diff --git a/src/index.ts b/src/index.ts
index fde615d..c9fe663 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -241,6 +241,10 @@ export class SourceRegion {
     return this.source.sliceByCp(this.span.start.index, this.span.end.index);
   }
 
+  stringOf(span: Span): string {
+    return this.subRegion(span).toString();
+  }
+
   // Returns a Span for the given line (1-based index).
   getLineSpan(line: number, stripNewlines = true): Span {
     if (line < this.span.start.line || line > this.span.end.line) {