FixItApplier: Non-empty insertions can conflict with other edits

(cherry picked from commit a00cbca)

Author: AnthonyLatsis

Sources/SwiftIDEUtils/FixItApplier.swift

@@ -103,7 +103,15 @@ public enum FixItApplier {
             return edit == remainingEdit
           }
 
-          return remainingEdit.range.overlaps(edit.range)
+          // Edits conflict in the following cases:
+          //
+          // - Their ranges have a common element.
+          // - One's range is empty and its lower bound is strictly within the
+          //   other's range. So 0..<2 also conflicts with 1..<1, but not with
+          //   0..<0 or 2..<2.
+          //
+          return edit.endUtf8Offset > remainingEdit.startUtf8Offset
+            && edit.startUtf8Offset < remainingEdit.endUtf8Offset
         }
 
         guard !shouldDropRemainingEdit() else {

Tests/SwiftIDEUtilsTest/FixItApplierTests.swift

@@ -232,9 +232,8 @@ class FixItApplierApplyEditsTests: XCTestCase {
         .init(range: 0..<5, replacement: "_"),  // Replacement
         .init(range: 2..<2, replacement: "a"),  // Insertion
       ],
-      // FIXME: This behavior where these edits are not considered overlapping doesn't feel desirable
       outputs: [
-        .init(oneOf: "_x = 1", "_ a= 1")
+        .init(oneOf: "_ = 1", "vaar x = 1")
       ]
     )
   }