Avoid memory leaks on repeated compilation.

Several measures:

1. Invalidate classOfId and superIdOfClass in ContextBase after each run. These contain local classes
   that should become inaccessible.

2. Also clear implicitScope cache that maps types to their implicit scopes after each run. (not sure whether
   this is needed; it did show up in paths from root, but on second thought this might have been a gc-able
   cycle.

3. Avoid capturing contexts in lazy annotations.

4. Avoid capturing contexts in functions that compute souceModule and moduleClass

5. Avoid capturing contexts in Unpickler's postReadOp hook.

1 files changed, 4 insertions, 3 deletions

diff --git a/src/dotty/tools/dotc/core/SymbolLoaders.scala b/src/dotty/tools/dotc/core/SymbolLoaders.scala
index 6161d0e57..2484165f3 100644
--- a/src/dotty/tools/dotc/core/SymbolLoaders.scala
+++ b/src/dotty/tools/dotc/core/SymbolLoaders.scala
@@ -49,7 +49,7 @@ class SymbolLoaders {
       modFlags: FlagSet = EmptyFlags, clsFlags: FlagSet = EmptyFlags, scope: Scope = EmptyScope)(implicit ctx: Context): Symbol = {
     val module = ctx.newModuleSymbol(
       owner, name.toTermName, modFlags, clsFlags,
-      (modul, _) => completer.proxy withDecls newScope withSourceModule modul,
+      (module, _) => completer.proxy withDecls newScope withSourceModule (_ => module),
       assocFile = completer.sourceFileOrNull)
     enterNew(owner, module, completer, scope)
     enterNew(owner, module.moduleClass, completer, scope)
@@ -142,8 +142,9 @@ class SymbolLoaders {
 
   /** Load contents of a package
    */
-  class PackageLoader(override val sourceModule: TermSymbol, classpath: ClassPath)
+  class PackageLoader(_sourceModule: TermSymbol, classpath: ClassPath)
       extends SymbolLoader {
+    override def sourceModule(implicit ctx: Context) = _sourceModule
     def description = "package loader " + classpath.name
 
     private[core] val preDecls: MutableScope = newScope
@@ -242,7 +243,7 @@ class ClassfileLoader(val classfile: AbstractFile) extends SymbolLoader {
         else
           ctx.newModuleSymbol(
             rootDenot.owner, rootDenot.name.toTermName, Synthetic, Synthetic,
-            (module, _) => new NoCompleter() withDecls newScope withSourceModule module)
+            (module, _) => new NoCompleter() withDecls newScope withSourceModule (_ => module))
             .moduleClass.denot.asClass
     }
     if (rootDenot is ModuleClass) (linkedDenot, rootDenot)