Add regression test for bug already fixed

Author: slavapestov

test/decl/protocol/req/issue-71216.swift

@@ -0,0 +1,18 @@
+// RUN: %target-typecheck-verify-swift
+
+protocol RequiresIntFunction {
+  associatedtype A = ()
+  func intFunction(_ x: Int, _ a: A) -> Bool
+}
+
+struct Regular<A>: RequiresIntFunction {
+  func intFunction(_ x: Int, _ a: A) -> Bool {
+    true
+  }
+}
+
+struct GenericBad<A>: RequiresIntFunction {
+  func intFunction(_ x: some FixedWidthInteger, _ a: A) -> Bool {
+    true
+  }
+}

test/decl/protocol/req/rdar123339514.swift

@@ -0,0 +1,19 @@
+// RUN: %target-swift-frontend -emit-silgen %s -disable-experimental-associated-type-inference
+// RUN: %target-swift-frontend -emit-silgen %s -enable-experimental-associated-type-inference
+
+public struct G<A, B, C>: P {
+  public typealias D = G<A, C, B>
+  public typealias E = G<A, S, C>
+  public typealias F = G<A, B, S>
+}
+
+public struct S {}
+
+public protocol P {
+  associatedtype A
+  associatedtype B
+  associatedtype C
+  associatedtype D: P where D.A == A, D.D == Self
+  associatedtype E: P where E.C == C, E.B == S, E.A == A, E.E == E
+  associatedtype F: P where F.C == S, F.B == B, F.A == A, F.F == F
+}