please ant with filenames, add comments

src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala

@@ -125,7 +125,7 @@ trait TreeAndTypeAnalysis extends Debugging {
   }
 }
 
-trait Analysis extends TreeAndTypeAnalysis { self: PatternMatching =>
+trait MatchAnalysis extends TreeAndTypeAnalysis { self: PatternMatching =>
   import PatternMatchingStats._
   import global.{Tree, Type, Symbol, CaseDef, atPos,
     Select, Block, ThisType, SingleType, NoPrefix, NoType, definitions, needsOuterTest,

src/compiler/scala/tools/nsc/transform/patmat/MatchCodeGen.scala

@@ -12,7 +12,12 @@ import scala.reflect.internal.util.Statistics
 import scala.reflect.internal.util.Position
 import scala.reflect.internal.util.NoPosition
 
-trait CodeGen { self: PatternMatching =>
+/** Factory methods used by TreeMakers to make the actual trees.
+ *
+ * We have two modes in which to emit trees: optimized (the default)
+ * and pure (aka "virtualized": match is parametric in its monad).
+ */
+trait MatchCodeGen { self: PatternMatching =>
   import PatternMatchingStats._
   import global.{nme, treeInfo, definitions, gen, Tree, Type, Symbol, NoSymbol,
     appliedType, NoType, MethodType, newTermName, Name,

src/compiler/scala/tools/nsc/transform/patmat/MatchOptimization.scala

@@ -13,7 +13,13 @@ import scala.reflect.internal.util.Statistics
 import scala.reflect.internal.util.Position
 import scala.reflect.internal.util.NoPosition
 
-trait Optimization { self: PatternMatching =>
+/** Optimize and analyze matches based on their TreeMaker-representation.
+ *
+ * The patmat translation doesn't rely on this, so it could be disabled in principle.
+ *
+ * TODO: split out match analysis
+ */
+trait MatchOptimization { self: PatternMatching =>
   import PatternMatchingStats._
   import global.{Tree, Type, Symbol, NoSymbol, CaseDef, atPos,
     ConstantType, Literal, Constant, gen, EmptyTree,

src/compiler/scala/tools/nsc/transform/patmat/MatchTranslation.scala

@@ -10,7 +10,9 @@ import scala.language.postfixOps
 import scala.collection.mutable
 import scala.reflect.internal.util.Statistics
 
-trait Translation { self: PatternMatching  =>
+/** Translate typed Trees that represent pattern matches into the patternmatching IR, defined by TreeMakers.
+ */
+trait MatchTranslation { self: PatternMatching  =>
   import PatternMatchingStats._
   import global.{phase, currentRun, Symbol,
     Apply, Bind, CaseDef, ClassInfoType, Ident, Literal, Match,
@@ -22,7 +24,7 @@ trait Translation { self: PatternMatching  =>
     repeatedToSeq, isRepeatedParamType, getProductArgs}
   import global.analyzer.{ErrorUtils, formalTypes}
 
-  trait MatchTranslation extends MatchMonadInterface { self: TreeMakers with CodegenCore =>
+  trait MatchTranslator extends MatchMonadInterface { self: TreeMakers with CodegenCore =>
     import typer.context
 
     // Why is it so difficult to say "here's a name and a context, give me any
@@ -669,5 +671,4 @@ trait Translation { self: PatternMatching  =>
       }
     }
   }
-
 }

src/compiler/scala/tools/nsc/transform/patmat/MatchTreeMakers.scala → src/compiler/scala/tools/nsc/transform/patmat/MatchTreeMaking.scala

@@ -6,18 +6,19 @@
 
 package scala.tools.nsc.transform.patmat
 
-//import scala.tools.nsc.{ast, symtab, typechecker, transform, Global}
-//import transform._
-//import typechecker._
-//import symtab._
 import scala.tools.nsc.symtab.Flags.{SYNTHETIC, ARTIFACT}
 import scala.language.postfixOps
 import scala.collection.mutable
 import scala.reflect.internal.util.Statistics
 import scala.reflect.internal.util.Position
 import scala.reflect.internal.util.NoPosition
 
-trait TreeMaking { self: PatternMatching =>
+/** Translate our IR (TreeMakers) into actual Scala Trees using the factory methods in MatchCodeGen.
+ *
+ * The IR is mostly concerned with sequencing, substitution, and rendering all necessary conditions,
+ * mostly agnostic to whether we're in optimized/pure (virtualized) mode.
+ */
+trait MatchTreeMaking { self: PatternMatching =>
   import PatternMatchingStats._
   import global.{Tree, Type, Symbol, CaseDef, atPos, settings,
     Select, Block, ThisType, SingleType, NoPrefix, NoType, needsOuterTest,

src/compiler/scala/tools/nsc/transform/patmat/PatternMatching.scala

@@ -17,8 +17,8 @@ import scala.reflect.internal.util.Position
 
 /** Translate pattern matching.
   *
-  * Either into optimized if/then/else's,
-  * or virtualized as method calls (these methods form a zero-plus monad), similar in spirit to how for-comprehensions are compiled.
+  * Either into optimized if/then/else's, or virtualized as method calls (these methods form a zero-plus monad),
+  * similar in spirit to how for-comprehensions are compiled.
   *
   * For each case, express all patterns as extractor calls, guards as 0-ary extractors, and sequence them using `flatMap`
   * (lifting the body of the case into the monad using `one`).
@@ -37,12 +37,12 @@ import scala.reflect.internal.util.Position
 trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
                       with Debugging
                       with Interface
-                      with Translation
-                      with TreeMaking
-                      with CodeGen
+                      with MatchTranslation
+                      with MatchTreeMaking
+                      with MatchCodeGen
                       with ScalaLogic
-                      with Analysis
-                      with Optimization {
+                      with MatchAnalysis
+                      with MatchOptimization {
   import global._
 
   val phaseName: String = "patmat"
@@ -70,13 +70,16 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
       case _ => super.transform(tree)
     }
 
-    def translator: MatchTranslation with CodegenCore = {
+    // TODO: only instantiate new match translator when localTyper has changed
+    // override def atOwner[A](tree: Tree, owner: Symbol)(trans: => A): A
+    // as this is the only time TypingTransformer changes it
+    def translator: MatchTranslator with CodegenCore = {
       new OptimizingMatchTranslator(localTyper)
     }
   }
 
-  class PureMatchTranslator(val typer: analyzer.Typer, val matchStrategy: Tree) extends MatchTranslation with TreeMakers with PureCodegen
-  class OptimizingMatchTranslator(val typer: analyzer.Typer)                    extends MatchTranslation with TreeMakers with MatchOptimizations
+  class PureMatchTranslator(val typer: analyzer.Typer, val matchStrategy: Tree) extends MatchTranslator with TreeMakers with PureCodegen
+  class OptimizingMatchTranslator(val typer: analyzer.Typer)                    extends MatchTranslator with TreeMakers with MatchOptimizations
 }
 
 trait HasGlobal {