Tighten rules against escaping local references

Fixes the problem in effect-swaps.scala
scala · Jun 13, 2024 · 5571b5c · 5571b5c
1 parent 27a3f80
commit 5571b5c
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Showing 4 changed files with 11 additions and 7 deletions.
diff --git a/compiler/src/dotty/tools/dotc/cc/CheckCaptures.scala b/compiler/src/dotty/tools/dotc/cc/CheckCaptures.scala
@@ -1078,7 +1078,9 @@ class CheckCaptures extends Recheck, SymTransformer:
     /** If actual derives from caps.Capability, yet is not a capturing type itself,
      *  make its capture set explicit.
      */
-    private def makeCaptureSetExplicit(actual: Type)(using Context): Type = actual match
+    private def makeCaptureSetExplicit(actual: Type)(using Context): Type =
+      if false then actual
+      else actual match
       case CapturingType(_, _) => actual
       case _ if actual.derivesFromCapability =>
         val cap: CaptureRef = actual match
@@ -1284,7 +1286,7 @@ class CheckCaptures extends Recheck, SymTransformer:
                 case ref: TermParamRef
                 if !allowed.contains(ref) && !seen.contains(ref) =>
                   seen += ref
-                  if ref.underlying.isRef(defn.Caps_Capability) then
+                  if ref.isMaxCapability then
                     report.error(i"escaping local reference $ref", tree.srcPos)
                   else
                     val widened = ref.captureSetOfInfo

diff --git a/compiler/src/dotty/tools/dotc/cc/Setup.scala b/compiler/src/dotty/tools/dotc/cc/Setup.scala
@@ -575,10 +575,8 @@ class Setup extends PreRecheck, SymTransformer, SetupAPI:
         !refs.isEmpty
       case tp: (TypeRef | AppliedType) =>
         val sym = tp.typeSymbol
-        if sym.isClass then
-          !sym.isPureClass
-        else
-          sym != defn.Caps_Capability && instanceCanBeImpure(tp.superType)
+        if sym.isClass then !sym.isPureClass
+        else instanceCanBeImpure(tp.superType)
       case tp: (RefinedOrRecType | MatchType) =>
         instanceCanBeImpure(tp.underlying)
       case tp: AndType =>

diff --git a/tests/neg-custom-args/captures/effect-swaps.check b/tests/neg-custom-args/captures/effect-swaps.check
@@ -22,3 +22,7 @@
 73 |            fr.await.ok
    |
    | longer explanation available when compiling with `-explain`
+-- Error: tests/neg-custom-args/captures/effect-swaps.scala:66:15 ------------------------------------------------------
+66 |        Result.make: // error
+   |        ^^^^^^^^^^^
+   |        escaping local reference contextual$9.type
diff --git a/tests/neg-custom-args/captures/effect-swaps.scala b/tests/neg-custom-args/captures/effect-swaps.scala
@@ -63,7 +63,7 @@ def test[T, E](using Async) =
           fr.await.ok
 
     def fail4[T, E](fr: Future[Result[T, E]]^) =
-        Result.make: //lbl ?=> // should be error, escaping label from Result but infers Result[Any, Any]
+        Result.make: // error
           Future: fut ?=>
             fr.await.ok