additionally include writes under try/catch/finally

Author: olhotak

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

@@ -470,7 +470,7 @@ object Nullables:
                 else candidates -= name
               case None =>
             traverseChildren(tree)
-          case _: (If | WhileDo | Typed | Match | CaseDef) =>
+          case _: (If | WhileDo | Typed | Match | CaseDef | untpd.ParsedTry) =>
             traverseChildren(tree)      // assignments to candidate variables are OK here ...
           case _ =>
             reachable = Set.empty       // ... but not here

tests/explicit-nulls/pos/match-flow-typing.scala

@@ -6,3 +6,16 @@ def m(): String = {
   if(x == null) "foo"
   else x
 }
+
+def m2(): String = {
+  var x: String|Null = "foo"
+  try {
+    x = x
+  } catch {
+    case e => x = x
+  } finally {
+    x = x
+  }
+  if(x == null) "foo"
+  else x
+}