Make sure we don't recheck closure bodies twice (#23066)

Author: noti0na1

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

@@ -949,7 +949,12 @@ class CheckCaptures extends Recheck, SymTransformer:
         // TODO follow up on this
       try
         matchParams(mdef.paramss, pt)
-        recheckDef(mdef, mdef.symbol)
+        capt.println(i"recheck closure block $mdef: ${mdef.symbol.infoOrCompleter}")
+        if !mdef.symbol.isCompleted then
+          mdef.symbol.ensureCompleted() // this will recheck def
+        else
+          recheckDef(mdef, mdef.symbol)
+
         recheckClosure(expr, pt, forceDependent = true)
       finally
         openClosures = openClosures.tail
@@ -1112,6 +1117,10 @@ class CheckCaptures extends Recheck, SymTransformer:
       finally
         curEnv = saved
 
+    override def recheckTypeDef(tree: TypeDef, sym: Symbol)(using Context): Type =
+      try super.recheckTypeDef(tree, sym)
+      finally completed += sym
+
     /** Recheck classDef by enforcing the following class-specific capture set relations:
      *   1. The capture set of a class includes the capture sets of its parents.
      *   2. The capture set of the self type of a class includes the capture set of the class.
@@ -1156,6 +1165,7 @@ class CheckCaptures extends Recheck, SymTransformer:
         ccState.inNestedLevelUnless(cls.is(Module)):
           super.recheckClassDef(tree, impl, cls)
       finally
+        completed += cls
         curEnv = saved
 
     /** If type is of the form `T @requiresCapability(x)`,

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

@@ -524,12 +524,14 @@ abstract class Recheck extends Phase, SymTransformer:
               if !skipRecheck(sym) then recheckDef(tree, sym)
               sym.termRef
           case tree: TypeDef =>
-            // TODO: Should we allow for completers as for ValDefs or DefDefs?
-            tree.rhs match
-              case impl: Template =>
-                recheckClassDef(tree, impl, sym.asClass)(using ctx.localContext(tree, sym))
-              case _ =>
-                recheckTypeDef(tree, sym)(using ctx.localContext(tree, sym))
+            if !skipRecheck(sym) then
+              // TODO: Should we allow for completers as for ValDefs or DefDefs?
+              tree.rhs match
+                case impl: Template =>
+                  recheckClassDef(tree, impl, sym.asClass)(using ctx.localContext(tree, sym))
+                case _ =>
+                  recheckTypeDef(tree, sym)(using ctx.localContext(tree, sym))
+            sym.typeRef
           case tree: Labeled => recheckLabeled(tree, pt)
 
       def recheckUnnamed(tree: Tree, pt: Type): Type = tree match