Handle symbol.defTree properly for nested definitions in bindings

[liufengyun]

Handle symbol.defTree properly for nested definitions in bindings

Nested definitions in inlining bindings will get new symbols in
changeOwner. The Symbol.defTree is never set for those symbols.

The problem is exhibited in the following test

tests/pos/i10542.scala

The fix in 0f034aa works by accident:

@@ -115,7 +115,9 @@ class ReTyper extends Typer with ReChecking {
  }

  override def typedUnadapted(tree: untpd.Tree, pt: Type, locked: TypeVars)(using Context): Tree =
    try super.typedUnadapted(tree, pt, locked)
    try super.typedUnadapted(tree, pt, locked) match
      case member: MemberDef => member.setDefTree
      case tree => tree

The reason is the following:

• If we enable -Ycheck:all, it will sync the tree definition for
  all symbols during TreeChecker, thus no crash in initialization
  checker.

• if we disable -Ycheck:all, the defTree for <init> is not set,
  initialization checker ignore the method, thus no crash.

However, if we change InlineTyper instead of Retyper:

+    override def typedUnadapted(tree: untpd.Tree, pt: Type, locked: TypeVars)(using Context): Tree =
+      super.typedUnadapted(tree, pt, locked) match
+        case member: MemberDef => member.setDefTree
+        case tree => tree

There will be some mysterious behavior in compiling tests/pos/i10542.scala:

• Without -Ycheck:all, it succeeds
• With -Ycheck:all, the initialization check crashes due to missing
  defTree for the class $anon.

The reason for the mysterious behavior is the following:

• Without -Ycheck:all, there is no defTree for <init>,
  initialization check is skipped, thus no crash.

• With -Ycheck:all, the method Typer.typedDefDef will set
  Symbol.defTree for <init>, called from the TreeChecker, which
  extends Typer indirectly via ReTyper. However, in
  Typer.typedClassDef, we never set defTree for class symbols,
  thus the defTree for the class symbol $anon is empty, causing an
  exception in initialization check.

Co-authored-by: Nicolas Stucki [email protected]