Fix #877

src/dotty/tools/dotc/Compiler.scala

@@ -9,11 +9,10 @@ import Scopes._
 import typer.{FrontEnd, Typer, Mode, ImportInfo, RefChecks}
 import reporting.{Reporter, ConsoleReporter}
 import Phases.Phase
-import dotty.tools.dotc.transform._
-import dotty.tools.dotc.transform.TreeTransforms.{TreeTransform, TreeTransformer}
-import dotty.tools.dotc.core.DenotTransformers.DenotTransformer
-import dotty.tools.dotc.core.Denotations.SingleDenotation
-
+import transform._
+import transform.TreeTransforms.{TreeTransform, TreeTransformer}
+import core.DenotTransformers.DenotTransformer
+import core.Denotations.SingleDenotation
 
 import dotty.tools.backend.jvm.{LabelDefs, GenBCode}
 

src/dotty/tools/dotc/ast/Desugar.scala

@@ -132,7 +132,7 @@ object desugar {
       case tparam @ TypeDef(_, ContextBounds(tbounds, cxbounds)) =>
         for (cxbound <- cxbounds) {
           val paramFlags: FlagSet = if (isPrimaryConstructor) PrivateLocalParamAccessor else Param
-          val epname = (nme.EVIDENCE_PARAM_PREFIX.toString + epbuf.length).toTermName
+          val epname = ctx.freshName(nme.EVIDENCE_PARAM_PREFIX).toTermName
           epbuf += ValDef(epname, cxbound, EmptyTree).withFlags(paramFlags | Implicit)
         }
         cpy.TypeDef(tparam)(rhs = tbounds)

src/dotty/tools/dotc/core/Contexts.scala

@@ -153,6 +153,14 @@ object Contexts {
     protected def gadt_=(gadt: GADTMap) = _gadt = gadt
     def gadt: GADTMap = _gadt
 
+    /**The current fresh name creator */
+    private[this] var _freshNames: FreshNameCreator = _
+    protected def freshNames_=(freshNames: FreshNameCreator) = _freshNames = freshNames
+    def freshNames: FreshNameCreator = _freshNames
+
+    def freshName(prefix: String = ""): String = freshNames.newName(prefix)
+    def freshName(prefix: Name): String = freshName(prefix.toString)
+
     /** A map in which more contextual properties can be stored */
     private var _moreProperties: Map[String, Any] = _
     protected def moreProperties_=(moreProperties: Map[String, Any]) = _moreProperties = moreProperties
@@ -423,6 +431,7 @@ object Contexts {
     def setDiagnostics(diagnostics: Option[StringBuilder]): this.type = { this.diagnostics = diagnostics; this }
     def setTypeComparerFn(tcfn: Context => TypeComparer): this.type = { this.typeComparer = tcfn(this); this }
     def setSearchHistory(searchHistory: SearchHistory): this.type = { this.searchHistory = searchHistory; this }
+    def setFreshNames(freshNames: FreshNameCreator): this.type = { this.freshNames = freshNames; this }
     def setMoreProperties(moreProperties: Map[String, Any]): this.type = { this.moreProperties = moreProperties; this }
 
     def setProperty(prop: (String, Any)): this.type = setMoreProperties(moreProperties + prop)
@@ -468,6 +477,7 @@ object Contexts {
     typeAssigner = TypeAssigner
     runInfo = new RunInfo(this)
     diagnostics = None
+    freshNames = new FreshNameCreator.Default
     moreProperties = Map.empty
     typeComparer = new TypeComparer(this)
     searchHistory = new SearchHistory(0, Map())
@@ -498,12 +508,6 @@ object Contexts {
     /** The platform */
     val platform: Platform = new JavaPlatform
 
-    /** The standard fresh name creator */
-    val freshNames = new FreshNameCreator.Default
-
-    def freshName(prefix: String = ""): String = freshNames.newName(prefix)
-    def freshName(prefix: Name): String = freshName(prefix.toString)
-
     /** The loader that loads the members of _root_ */
     def rootLoader(root: TermSymbol)(implicit ctx: Context): SymbolLoader = platform.rootLoader(root)
 

src/dotty/tools/dotc/typer/FrontEnd.scala

@@ -9,6 +9,7 @@ import parsing.Parsers.Parser
 import config.Printers._
 import util.Stats._
 import scala.util.control.NonFatal
+import util.FreshNameCreator
 
 class FrontEnd extends Phase {
 
@@ -46,7 +47,8 @@ class FrontEnd extends Phase {
   }
 
   override def runOn(units: List[CompilationUnit])(implicit ctx: Context): List[CompilationUnit] = {
-    val unitContexts = units map (unit => ctx.fresh.setCompilationUnit(unit))
+    val unitContexts = for (unit <- units) yield
+      ctx.fresh.setCompilationUnit(unit).setFreshNames(new FreshNameCreator.Default)
     unitContexts foreach (parse(_))
     record("parsedTrees", ast.Trees.ntrees)
     unitContexts foreach (enterSyms(_))

tests/pos/i877.scala

@@ -0,0 +1,11 @@
+class First[A]
+class Second[A]
+
+class Foo {
+  def foo[A: First] = {
+    def bar[B: Second] = {
+      val fst: First[A] = implicitly[First[A]]
+      val snd: Second[B] = implicitly[Second[B]]
+    }
+  }
+}