Avoid intermediate mapping in ZincWorkerImpl (#2661)

Profiled Mill compiling Mill itself and 0.07% of the time was spent in
mapping the result of `compileMixed0` to `CompilationResult`.
This changes the `compileInternal` method to already use the right types
so less conversions are needed.

Pull request: #2661

scalalib/worker/src/mill/scalalib/worker/ZincWorkerImpl.scala

@@ -297,26 +297,6 @@ class ZincWorkerImpl(
       reporter: Option[CompileProblemReporter],
       reportCachedProblems: Boolean
   )(implicit ctx: ZincWorkerApi.Ctx): Result[CompilationResult] = {
-
-    for (
-      res <- compileJava0(
-        upstreamCompileOutput = upstreamCompileOutput.map(c => (c.analysisFile, c.classes.path)),
-        sources = sources,
-        compileClasspath = compileClasspath,
-        javacOptions = javacOptions,
-        reporter = reporter,
-        reportCachedProblems = reportCachedProblems
-      )
-    ) yield CompilationResult(res._1, PathRef(res._2))
-  }
-  def compileJava0(
-      upstreamCompileOutput: Seq[(os.Path, os.Path)],
-      sources: Agg[os.Path],
-      compileClasspath: Agg[os.Path],
-      javacOptions: Seq[String],
-      reporter: Option[CompileProblemReporter],
-      reportCachedProblems: Boolean
-  )(implicit ctx: ZincWorkerApi.Ctx): Result[(os.Path, os.Path)] = {
     compileInternal(
       upstreamCompileOutput = upstreamCompileOutput,
       sources = sources,
@@ -342,37 +322,6 @@ class ZincWorkerImpl(
       reporter: Option[CompileProblemReporter],
       reportCachedProblems: Boolean
   )(implicit ctx: ZincWorkerApi.Ctx): Result[CompilationResult] = {
-
-    for (
-      res <- compileMixed0(
-        upstreamCompileOutput.map(c => (c.analysisFile, c.classes.path)),
-        sources,
-        compileClasspath,
-        javacOptions,
-        scalaVersion,
-        scalaOrganization,
-        scalacOptions,
-        compilerClasspath,
-        scalacPluginClasspath,
-        reporter,
-        reportCachedProblems
-      )
-    ) yield CompilationResult(res._1, PathRef(res._2))
-  }
-
-  def compileMixed0(
-      upstreamCompileOutput: Seq[(os.Path, os.Path)],
-      sources: Agg[os.Path],
-      compileClasspath: Agg[os.Path],
-      javacOptions: Seq[String],
-      scalaVersion: String,
-      scalaOrganization: String,
-      scalacOptions: Seq[String],
-      compilerClasspath: Agg[PathRef],
-      scalacPluginClasspath: Agg[PathRef],
-      reporter: Option[CompileProblemReporter],
-      reportOldProblems: Boolean
-  )(implicit ctx: ZincWorkerApi.Ctx): Result[(os.Path, os.Path)] = {
     withCompilers(
       scalaVersion = scalaVersion,
       scalaOrganization = scalaOrganization,
@@ -388,7 +337,7 @@ class ZincWorkerImpl(
         scalacOptions = scalacOptions,
         compilers = compilers,
         reporter = reporter,
-        reportOldProblems: Boolean
+        reportCachedProblems: Boolean
       )
     }
   }
@@ -463,15 +412,15 @@ class ZincWorkerImpl(
   }
 
   private def compileInternal(
-      upstreamCompileOutput: Seq[(os.Path, os.Path)],
+      upstreamCompileOutput: Seq[CompilationResult],
       sources: Agg[os.Path],
       compileClasspath: Agg[os.Path],
       javacOptions: Seq[String],
       scalacOptions: Seq[String],
       compilers: Compilers,
       reporter: Option[CompileProblemReporter],
       reportCachedProblems: Boolean
-  )(implicit ctx: ZincWorkerApi.Ctx): Result[(os.Path, os.Path)] = {
+  )(implicit ctx: ZincWorkerApi.Ctx): Result[CompilationResult] = {
     os.makeDir.all(ctx.dest)
 
     reporter.foreach(_.start())
@@ -512,7 +461,7 @@ class ZincWorkerImpl(
           }
         }
     }
-    val analysisMap0 = upstreamCompileOutput.map(_.swap).toMap
+    val analysisMap0 = upstreamCompileOutput.map(c => c.classes.path -> c.analysisFile).toMap
 
     def analysisMap(f: VirtualFile): Optional[CompileAnalysis] = {
       val analysisFile = f match {
@@ -615,7 +564,7 @@ class ZincWorkerImpl(
           newResult.setup()
         )
       )
-      Result.Success((zincFile, classesDir))
+      Result.Success(CompilationResult(zincFile, PathRef(classesDir)))
     } catch {
       case e: CompileFailed =>
         Result.Failure(e.toString)