Merge pull request #2730 from scalamacros/ticket/7657

SI-7657 clarifies the "macro overrides method" rule

7 files changed, 40 insertions, 20 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index 03ce710700..9c374e85ea 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -225,7 +225,7 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
      *    1.8.1  M's type is a subtype of O's type, or
      *    1.8.2  M is of type []S, O is of type ()T and S <: T, or
      *    1.8.3  M is of type ()S, O is of type []T and S <: T, or
-     *    1.9.  If M is a macro def, O cannot be deferred.
+     *    1.9.  If M is a macro def, O cannot be deferred unless there's a concrete method overriding O.
      *    1.10. If M is not a macro def, O cannot be a macro def.
      *  2. Check that only abstract classes have deferred members
      *  3. Check that concrete classes do not have deferred definitions
@@ -417,7 +417,7 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
           } else if (other.isValue && other.isLazy && !other.isSourceMethod && !other.isDeferred &&
                      member.isValue && !member.isLazy) {
             overrideError("must be declared lazy to override a concrete lazy value")
-          } else if (other.isDeferred && member.isTermMacro) { // (1.9)
+          } else if (other.isDeferred && member.isTermMacro && member.extendedOverriddenSymbols.forall(_.isDeferred)) { // (1.9)
             overrideError("cannot override an abstract method")
           } else if (other.isTermMacro && !member.isTermMacro) { // (1.10)
             overrideError("cannot override a macro")
diff --git a/test/files/neg/macro-override-macro-overrides-abstract-method-b.check b/test/files/neg/macro-override-macro-overrides-abstract-method-b.check
index 895e0dca50..cde3dbdbe8 100644
--- a/test/files/neg/macro-override-macro-overrides-abstract-method-b.check
+++ b/test/files/neg/macro-override-macro-overrides-abstract-method-b.check
@@ -1,5 +1,11 @@
-Impls_Macros_1.scala:12: error: overriding method foo in trait Foo of type (x: Int)Int;
- macro method foo cannot override an abstract method
-  def foo(x: Int) = macro Impls.impl
-      ^
-one error found
+Test_2.scala:3: error: anonymous class $anon inherits conflicting members:
+  macro method t in trait C of type ()Unit  and
+  method t in trait A of type ()Unit
+(Note: this can be resolved by declaring an override in anonymous class $anon.)
+  val c2 = new C with A {}
+               ^
+Test_2.scala:5: error: overriding macro method t in trait C of type ()Unit;
+ method t cannot override a macro
+  val c4 = new C with A { override def t(): Unit = () }
+                                       ^
+two errors found
diff --git a/test/files/neg/macro-override-macro-overrides-abstract-method-b/Impls_Macros_1.scala b/test/files/neg/macro-override-macro-overrides-abstract-method-b/Impls_Macros_1.scala
index e43264f52f..f5b2555aa5 100644
--- a/test/files/neg/macro-override-macro-overrides-abstract-method-b/Impls_Macros_1.scala
+++ b/test/files/neg/macro-override-macro-overrides-abstract-method-b/Impls_Macros_1.scala
@@ -1,13 +1,8 @@
-import scala.reflect.macros.{Context => Ctx}
+import scala.reflect.macros.Context
+import language.experimental.macros
 
-object Impls {
-  def impl(c: Ctx)(x: c.Expr[Int]) = x
-}
+trait T { def t(): Unit }
+trait A { def t(): Unit = () }
 
-trait Foo {
-  def foo(x: Int): Int
-}
-
-object Macros extends Foo {
-  def foo(x: Int) = macro Impls.impl
-}
+object Macro { def t(c: Context)(): c.Expr[Unit] = c.universe.reify(()) }
+trait C extends T { self: A => override def t(): Unit = macro Macro.t }
diff --git a/test/files/neg/macro-override-macro-overrides-abstract-method-b/Test_2.scala b/test/files/neg/macro-override-macro-overrides-abstract-method-b/Test_2.scala
index 08fff30baf..9b4c8e35f0 100644
--- a/test/files/neg/macro-override-macro-overrides-abstract-method-b/Test_2.scala
+++ b/test/files/neg/macro-override-macro-overrides-abstract-method-b/Test_2.scala
@@ -1,4 +1,6 @@
 object Test extends App {
-  val designator: Foo = Macros
-  designator.foo(42)
+  val c1 = new A with C {}
+  val c2 = new C with A {}
+  val c3 = new C with A { override def t(): Unit = macro Macro.t }
+  val c4 = new C with A { override def t(): Unit = () }
 }
\ No newline at end of file
diff --git a/test/files/run/t7657.check b/test/files/run/t7657.check
new file mode 100644
index 0000000000..c25d8d1c1b
--- /dev/null
+++ b/test/files/run/t7657.check
@@ -0,0 +1,3 @@
+()
+()
+()
diff --git a/test/files/run/t7657/Macros_1.scala b/test/files/run/t7657/Macros_1.scala
new file mode 100644
index 0000000000..b1e31aa2dd
--- /dev/null
+++ b/test/files/run/t7657/Macros_1.scala
@@ -0,0 +1,8 @@
+import scala.reflect.macros.Context
+import language.experimental.macros
+
+trait T { def t(): Unit }
+abstract class A extends T { override def t(): Unit = () }
+
+object Macro { def t(c: Context)(): c.Expr[Unit] = c.universe.reify(()) }
+class C extends A { override def t(): Unit = macro Macro.t }
diff --git a/test/files/run/t7657/Test_2.scala b/test/files/run/t7657/Test_2.scala
new file mode 100644
index 0000000000..5cc46b6aa1
--- /dev/null
+++ b/test/files/run/t7657/Test_2.scala
@@ -0,0 +1,6 @@
+object Test extends App {
+  val c = new C()
+  println(c.t())
+  println((c: T).t())
+  println((c: A).t())
+}
\ No newline at end of file