155
+//line foo/bar.y:160
+
+//line foo/bar.y:164
+//line foo/bar.y:173
+
+//line foo/bar.y:178
+//line foo/bar.y:180
+//line foo/bar.y:185
+//line foo/bar.y:195
+//line foo/bar.y:197
+//line foo/bar.y:202
+//line foo/bar.y:204
+//line foo/bar.y:208
+//line foo/bar.y:211
+//line foo/bar.y:213
+//line foo/bar.y:215
+//line foo/bar.y:217
+//line foo/bar.y:221
+//line foo/bar.y:229
+//line foo/bar.y:236
+//line foo/bar.y:238
+//line foo/bar.y:240
+//line foo/bar.y:244
+//line foo/bar.y:249
+//line foo/bar.y:253
+//line foo/bar.y:257
+//line foo/bar.y:262
+//line foo/bar.y:267
+//line foo/bar.y:272
+	if l == f {
+//line foo/bar.y:277
+	panic("aie!")
+//line foo/bar.y:281
+	}
+//line foo/bar.y:285
+	return
+//line foo/bar.y:288
+//line foo/bar.y:290
+}
+//line foo/bar.y:293
+//line foo/bar.y:295
+-- foo.go.golden --
+// Copyright 2011 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.
+
+//line foo/bar.y:4
+package main
+
+//line foo/bar.y:60
+func main() {
+//line foo/bar.y:297
+	f, l := 0, 0
+//line yacctab:1
+	f, l = 1, 1
+//line yaccpar:1
+	f, l = 2, 1
+//line foo/bar.y:82
+	f, l = 3, 82
+//line foo/bar.y:90
+	f, l = 3, 90
+//line foo/bar.y:92
+	f, l = 3, 92
+//line foo/bar.y:100
+	f, l = 3, 100
+//line foo/bar.y:104
+	l = 104
+//line foo/bar.y:112
+	l = 112
+//line foo/bar.y:117
+	l = 117
+//line foo/bar.y:121
+	l = 121
+//line foo/bar.y:125
+	l = 125
+//line foo/bar.y:133
+	l = 133
+//line foo/bar.y:146
+	l = 146
+//line foo/bar.y:148
+//line foo/bar.y:153
+//line foo/bar.y:155
+	l = 155
+//line foo/bar.y:160
+
+//line foo/bar.y:164
+//line foo/bar.y:173
+
+//line foo/bar.y:178
+//line foo/bar.y:180
+//line foo/bar.y:185
+//line foo/bar.y:195
+//line foo/bar.y:197
+//line foo/bar.y:202
+//line foo/bar.y:204
+//line foo/bar.y:208
+//line foo/bar.y:211
+//line foo/bar.y:213
+//line foo/bar.y:215
+//line foo/bar.y:217
+//line foo/bar.y:221
+//line foo/bar.y:229
+//line foo/bar.y:236
+//line foo/bar.y:238
+//line foo/bar.y:240
+//line foo/bar.y:244
+//line foo/bar.y:249
+//line foo/bar.y:253
+//line foo/bar.y:257
+//line foo/bar.y:262
+//line foo/bar.y:267
+//line foo/bar.y:272
+	if l == f {
+//line foo/bar.y:277
+		panic("aie!")
+//line foo/bar.y:281
+	}
+//line foo/bar.y:285
+	return
+//line foo/bar.y:288
+//line foo/bar.y:290
+}
+
+//line foo/bar.y:293
+//line foo/bar.y:295