Avoid memory leaks in InlineAccessors

Make sure that `AccessProxies.accessedBy` can be GCed.

Author: nicolasstucki

compiler/src/dotty/tools/dotc/CompilationUnit.scala

@@ -56,9 +56,6 @@ class CompilationUnit protected (val source: SourceFile) {
    */
   var needsQuotePickling: Boolean = false
 
-  /** A structure containing a temporary map for generating inline accessors */
-  val inlineAccessors: InlineAccessors = new InlineAccessors
-
   var suspended: Boolean = false
   var suspendedAtInliningPhase: Boolean = false
 

compiler/src/dotty/tools/dotc/transform/Inlining.scala

@@ -15,6 +15,7 @@ import SymUtils._
 import NameKinds._
 import dotty.tools.dotc.ast.tpd
 import typer.Implicits.SearchFailureType
+import typer.PrepareInlineable
 
 import scala.collection.mutable
 import dotty.tools.dotc.core.Annotations._

compiler/src/dotty/tools/dotc/typer/PrepareInlineable.scala

@@ -26,6 +26,19 @@ import dotty.tools.dotc.transform.TreeMapWithStages._
 object PrepareInlineable {
   import tpd._
 
+  private val InlineAccessorsKey = new Property.Key[InlineAccessors]
+
+  def initContext(ctx: Context): Context =
+    ctx.fresh.setProperty(InlineAccessorsKey, new InlineAccessors)
+
+  def makeInlineable(tree: Tree)(using Context): Tree =
+    ctx.property(InlineAccessorsKey).get.makeInlineable(tree)
+
+  def addAccessorDefs(cls: Symbol, body: List[Tree])(using Context): List[Tree] =
+    ctx.property(InlineAccessorsKey) match
+      case Some(inlineAccessors) => inlineAccessors.addAccessorDefs(cls, body)
+      case _ => body
+
   class InlineAccessors extends AccessProxies {
 
     /** If an inline accessor name wraps a unique inline name, this is taken as indication
@@ -251,7 +264,7 @@ object PrepareInlineable {
             if inlined.isInlineMethod then
               inlinedBody = dropInlineIfError(inlined,
                 checkInlineMethod(inlined,
-                  ctx.compilationUnit.inlineAccessors.makeInlineable(inlinedBody)))
+                  PrepareInlineable.makeInlineable(inlinedBody)))
             inlining.println(i"Body to inline for $inlined: $inlinedBody")
             inlinedBody
           })

compiler/src/dotty/tools/dotc/typer/QuotesAndSplices.scala

@@ -70,7 +70,7 @@ trait QuotesAndSplices {
   }
 
   private def makeInlineable(tree: Tree)(using Context): Tree =
-    ctx.compilationUnit.inlineAccessors.makeInlineable(tree)
+    PrepareInlineable.makeInlineable(tree)
 
   /** Translate `${ t: Expr[T] }` into expression `t.splice` while tracking the quotation level in the context */
   def typedSplice(tree: untpd.Splice, pt: Type)(using Context): Tree = {

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -2461,7 +2461,7 @@ class Typer extends Namer
       // 4. Polymorphic type defs override nothing.
 
   protected def addAccessorDefs(cls: Symbol, body: List[Tree])(using Context): List[Tree] =
-    ctx.compilationUnit.inlineAccessors.addAccessorDefs(cls, body)
+    PrepareInlineable.addAccessorDefs(cls, body)
 
   /** If this is a real class, make sure its first parent is a
    *  constructor call. Cannot simply use a type. Overridden in ReTyper.

compiler/src/dotty/tools/dotc/typer/TyperPhase.scala

@@ -81,7 +81,8 @@ class TyperPhase(addRootImports: Boolean = true) extends Phase {
   override def runOn(units: List[CompilationUnit])(using Context): List[CompilationUnit] =
     val unitContexts =
       for unit <- units yield
-        val newCtx = ctx.fresh.setPhase(this.start).setCompilationUnit(unit)
+        val newCtx0 = ctx.fresh.setPhase(this.start).setCompilationUnit(unit)
+        val newCtx = PrepareInlineable.initContext(newCtx0)
         report.inform(s"typing ${unit.source}")
         if (addRootImports)
           newCtx.withRootImports