diff --git a/unstable/ast.go b/unstable/ast.go
index a9de8c2..6b21592 100644
--- a/unstable/ast.go
+++ b/unstable/ast.go
@@ -90,18 +90,6 @@ type Range struct {
 	Length uint32
 }
 
-func subsliceOffset(data []byte, subslice []byte) int {
-	if len(subslice) == 0 {
-		return len(data)
-	}
-	for i := range data {
-		if &data[i] == &subslice[0] {
-			return i
-		}
-	}
-	panic("subslice is not within data")
-}
-
 // Next returns a pointer to the next node, or nil if there is no next node.
 func (n *Node) Next() *Node {
 	if n.next < 0 {
diff --git a/unstable/parser.go b/unstable/parser.go
index e915404..c03bd2c 100644
--- a/unstable/parser.go
+++ b/unstable/parser.go
@@ -70,18 +70,6 @@ func (p *Parser) offsetOf(b []byte) int {
 	return len(p.data) - len(b)
 }
 
-// Range returns a range description that corresponds to a given slice of the
-// input. If the argument is not a subslice of the parser input, this function
-// panics.
-//
-// Prefer using ParserError.Offset directly for error position information.
-func (p *Parser) Range(b []byte) Range {
-	return Range{
-		Offset: uint32(subsliceOffset(p.data, b)), //nolint:gosec // TOML documents are small
-		Length: uint32(len(b)),                    //nolint:gosec // TOML documents are small
-	}
-}
-
 // rangeOfToken computes the Range of a token given the remaining bytes after the token.
 // This is used when the token was extracted from the beginning of some position,
 // and 'rest' is what remains after the token.
diff --git a/unstable/parser_test.go b/unstable/parser_test.go
index 7ffab8f..8aef7b6 100644
--- a/unstable/parser_test.go
+++ b/unstable/parser_test.go
@@ -674,7 +674,7 @@ key3 = "value3"
 	assert.Equal(t, []string{"key1", "key2", "key3"}, keys)
 }
 
-func TestRangeOffsetAfterComment(t *testing.T) {
+func TestErrorOffsetAfterComment(t *testing.T) {
 	input := []byte("# comment\n= \"value\"")
 
 	p := Parser{}
@@ -689,12 +689,11 @@ func TestRangeOffsetAfterComment(t *testing.T) {
 	if !errors.As(err, &perr) {
 		t.Fatalf("expected ParserError, got %T", err)
 	}
-	r := p.Range(perr.Highlight)
-	shape := p.Shape(r)
 
-	if r.Offset != 10 {
-		t.Errorf("Range offset: got %d, want 10", r.Offset)
+	if perr.Offset != 10 {
+		t.Errorf("offset: got %d, want 10", perr.Offset)
 	}
+	shape := p.Shape(Range{Offset: uint32(perr.Offset), Length: uint32(len(perr.Highlight))})
 	if shape.Start.Line != 2 || shape.Start.Column != 1 {
 		t.Errorf("position: got %d:%d, want 2:1", shape.Start.Line, shape.Start.Column)
 	}
@@ -753,8 +752,7 @@ func TestErrorHighlightPositions(t *testing.T) {
 			if !errors.As(err, &perr) {
 				t.Fatalf("expected ParserError, got %T", err)
 			}
-			r := p.Range(perr.Highlight)
-			shape := p.Shape(r)
+			shape := p.Shape(Range{Offset: uint32(perr.Offset), Length: uint32(len(perr.Highlight))})
 
 			if shape.Start.Line != e.wantLine {
 				t.Errorf("line: got %d, want %d", shape.Start.Line, e.wantLine)