Special-case comparisons of ranges in __checkBinaryOperation().

Sources/Testing/Expectations/ExpectationChecking+Macro.swift

@@ -165,7 +165,7 @@ private func _callBinaryOperator<T, U, R>(
 ///
 /// - Warning: This function is used to implement the `#expect()` and
 ///   `#require()` macros. Do not call it directly.
-public func __checkBinaryOperation<T, U>(
+@_disfavoredOverload public func __checkBinaryOperation<T, U>(
   _ lhs: T, _ op: (T, () -> U) -> Bool, _ rhs: @autoclosure () -> U,
   expression: __Expression,
   comments: @autoclosure () -> [Comment],
@@ -594,7 +594,7 @@ public func __checkPropertyAccess<T, U>(
 ///
 /// - Warning: This function is used to implement the `#expect()` and
 ///   `#require()` macros. Do not call it directly.
-public func __checkBinaryOperation<T>(
+@_disfavoredOverload public func __checkBinaryOperation<T>(
   _ lhs: T, _ op: (T, () -> T) -> Bool, _ rhs: @autoclosure () -> T,
   expression: __Expression,
   comments: @autoclosure () -> [Comment],
@@ -660,6 +660,34 @@ public func __checkBinaryOperation(
   )
 }
 
+/// Check that an expectation has passed after a condition has been evaluated
+/// and throw an error if it failed.
+///
+/// This overload is necessary because ranges are collections and satisfy the
+/// requirements for the difference-calculating overload above, but it doesn't
+/// make sense to diff them and very large ranges can cause overflows or hangs.
+///
+/// - Warning: This function is used to implement the `#expect()` and
+///   `#require()` macros. Do not call it directly.
+public func __checkBinaryOperation<T, U>(
+  _ lhs: T, _ op: (T, () -> U) -> Bool, _ rhs: @autoclosure () -> U,
+  expression: __Expression,
+  comments: @autoclosure () -> [Comment],
+  isRequired: Bool,
+  sourceLocation: SourceLocation
+) -> Result<Void, any Error> where T: RangeExpression, U: RangeExpression {
+  let (condition, rhs) = _callBinaryOperator(lhs, op, rhs)
+  return __checkValue(
+    condition,
+    expression: expression,
+    expressionWithCapturedRuntimeValues: expression.capturingRuntimeValues(lhs, rhs),
+    difference: nil,
+    comments: comments(),
+    isRequired: isRequired,
+    sourceLocation: sourceLocation
+  )
+}
+
 /// Check that an expectation has passed after a condition has been evaluated
 /// and throw an error if it failed.
 ///

Tests/TestingTests/IssueTests.swift

@@ -1104,6 +1104,38 @@ final class IssueTests: XCTestCase {
     }.run(configuration: configuration)
   }
 
+  func testCollectionDifferenceSkippedForRanges() async {
+    var configuration = Configuration()
+    configuration.eventHandler = { event, _ in
+      guard case let .issueRecorded(issue) = event.kind else {
+        return
+      }
+      guard case let .expectationFailed(expectation) = issue.kind else {
+        XCTFail("Unexpected issue kind \(issue.kind)")
+        return
+      }
+      XCTAssertNil(expectation.differenceDescription)
+    }
+
+    await Test {
+      let range_int8: ClosedRange<Int> = Int(Int8.min)...Int(Int8.max)
+      let range_uint16: ClosedRange<Int> = Int(UInt16.min)...Int(UInt16.max)
+      let range_int64: ClosedRange<Int> = Int(Int64.min)...Int(Int64.max)
+
+      #expect(range_int8 == (-127)...127, "incorrect min")
+      #expect(range_int8 == (-128)...128, "incorrect max")
+      #expect(range_int8 == 0...0, "both incorrect")
+
+      #expect(range_uint16 == (-1)...65_535, "incorrect min")
+      #expect(range_uint16 == 0...65_534, "incorrect max")
+      #expect(range_uint16 == 1...1, "both incorrect")
+
+      #expect(range_int64 == (-9_223_372_036_854_775_807)...9_223_372_036_854_775_807, "incorrect min")
+      #expect(range_int64 == (-9_223_372_036_854_775_808)...9_223_372_036_854_775_806, "incorrect max")
+      #expect(range_int64 == 0...0, "both incorrect")
+    }.run(configuration: configuration)
+  }
+
   func testNegatedExpressions() async {
     var configuration = Configuration()
     configuration.eventHandler = { event, _ in