SI-8954 Make @deprecated{Overriding,Inheritance} aware of @deprecated.

This makes sure that:
 - there is no warning for a @deprecated class inheriting a
   @deprecatedInheritance class
 - there is no warning for a @deprecated method overriding a
   @deprecatedOverriding method
 - there is no "deprecation won't work" warning when overriding a member
   of a @deprecatedInheritance class with a @deprecated member
 - the above works even if the classes/methods are indirectly deprecated
   (i.e. enclosed in something @deprecated)

This should remove quite a few useless deprecation warnings from the
library.

3 files changed, 53 insertions, 0 deletions

diff --git a/test/files/pos/t8954.flags b/test/files/pos/t8954.flags
new file mode 100644
index 0000000000..7de3c0f3ee
--- /dev/null
+++ b/test/files/pos/t8954.flags
@@ -0,0 +1 @@
+-Xfatal-warnings -deprecation
diff --git a/test/files/pos/t8954/t1.scala b/test/files/pos/t8954/t1.scala
new file mode 100644
index 0000000000..3986d9f3b5
--- /dev/null
+++ b/test/files/pos/t8954/t1.scala
@@ -0,0 +1,13 @@
+package scala.foo
+
+// 1. a class about to be made final
+@deprecatedInheritance class A {
+  def foo(): Unit = ???
+}
+
+// 1.1:
+// - no inheritance warning because same file
+// - no "override non-deprecated member" because @deprecatedInheritance
+class B2 extends A {
+  @deprecated("","") override def foo(): Unit = ???
+}
diff --git a/test/files/pos/t8954/t2.scala b/test/files/pos/t8954/t2.scala
new file mode 100644
index 0000000000..4def127832
--- /dev/null
+++ b/test/files/pos/t8954/t2.scala
@@ -0,0 +1,39 @@
+package scala.foo
+
+// 1.2 deprecated children should be fine...
+@deprecated("", "") class B extends A {
+
+  // 1.3 and shouldn't trigger the
+  // "overriding non-deprecated parent" warning
+  override def foo(): Unit = ???
+}
+
+@deprecated("","") class F {
+  // 1.4 a class inside a deprecated class should work too
+  class G extends A
+}
+
+// 2. a method about to be made final
+class C {
+  @deprecatedOverriding def foo(): Unit = ???
+}
+
+// 2.1 overriding with a deprecated def should be fine
+// and also shoudln't trigger the "deprecation is useless"
+// warning
+class D extends C {
+  @deprecated("","") override def foo(): Unit = ???
+}
+
+// 2.2 overriding from a deprecated class should be fine
+@deprecated("","") class E extends C {
+  override def foo(): Unit = ???
+}
+
+// 2.3 overriding from deeper inside a deprecated class
+// should work too
+@deprecated("","") class H {
+  class I extends C {
+    override def foo(): Unit = ???
+  }
+}