Fix @public constructor vals in Scala 2 (#5485)

Author: trmckay

macros/src/main/scala-2/chisel3/internal/InstantiableMacro.scala

@@ -10,9 +10,17 @@ private[chisel3] object instantiableMacro {
 
   def impl(c: whitebox.Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
     import c.universe._
-    def processBody(stats: Seq[Tree]): (Seq[Tree], Iterable[Tree]) = {
+    def processBody(stats: Seq[Tree], paramss: List[List[ValDef]]): (Seq[Tree], Iterable[Tree]) = {
       val extensions = scala.collection.mutable.ArrayBuffer.empty[Tree]
       extensions += q"implicit val mg: chisel3.internal.MacroGenerated = new chisel3.internal.MacroGenerated {}"
+      paramss.flatten.foreach { param =>
+        if (
+          param.mods.hasFlag(c.universe.Flag.PARAMACCESSOR) &&
+          param.mods.annotations.toString.contains("new public()")
+        ) {
+          extensions += atPos(param.pos)(q"def ${param.name} = ___module._lookup(_.${param.name})")
+        }
+      }
       // Note the triple `_` prefixing `module` is to avoid conflicts if a user marks a 'val module'
       //  with @public; in this case, the lookup code is ambiguous between the generated `def module`
       //  function and the argument to the generated implicit class.
@@ -60,7 +68,7 @@ private[chisel3] object instantiableMacro {
         case q"$mods class $tpname[..$tparams] $ctorMods(...$paramss) extends { ..$earlydefns } with ..$parents { $self => ..$stats }" =>
           val defname = TypeName(tpname.toString + c.freshName())
           val instname = TypeName(tpname.toString + c.freshName())
-          val (newStats, extensions) = processBody(stats)
+          val (newStats, extensions) = processBody(stats, paramss)
           val argTParams = tparams.map(_.name)
           val allParents =
             if (hasIsInstantiable(parents)) parents
@@ -76,7 +84,7 @@ private[chisel3] object instantiableMacro {
         case q"$mods trait $tpname[..$tparams] extends { ..$earlydefns } with ..$parents { $self => ..$stats }" =>
           val defname = TypeName(tpname.toString + c.freshName())
           val instname = TypeName(tpname.toString + c.freshName())
-          val (newStats, extensions) = processBody(stats)
+          val (newStats, extensions) = processBody(stats, Nil)
           val argTParams = tparams.map(_.name)
           val allParents =
             if (hasIsInstantiable(parents)) parents

src/test/scala/chiselTests/experimental/hierarchy/DefinitionSpec.scala

@@ -549,7 +549,20 @@ class DefinitionSpec extends AnyFunSpec with Matchers with FileCheck {
              |""".stripMargin
         )
     }
-    it("(3.k): should work on unimplemented vals in abstract classes/traits") {
+    it("(3.k): should expose public constructor vals") {
+      @instantiable
+      class Foo(@public val x: Int, @public val y: Int = 0) extends Module
+      class Top extends Module {
+        val definition = Definition(new Foo(1))
+        definition.x should be(1)
+        definition.y should be(0)
+        val instance = Instance(definition)
+        instance.x should be(1)
+        instance.y should be(0)
+      }
+      ChiselStage.emitCHIRRTL(new Top) should include("module Foo :")
+    }
+    it("(3.l): should work on unimplemented vals in abstract classes/traits") {
       class Top() extends Module {
         val i = Definition(new ConcreteHasBlah())
         def f(d: Definition[HasBlah]): Unit = {
@@ -566,7 +579,7 @@ class DefinitionSpec extends AnyFunSpec with Matchers with FileCheck {
              |""".stripMargin
         )
     }
-    it("(3.l): should work on eithers") {
+    it("(3.m): should work on eithers") {
       class Top() extends Module {
         val i = Definition(new HasEither())
         i.x.map(x => mark(x, "xright")).left.map(x => mark(x, "xleft"))
@@ -584,7 +597,7 @@ class DefinitionSpec extends AnyFunSpec with Matchers with FileCheck {
              |""".stripMargin
         )
     }
-    it("(3.m): should work on tuple2") {
+    it("(3.n): should work on tuple2") {
       class Top() extends Module {
         val i = Definition(new HasTuple2())
         mark(i.xy._1, "x")
@@ -602,7 +615,7 @@ class DefinitionSpec extends AnyFunSpec with Matchers with FileCheck {
              |""".stripMargin
         )
     }
-    it("(3.n): should work on Mems/SyncReadMems") {
+    it("(3.o): should work on Mems/SyncReadMems") {
       class Top() extends Module {
         val i = Definition(new HasMems())
         mark(i.mem, "Mem")
@@ -620,7 +633,7 @@ class DefinitionSpec extends AnyFunSpec with Matchers with FileCheck {
              |""".stripMargin
         )
     }
-    it("(3.o): should not create memory ports") {
+    it("(3.p): should not create memory ports") {
       class Top() extends Module {
         val i = Definition(new HasMems())
         i.mem(0) := 100.U // should be illegal!
@@ -631,7 +644,7 @@ class DefinitionSpec extends AnyFunSpec with Matchers with FileCheck {
         "Cannot create a memory port in a different module (Top) than where the memory is (HasMems)."
       )
     }
-    it("(3.p): should work on HasTarget") {
+    it("(3.q): should work on HasTarget") {
       class Top() extends Module {
         val i = Definition(new HasHasTarget)
         mark(i.x, "x")
@@ -645,7 +658,7 @@ class DefinitionSpec extends AnyFunSpec with Matchers with FileCheck {
              |""".stripMargin
         )
     }
-    it("(3.q): should work on Tuple5 with a Module in it") {
+    it("(3.r): should work on Tuple5 with a Module in it") {
       class Top() extends Module {
         val defn = Definition(new HasTuple5())
         val (3, w: UInt, "hi", inst: Instance[AddOne], l) = defn.tup