From 8ab5f002cc4bf1059f8f4241350ae7206d65f221 Mon Sep 17 00:00:00 2001
From: Liu Fengyun <liu@fengy.me>
Date: Fri, 26 Feb 2021 23:11:41 +0100
Subject: [PATCH] Handle symbol.defTree properly for nested definitions in
 bindings

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

The problem is exhibited in the following test

    tests/pos/i10542.scala

The fix in 0f034aa0b51ca7df6cdff54b5a3066b0df6465b8 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 ignores 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 <nicolas.stucki@gmail.com>
---
 compiler/src/dotty/tools/dotc/typer/Inliner.scala | 15 ++++++++++++---
 compiler/src/dotty/tools/dotc/typer/ReTyper.scala |  4 +---
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/typer/Inliner.scala b/compiler/src/dotty/tools/dotc/typer/Inliner.scala
index d89ba6128274..1f89c8e7337a 100644
--- a/compiler/src/dotty/tools/dotc/typer/Inliner.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Inliner.scala
@@ -464,7 +464,7 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(using Context) {
       if (isByName) DefDef(boundSym, arg.changeOwner(ctx.owner, boundSym))
       else ValDef(boundSym, arg)
     }.withSpan(boundSym.span)
-    bindingsBuf += binding.setDefTree
+    bindingsBuf += binding
     binding
   }
 
@@ -521,7 +521,7 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(using Context) {
           ref(rhsClsSym.sourceModule)
         else
           inlineCallPrefix
-      val binding = ValDef(selfSym.asTerm, QuoteUtils.changeOwnerOfTree(rhs, selfSym)).withSpan(selfSym.span).setDefTree
+      val binding = ValDef(selfSym.asTerm, QuoteUtils.changeOwnerOfTree(rhs, selfSym)).withSpan(selfSym.span)
       bindingsBuf += binding
       inlining.println(i"proxy at $level: $selfSym = ${bindingsBuf.last}")
       lastSelf = selfSym
@@ -797,7 +797,12 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(using Context) {
       bindingsBuf.mapInPlace { binding =>
         // Set trees to symbols allow macros to see the definition tree.
         // This is used by `underlyingArgument`.
-        reducer.normalizeBinding(binding)(using inlineCtx).setDefTree
+        val binding1 = reducer.normalizeBinding(binding)(using inlineCtx).setDefTree
+        binding1.foreachSubTree {
+          case tree: MemberDef => tree.setDefTree
+          case _ =>
+        }
+        binding1
       }
 
       // Run a typing pass over the inlined tree. See InlineTyper for details.
@@ -1382,6 +1387,10 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(using Context) {
       if Inliner.needsInlining(tree) then Inliner.inlineCall(tree)
       else tree
 
+    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
   }
 
   /** Drop any side-effect-free bindings that are unused in expansion or other reachable bindings.
diff --git a/compiler/src/dotty/tools/dotc/typer/ReTyper.scala b/compiler/src/dotty/tools/dotc/typer/ReTyper.scala
index 42c71c1a7b72..8ff0dfc8c61b 100644
--- a/compiler/src/dotty/tools/dotc/typer/ReTyper.scala
+++ b/compiler/src/dotty/tools/dotc/typer/ReTyper.scala
@@ -115,9 +115,7 @@ 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) match
-      case member: MemberDef => member.setDefTree
-      case tree => tree
+    try super.typedUnadapted(tree, pt, locked)
     catch {
       case NonFatal(ex) =>
         if ctx.phase != Phases.typerPhase && ctx.phase != Phases.inliningPhase then