Support @binaryAPI on private constructors

Author: nicolasstucki

compiler/src/dotty/tools/dotc/typer/Checking.scala

@@ -530,7 +530,7 @@ object Checking {
       if sym.is(Enum) then fail(em"@binaryAPI cannot be used on enum definitions.")
       else if sym.isType && !sym.is(Module) && !(sym.is(Given) || sym.companionModule.is(Given)) then fail(em"@binaryAPI cannot be used on ${sym.showKind} definitions")
       else if !sym.owner.isClass && !(sym.is(Param) && sym.owner.isConstructor) then fail(em"@binaryAPI cannot be used on local definitions.")
-      else if sym.is(Private) then fail(em"@binaryAPI cannot be used on private definitions.\n\nCould the definition `private[${sym.owner.name}]` or `protected` instead or use `@binaryAPIAccessor` instead of `@binaryAPI`.")
+      else if sym.is(Private) && !sym.isConstructor then fail(em"@binaryAPI cannot be used on private definitions.\n\nCould the definition `private[${sym.owner.name}]` or `protected` instead or use `@binaryAPIAccessor` instead of `@binaryAPI`.")
     if sym.hasAnnotation(defn.BinaryAPIAccessorAnnot) then
       if sym.is(Enum) then fail(em"@binaryAPIAccessor cannot be used on enum definitions.")
       else if sym.isConstructor then fail(em"@binaryAPIAccessor cannot be used on constructors.")

tests/neg/binaryAPI.check

@@ -22,30 +22,6 @@
 19 |  @binaryAPI case B(a: Int) // error
    |                  ^
    |                  @binaryAPI cannot be used on enum definitions.
--- Error: tests/neg/binaryAPI.scala:22:9 -------------------------------------------------------------------------------
-22 |class Foo @binaryAPI private (x: Int): // error
-   |         ^
-   | @binaryAPI cannot be used on private definitions.
-   |
-   | Could the definition `private[Foo]` or `protected` instead or use `@binaryAPIAccessor` instead of `@binaryAPI`.
--- Error: tests/neg/binaryAPI.scala:23:25 ------------------------------------------------------------------------------
-23 |  @binaryAPI private def this(x: Int, y: Int) = this(x + y) // error
-   |                         ^
-   | @binaryAPI cannot be used on private definitions.
-   |
-   | Could the definition `private[Foo]` or `protected` instead or use `@binaryAPIAccessor` instead of `@binaryAPI`.
--- Error: tests/neg/binaryAPI.scala:25:9 -------------------------------------------------------------------------------
-25 |class Bar @binaryAPI private[this] (x: Int): // error
-   |         ^
-   | @binaryAPI cannot be used on private definitions.
-   |
-   | Could the definition `private[Bar]` or `protected` instead or use `@binaryAPIAccessor` instead of `@binaryAPI`.
--- Error: tests/neg/binaryAPI.scala:26:31 ------------------------------------------------------------------------------
-26 |  @binaryAPI private[this] def this(x: Int, y: Int) = this(x + y) // error
-   |                               ^
-   | @binaryAPI cannot be used on private definitions.
-   |
-   | Could the definition `private[Bar]` or `protected` instead or use `@binaryAPIAccessor` instead of `@binaryAPI`.
 -- Error: tests/neg/binaryAPI.scala:5:16 -------------------------------------------------------------------------------
 5 |@binaryAPI type A // error
   |                ^

tests/neg/binaryAPI.scala

@@ -17,10 +17,3 @@ def f(@binaryAPI x: Int) = 3 // error
 enum Enum2:
   @binaryAPI case A // error
   @binaryAPI case B(a: Int) // error
-
-
-class Foo @binaryAPI private (x: Int): // error
-  @binaryAPI private def this(x: Int, y: Int) = this(x + y) // error
-
-class Bar @binaryAPI private[this] (x: Int): // error
-  @binaryAPI private[this] def this(x: Int, y: Int) = this(x + y) // error

tests/pos/binaryAPI.scala

@@ -128,11 +128,15 @@ package constructors {
   class Foo @binaryAPI private[constructors] (x: Int):
     @binaryAPI private[constructors] def this(x: Int, y: Int) = this(x + y)
 
+  class Bar @binaryAPI(x: Int):
+    @binaryAPI private def this(x: Int, y: Int) = this(x + y)
+    inline def bar: Bar = new Bar(x, x)
+
   inline def newFoo(x: Int) = new Foo(x)
   inline def newFoo(x: Int, y: Int) = new Foo(x, y)
 }
 
 def testConstructors =
-  import constructors.*
-  val f = newFoo(1)
-  val g = newFoo(1, 2)
+  val f = constructors.newFoo(1)
+  val g = constructors.newFoo(1, 2)
+  val h = new constructors.Bar(1).bar