diff --git a/test/Constraints/bidirectional_conversions.swift b/test/Constraints/bidirectional_conversions.swift
new file mode 100644
index 0000000000000..de5077c507a32
--- /dev/null
+++ b/test/Constraints/bidirectional_conversions.swift
@@ -0,0 +1,113 @@
+// RUN: %target-typecheck-verify-swift
+// REQUIRES: objc_interop
+
+import Foundation
+import CoreGraphics
+
+/////////////
+
+struct G<T> {  // expected-note {{arguments to generic parameter 'T' ('CGFloat?' and 'CGFloat') are expected to be equal}}
+  var t: T
+}
+
+func foo1(x: (x: Int, y: Int)?, y: (Int, Int)) -> G<(x: Int, y: Int)> {
+  let g = G(t: x ?? y)
+  return g
+}
+
+func foo2(x: (Int, Int)?, y: (x: Int, y: Int)) -> G<(Int, Int)> {
+  let g = G(t: x ?? y)
+  return g
+}
+
+func foo3(x: (@convention(block) () -> ())?, y: @escaping () -> ()) -> G<@convention(block) () -> ()> {
+  let g = G(t: x ?? y)
+  return g
+}
+
+func foo4(x: (() -> ())?, y: @escaping @convention(block) () -> ()) -> G<() -> ()> {
+  let g = G(t: x ?? y)
+  return g
+}
+
+func foo5(x: CGFloat?, y: Double) -> G<CGFloat> {
+  let g = G(t: x ?? y)
+  // FIXME
+  return g  // expected-error {{cannot convert return expression of type 'G<CGFloat?>' to return type 'G<CGFloat>'}}
+}
+
+func foo6(x: Double?, y: CGFloat) -> G<Double> {
+  let g = G(t: x ?? y)
+  return g
+}
+
+/////////////
+
+func id<T>(_: T) -> T {}
+
+func bar1(x: (x: Int, y: Int)) {
+  func f(_: (Int, Int)) {}
+  f(id(x))
+}
+
+func bar2(x: (Int, Int)) {
+  func f(_: (x: Int, y: Int)) {}
+  f(id(x))
+}
+
+func bar3(x: @escaping () -> ()) {
+  func f(_: @escaping @convention(block) () -> ()) {}
+  // FIXME
+  f(id(x))  // expected-error {{conflicting arguments to generic parameter 'T' ('@convention(block) () -> ()' vs. '() -> ()')}}
+}
+
+func bar4(x: @escaping @convention(block) () -> ()) {
+  func f(_: @escaping () -> ()) {}
+  // FIXME
+  f(id(x))  // expected-error {{conflicting arguments to generic parameter 'T' ('() -> ()' vs. '@convention(block) () -> ()')}}
+}
+
+func bar5(x: Double) {
+  func f(_: CGFloat) {}
+  f(id(x))
+}
+
+func bar6(x: CGFloat) {
+  func f(_: Double) {}
+  f(id(x))
+}
+
+/////////////
+
+func unwrap<T>(_: T?) -> T {}
+
+func baz1(x: (x: Int, y: Int)?) {
+  func f(_: (Int, Int)) {}
+  f(unwrap(x))
+}
+
+func baz2(x: (Int, Int)?) {
+  func f(_: (x: Int, y: Int)) {}
+  f(unwrap(x))
+}
+
+func baz3(x: (() -> ())?) {
+  func f(_: @escaping @convention(block) () -> ()) {}
+  f(unwrap(x))
+}
+
+func baz4(x: (@convention(block) () -> ())?) {
+  func f(_: @escaping () -> ()) {}
+  f(unwrap(x))
+}
+
+func baz5(x: Double?) {
+  func f(_: CGFloat) {}
+  f(unwrap(x))
+}
+
+func baz6(x: CGFloat?) {
+  func f(_: Double) {}
+  f(unwrap(x))
+}
+
diff --git a/validation-test/Sema/type_checker_perf/fast/swift_docc.swift b/validation-test/Sema/type_checker_perf/fast/swift_docc.swift
new file mode 100644
index 0000000000000..e36687f5a3aad
--- /dev/null
+++ b/validation-test/Sema/type_checker_perf/fast/swift_docc.swift
@@ -0,0 +1,35 @@
+// RUN: %target-typecheck-verify-swift -solver-scope-threshold=2000
+
+// We don't use anything from Foundation below, but Foundation adds a
+// large number of == overloads. Import it if we can, because it makes
+// the problem instance harder.
+#if canImport(Foundation)
+import Foundation
+#endif
+
+struct Graph {
+  func nodeWithReference(_: Int) -> Node? { fatalError() }
+}
+
+struct DocumentationContext {
+  func parents(of: Int) -> [Int] { fatalError() }
+  var topicGraph: Graph
+}
+
+struct Node {
+  var reference: Int
+  var kind: Kind
+
+  enum Kind {
+    case tutorialTableOfContents
+    case chapter
+    case volume
+  }
+}
+
+func analyze(_ node: Node, context: DocumentationContext) {
+  _ = context.parents(of: node.reference)
+    .compactMap({ context.topicGraph.nodeWithReference($0) })
+    .first(where: { $0.kind == .tutorialTableOfContents || $0.kind == .chapter || $0.kind == .volume })
+}
+