[Function builders] Add tests for function builders on protocol requirements

Author: DougGregor

test/ModuleInterface/function_builders.swift

@@ -47,3 +47,10 @@ public struct UsesBuilderProperty {
   // CHECK: public func myFunc(@FunctionBuilders.TupleBuilder fn: () -> ())
   public func myFunc(@TupleBuilder fn: () -> ()) {}
 }
+
+public protocol ProtocolWithBuilderProperty {
+  associatedtype Assoc
+  
+  // CHECK: @FunctionBuilders.TupleBuilder var myVar: Self.Assoc { get }
+  @TupleBuilder var myVar: Assoc { get }
+}

test/Serialization/function_builders.swift

@@ -0,0 +1,36 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -emit-module -o %t %s
+// RUN: %target-swift-ide-test(mock-sdk: %clang-importer-sdk) -print-module -skip-deinit=false -module-to-print=function_builders -I %t -source-filename=%s | %FileCheck %s
+
+@_functionBuilder
+public struct TupleBuilder {
+  public static func buildBlock<T1, T2>(_ t1: T1, _ t2: T2) -> (T1, T2) {
+    return (t1, t2)
+  }
+
+  public static func buildBlock<T1, T2, T3>(_ t1: T1, _ t2: T2, _ t3: T3)
+      -> (T1, T2, T3) {
+    return (t1, t2, t3)
+  }
+
+  public static func buildBlock<T1, T2, T3, T4>(_ t1: T1, _ t2: T2, _ t3: T3, _ t4: T4)
+      -> (T1, T2, T3, T4) {
+    return (t1, t2, t3, t4)
+  }
+
+  public static func buildBlock<T1, T2, T3, T4, T5>(
+    _ t1: T1, _ t2: T2, _ t3: T3, _ t4: T4, _ t5: T5
+  ) -> (T1, T2, T3, T4, T5) {
+    return (t1, t2, t3, t4, t5)
+  }
+
+  public static func buildDo<T>(_ value: T) -> T { return value }
+  public static func buildIf<T>(_ value: T?) -> T? { return value }
+}
+
+public protocol ProtocolWithBuilderProperty {
+  associatedtype Assoc
+  
+  // CHECK: @TupleBuilder var myVar: Self.Assoc { get }
+  @TupleBuilder var myVar: Assoc { get }
+}