Drop PostCapture

Instead narrow extractor for capturing types to yield results only at phase cc.

Author: odersky

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -87,7 +87,6 @@ class Compiler {
          new StringInterpolatorOpt) :: // Optimizes raw and s string interpolators by rewriting them to string concatenations
     List(new PreRecheck) ::          // Preparations for check captures phase, enabled under -Ycc
     List(new CheckCaptures) ::       // Check captures, enabled under -Ycc
-    List(new PostCapture) ::         // Reset denotations transformed by CheckCaptures back to annotated types
     List(new PruneErasedDefs,        // Drop erased definitions from scopes and simplify erased expressions
          new UninitializedDefs,      // Replaces `compiletime.uninitialized` by `_`
          new InlinePatterns,         // Remove placeholders of inlined patterns

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

@@ -11,12 +11,11 @@ object CapturingType:
     if refs.isAlwaysEmpty then parent
     else AnnotatedType(parent, CaptureAnnotation(refs))
 
-  def unapply(tp: AnnotatedType)(using Context) = tp.annot match
-    case ann: CaptureAnnotation =>
-      Some((tp.parent, ann.refs))
-    case ann =>
-      if ann.symbol == defn.RetainsAnnot && ctx.phase == Phases.checkCapturesPhase
-      then Some((tp.parent, ann.tree.toCaptureSet))
-      else None
+  def unapply(tp: AnnotatedType)(using Context) =
+    if ctx.phase == Phases.checkCapturesPhase && tp.annot.symbol == defn.RetainsAnnot then
+      tp.annot match
+        case ann: CaptureAnnotation => Some((tp.parent, ann.refs))
+        case ann => Some((tp.parent, ann.tree.toCaptureSet))
+    else None
 
 end CapturingType

compiler/src/dotty/tools/dotc/transform/EmptyPhase.scala

@@ -0,0 +1,19 @@
+package dotty.tools.dotc
+package transform
+
+import core.*
+import Contexts.Context
+import Phases.Phase
+
+/** A phase that can be inserted directly after a phase that cannot
+ *  be checked, to enable a -Ycheck as soon as possible afterwards
+ */
+class EmptyPhase extends Phase:
+
+  def phaseName: String = "dummy"
+
+  override def isEnabled(using Context) = prev.isEnabled
+
+  override def run(using Context) = ()
+
+end EmptyPhase