fix: avoid crash when moving a zero-length range (#307)

Co-authored-by: Anthony Fu <github@antfu.me>

Author: sarathfrancis90

src/MagicString.ts

@@ -484,6 +484,9 @@ export default class MagicString {
     end = end + this.offset
     index = index + this.offset
 
+    if (start === end)
+      return this
+
     if (index >= start && index <= end)
       throw new Error('Cannot move a selection inside itself')
 

test/MagicString.test.ts

@@ -876,6 +876,15 @@ describe('magicString', () => {
       assert.throws(() => s.move(3, 6, 6), /Cannot move a selection inside itself/)
     })
 
+    it('does nothing when moving a zero-length range', () => {
+      const s = new MagicString('abcdefghijkl')
+
+      assert.doesNotThrow(() => s.move(0, 0, 6))
+      assert.doesNotThrow(() => s.move(5, 5, 0))
+
+      assert.equal(s.toString(), 'abcdefghijkl')
+    })
+
     it('allows edits of moved content', () => {
       const s1 = new MagicString('abcdefghijkl')