Turn on type-based avoidance

Author: Linyxus

compiler/src/dotty/tools/dotc/cc/CheckCaptures.scala

@@ -548,7 +548,7 @@ class CheckCaptures extends Recheck, SymTransformer:
           val included = cs.filter: c =>
             val isVisible = isVisibleFromEnv(c.pathOwner, env)
             if !isVisible then
-              if ccConfig.deferredReaches
+              if ccConfig.deferredReaches || ccConfig.caplessLike
               then avoidLocalCapability(c, env, lastEnv)
               else avoidLocalReachCapability(c, env)
             isVisible

tests/neg-custom-args/captures/capless-strawman3.check

@@ -0,0 +1,38 @@
+-- [E007] Type Mismatch Error: tests/neg-custom-args/captures/capless-strawman3.scala:5:23 ------------------------------
+5 |  val t2: () -> Unit = () => op()()  // error
+  |                       ^^^^^^^^^^^^
+  |               Found:    () ->{io1} Unit
+  |               Required: () -> Unit
+  |
+  |               Note that capability io1 is not included in capture set {}.
+  |
+  | longer explanation available when compiling with `-explain`
+-- [E007] Type Mismatch Error: tests/neg-custom-args/captures/capless-strawman3.scala:7:23 ------------------------------
+7 |  val t3: () -> Unit = () => op()()()  // error
+  |                       ^^^^^^^^^^^^^^
+  |               Found:    () ->{io1, io2} Unit
+  |               Required: () -> Unit
+  |
+  |               Note that capability io1 is not included in capture set {}.
+  |
+  | longer explanation available when compiling with `-explain`
+-- [E007] Type Mismatch Error: tests/neg-custom-args/captures/capless-strawman3.scala:8:29 ------------------------------
+8 |  val t3a: () ->{io2} Unit = () => op()()()  // error
+  |                             ^^^^^^^^^^^^^^
+  |            Found:    () ->{io1, io2} Unit
+  |            Required: () ->{io2} Unit
+  |
+  |            Note that capability io1 is not included in capture set {io2}.
+  |
+  | longer explanation available when compiling with `-explain`
+-- [E007] Type Mismatch Error: tests/neg-custom-args/captures/capless-strawman3.scala:11:23 -----------------------------
+11 |  val t1: () -> Unit = () =>  // error
+   |                       ^
+   |             Found:    () ->{io1} Unit
+   |             Required: () -> Unit
+   |
+   |             Note that capability io1 is not included in capture set {}.
+12 |    val f = op()
+13 |    f()
+   |
+   | longer explanation available when compiling with `-explain`

tests/neg-custom-args/captures/capless-strawman3.scala

@@ -0,0 +1,13 @@
+import language.experimental.captureChecking
+trait IO { def println(msg: String): Unit }
+def test1(io1: IO^, io2: IO^, op: () -> () ->{io1} () ->{io2} Unit): Unit =
+  val t1: () -> Unit = () => op()
+  val t2: () -> Unit = () => op()()  // error
+  val t2a: () ->{io1} Unit = () => op()()
+  val t3: () -> Unit = () => op()()()  // error
+  val t3a: () ->{io2} Unit = () => op()()()  // error
+  val t3b: () ->{io1, io2} Unit = () => op()()()
+def test2(io1: IO^, io2: IO^, op: () -> () ->{io1} () ->{io2} Unit): Unit =
+  val t1: () -> Unit = () =>  // error
+    val f = op()
+    f()