SI-6281 macroArgs for defs with implicit args

macroArgs now correctly calculates the argss in case when a macro def
has implicit parameters.

Macro impls can never have implicit parameters other than type tag evidences,
so tags will always come in a separate parameter list w.r.t other parameters
of macro impls (which are in 1-to-1 correspondence with the parameters of
macro defs).

Example 1:
def w/o implicits: (params1)...(paramsN)
impl w/o tags: (params1')...(paramsN')

Example 2:
def w/o implicits: (params1)...(paramsN)
impl w tags: (params1')...(paramsN')(implicit tags)

Example 3:
def w implicits: (params1)...(paramsN)(implicit paramsN+1)
impl w/o tags: (params1')...(paramsN')(paramsN+1')
Note: paramsN+1' is not an implicit parameter list
because impls cannot have implicit parameters other than tags

Example 4:
def w implicits: (params1)...(paramsN)(implicit paramsN+1)
impl w tags: (params1')...(paramsN')(paramsN+1')(implicit tags)

Therefore we don't need to merge the argss.last (that correspond to implicit
parameters of macro defs) with tags, as it was incorrectly coded before.
We just need to append tags to argss.

Author: xeno-by

src/compiler/scala/tools/nsc/typechecker/Macros.scala

@@ -588,7 +588,7 @@ trait Macros extends scala.tools.reflect.FastTrack with Traces {
     val nullaryArgsEmptyParams = exprArgs.isEmpty && macroDef.paramss == ListOfNil
     if (argcDoesntMatch && !nullaryArgsEmptyParams) { typer.TyperErrorGen.MacroPartialApplicationError(expandee) }
 
-    var argss: List[List[Any]] = exprArgs.toList
+    val argss: List[List[Any]] = exprArgs.toList
     macroTraceVerbose("context: ")(context)
     macroTraceVerbose("argss: ")(argss)
 
@@ -597,9 +597,6 @@ trait Macros extends scala.tools.reflect.FastTrack with Traces {
         if (fastTrack(macroDef) validate context) argss
         else typer.TyperErrorGen.MacroPartialApplicationError(expandee)
       } else {
-        val binding = loadMacroImplBinding(macroDef)
-        macroTraceVerbose("binding: ")(binding)
-
         // if paramss have typetag context bounds, add an arglist to argss if necessary and instantiate the corresponding evidences
         // consider the following example:
         //
@@ -616,6 +613,8 @@ trait Macros extends scala.tools.reflect.FastTrack with Traces {
         // then T and U need to be inferred from the lexical scope of the call using `asSeenFrom`
         // whereas V won't be resolved by asSeenFrom and need to be loaded directly from `expandee` which needs to contain a TypeApply node
         // also, macro implementation reference may contain a regular type as a type argument, then we pass it verbatim
+        val binding = loadMacroImplBinding(macroDef)
+        macroTraceVerbose("binding: ")(binding)
         val tags = binding.signature filter (_ != -1) map (paramPos => {
           val targ = binding.targs(paramPos).tpe.typeSymbol
           val tpe = if (targ.isTypeParameterOrSkolem) {
@@ -633,14 +632,13 @@ trait Macros extends scala.tools.reflect.FastTrack with Traces {
             targ.tpe
           if (tpe.isConcrete) context.TypeTag(tpe) else context.AbsTypeTag(tpe)
         })
-        val hasImplicitParams = macroDef.paramss.flatten.lastOption exists (_.isImplicit)
-        argss = if (hasImplicitParams) argss.dropRight(1) :+ (tags ++ argss.last) else argss :+ tags
+        macroTraceVerbose("tags: ")(tags)
 
         // transforms argss taking into account varargness of paramss
         // note that typetag context bounds are only declared on macroImpls
         // so this optional arglist might not match macroDef's paramlist
         // nb! varargs can apply to any parameter section, not necessarily to the last one
-        mapWithIndex(argss)((as, i) => {
+        mapWithIndex(argss :+ tags)((as, i) => {
           val mapsToParamss = macroDef.paramss.indices contains i
           if (mapsToParamss) {
             val ps = macroDef.paramss(i)

test/files/run/macro-expand-implicit-argument.check

@@ -0,0 +1 @@
+List(1, 2, 3)

test/files/run/macro-expand-implicit-argument.flags

@@ -0,0 +1 @@
+-language:experimental.macros

test/files/run/macro-expand-implicit-argument/Macros_1.scala

@@ -0,0 +1,59 @@
+import annotation.tailrec
+import scala.math.{min, max}
+import scala.{specialized => spec}
+
+import language.experimental.macros
+
+import scala.reflect.{ClassTag, TypeTag}
+import scala.reflect.macros.Context
+
+object Macros {
+  def alloc[@spec A:ClassTag](src:Array[A], s1:Int, len:Int) = {
+    val as = Array.ofDim[A](len)
+    System.arraycopy(src, s1, as, 0, len)
+    as
+  }
+
+  /**
+   * Efficient alternative to Array.apply.
+   *
+   * "As seen on scala-internals!"
+   */
+  def array[A](as:A*)(implicit ct: ClassTag[A]) = macro arrayMacro[A]
+
+  /**
+   * Takes in something like:
+   *   ArrayUtil.alloc[Int](11, 22, 33, 44)(ct)
+   *
+   * and builds a tree like:
+   *   {
+   *     val arr:Array[Int] = ct.newArray(4)
+   *     arr.update(0, 11)
+   *     arr.update(1, 22)
+   *     arr.update(2, 33)
+   *     arr.update(3, 44)
+   *     arr
+   *   }
+   */
+  def arrayMacro[A:c.AbsTypeTag](c:Context)(as:c.Expr[A]*)(ct: c.Expr[ClassTag[A]]): c.Expr[Array[A]] = {
+    import c.mirror._
+    import c.universe._
+    def const(x:Int) = Literal(Constant(x))
+
+    val n = as.length
+    val arr = newTermName("arr")
+
+    val create = Apply(Select(ct.tree, "newArray"), List(const(n)))
+    val arrtpe = TypeTree(implicitly[c.AbsTypeTag[Array[A]]].tpe)
+    val valdef = ValDef(Modifiers(), arr, arrtpe, create)
+
+    val updates = (0 until n).map {
+      i => Apply(Select(Ident(arr), "update"), List(const(i), as(i).tree))
+    }
+
+    val exprs = Seq(valdef) ++ updates ++ Seq(Ident(arr))
+    val block = Block(exprs:_*)
+
+    c.Expr[Array[A]](block)
+  }
+}

test/files/run/macro-expand-implicit-argument/Test_2.scala

@@ -0,0 +1,4 @@
+object Test extends App {
+  import Macros._
+  println(array(1, 2, 3).toList)
+}