[SR-15049] Adding regression tests for ticket

Author: LucianoPAlmeida

test/Concurrency/sr15049.swift

@@ -0,0 +1,20 @@
+// RUN: %target-typecheck-verify-swift -disable-availability-checking
+// REQUIRES: concurrency
+
+func testAsyncSequenceTypedPattern<Seq: AsyncSequence>(_ seq: Seq) async throws where Seq.Element == Int {
+   async let result: Int = seq.reduce(0) { $0 + $1 } // OK
+   // expected-warning@-1{{immutable value 'result' was never used; consider replacing with '_' or removing it}}
+}
+
+func testAsyncSequenceTypedPattern1<Seq: AsyncSequence>(_ seq: Seq) async throws where Seq.Element == Int {
+   async let _: Int = seq.reduce(0) { $0 + $1 } // OK
+}
+
+func testAsyncSequence<Seq: AsyncSequence>(_ seq: Seq) async throws where Seq.Element == Int {
+   async let result = seq.reduce(0) { $0 + $1 } // OK
+   // expected-warning@-1{{initialization of immutable value 'result' was never used; consider replacing with assignment to '_' or removing it}}
+}
+
+func testAsyncSequence1<Seq: AsyncSequence>(_ seq: Seq) async throws where Seq.Element == Int {
+   async let _ = seq.reduce(0) { $0 + $1 } // OK
+}