Address review comments

Author: odersky

compiler/src/dotty/tools/dotc/config/Config.scala

@@ -161,7 +161,7 @@ object Config {
   final val showCompletions = false
 
   /** If set, enables tracing */
-  final val tracingEnabled = true
+  final val tracingEnabled = false
 
   /** Initial capacity of uniques HashMap.
    *  Note: This MUST BE a power of two to work with util.HashSet

docs/docs/reference/changed-features/overload-resolution.md

@@ -72,3 +72,13 @@ is determined as followed:
    of `E` is `(S_1, ..., S_n) => ?`, where each `S_i` is the type of parameter `p_i` if it is given, or `?`
    otherwise. Here `?` stands for a _wildcard type_ that is compatible with every other type.
  - Otherwise the known type of `E` is the result of typing `E` with an undefined expected type.
+
+A pattern matching closure
+```scala
+  { case P1 => B1 ... case P_n => B_n }
+````
+is treated as if it was expanded to the function value
+```scala
+  x => x match { case P1 => B1 ... case P_n => B_n }
+```
+and is therefore also approximated with a `? => ?` type.

tests/run/overloads.check

@@ -15,3 +15,4 @@ ok: M1.f(3) = 11
 ok: M2.f(3) = 22
 ok: M3.f("abc", _.reverse) = cba
 ok: M3.f(2, _ + 2) = 4
+ok: f("abc", { case s: String => s}) = abc

tests/run/overloads.scala

@@ -87,8 +87,8 @@ object overloads {
         check("M3.f(\"abc\", _.reverse)", M3.f("abc", _.reverse), "cba")
         check("M3.f(2, _ + 2)", M3.f(2, _ + 2), 4)
 
+        check("f(\"abc\", { case s: String => s})", M3.f("abc", { case s: String => s}), "abc")
     }
-
 }
 
 //############################################################################