Suppress common warnings in generated classes (#1028)

* Suppress common warnings in generated classes

Followup from #1023 (Resolves #1023 too). Since we can't do targeted deprecation suppressions, we can just stick with blanket deprecations suppressions for now. This also suppresses a couple other common issues with all our generated adapters.

Have just eyeballed the results for now, can add a proper test as a followup once #1014 is in

* Add redundant projection and re-enable -Werror

* Add tests for deprecation suppression

With -Werror enabled now we can actually check this

kotlin/tests/src/test/kotlin/com/squareup/moshi/kotlin/DualKotlinTest.kt

@@ -513,6 +513,7 @@ class DualKotlinTest(useReflection: Boolean) {
     assertThat(result).isEqualTo(instance)
   }
 
+  @Suppress("REDUNDANT_NULLABLE")
   @JsonClass(generateAdapter = true)
   data class TypeAliasNullability(
       val aShouldBeNonNull: A,

kotlin/tests/src/test/kotlin/com/squareup/moshi/kotlin/codegen/GeneratedAdaptersTest.kt

@@ -1169,6 +1169,22 @@ class GeneratedAdaptersTest {
     val instance = adapter.fromJson("""{"_links": "link", "_ids": "id" }""")!!
     assertThat(instance).isEqualTo(ClassWithFieldJson("link").apply { ids = "id" })
   }
+
+  /*
+   * These are a smoke test for https://github.com/square/moshi/issues/1023 to ensure that we
+   * suppress deprecation warnings for using deprecated properties or classes.
+   *
+   * Ideally when stubs are fixed to actually included Deprecated annotations, we could then only
+   * generate a deprecation suppression as needed and on targeted usages.
+   * https://youtrack.jetbrains.com/issue/KT-34951
+   */
+
+  @Deprecated("Deprecated for reasons")
+  @JsonClass(generateAdapter = true)
+  data class DeprecatedClass(val foo: String)
+
+  @JsonClass(generateAdapter = true)
+  data class DeprecatedProperty(@Deprecated("Deprecated for reasons") val foo: String)
 }
 
 // Regression test for https://github.com/square/moshi/issues/1022