Allow casting borrowed to unmanaged (chapel-lang#24356)

This PR partially reverts the 1.31 deprecation of casting to
`unmanaged`. Prior to the deprecation, any managed class object could be
casted to an `unmanaged` instance without affecting the lifetime of the
original object. The cast was only allowed for `borrowed` to
`unmanaged`, but implicit conversion allowed casting `owned` or `shared`
to `unmanaged`. After this PR, users can only cast explicit `borrowed`
objects to `unmanaged`. This allows users to escape the lifetime
checker.

This PR also reverts some of the changes chapel-lang#22404 made to the packaged
modules and tests.

Testing
- [x] paratest w/wo comm
- [x] built and checked docs

Note to reviewer: since the cast to `unmanaged` has been deprecated for
3 releases, this PR adding a new error message moved straight to making
it an error rather than a deprecation warning that will become an error
in the future.

[Reviewed by @lydia-duncan]

closes chapel-lang#23731

modules/dists/BlockDist.chpl

@@ -837,7 +837,7 @@ override proc BlockImpl.dsiNewRectangularDom(param rank: int, type idxType,
   delete dummyLBD;
 
   var dom = new unmanaged BlockDom(rank, idxType, strides, sparseLayoutType,
-                                   _to_unmanaged(this), locDomsTemp, whole);
+                                   this:unmanaged, locDomsTemp, whole);
 
   if debugBlockDist {
     writeln("Creating new Block domain:");

modules/dists/CyclicDist.chpl

@@ -553,7 +553,7 @@ override proc CyclicImpl.dsiNewRectangularDom(param rank: int, type idxType, par
   delete dummyLCD;
 
   var dom = new unmanaged CyclicDom(rank, idxType, strides,
-                                    _to_unmanaged(this), locDomsTemp, whole);
+                                    this:unmanaged, locDomsTemp, whole);
   return dom;
 }
 

modules/internal/ChapelBase.chpl

@@ -2220,46 +2220,59 @@ module ChapelBase {
     compilerError("cannot cast nil to " + t:string);
   }
 
+  proc chpl_castUnmanagedError(param typeStr: string) param do
+    compilerError("cannot cast to a '" + typeStr +
+                  "' with an implicit borrow; try adding an explicit '.borrow()'");
+
+
+  pragma "last resort"
+  operator :(x:owned class, type t:unmanaged class)
+    do chpl_castUnmanagedError(t:string);
+  pragma "last resort"
+  operator :(x:owned class?, type t:unmanaged class)
+    do chpl_castUnmanagedError(t:string);
+  pragma "last resort"
+  operator :(x:owned class, type t:unmanaged class?)
+    do chpl_castUnmanagedError(t:string);
+  pragma "last resort"
+  operator :(x:owned class?, type t:unmanaged class?)
+    do chpl_castUnmanagedError(t:string);
+
+  pragma "last resort"
+  operator :(x:shared class, type t:unmanaged class)
+    do chpl_castUnmanagedError(t:string);
+  pragma "last resort"
+  operator :(x:shared class?, type t:unmanaged class)
+    do chpl_castUnmanagedError(t:string);
+  pragma "last resort"
+  operator :(x:shared class, type t:unmanaged class?)
+    do chpl_castUnmanagedError(t:string);
+  pragma "last resort"
+  operator :(x:shared class?, type t:unmanaged class?)
+    do chpl_castUnmanagedError(t:string);
+
   // casting to unmanaged?, no class downcast
   pragma "last resort"
-  @deprecated("casting from a managed class to an 'unmanaged?' is deprecated")
   inline operator :(x:borrowed class?, type t:unmanaged class?)
     where isSubtype(_to_unmanaged(x.type),t)
   {
     return __primitive("cast", t, x);
   }
-  inline operator :(x:unmanaged class?, type t:unmanaged class?)
-    where isSubtype(_to_unmanaged(x.type),t)
-  {
-    return __primitive("cast", t, x);
-  }
 
   pragma "last resort"
-  @deprecated("casting from a managed class to an 'unmanaged?' is deprecated")
   inline operator :(x:borrowed class, type t:unmanaged class?)
     where isSubtype(_to_nonnil(_to_unmanaged(x.type)),t)
   {
     return __primitive("cast", t, x);
   }
-  inline operator :(x:unmanaged class, type t:unmanaged class?)
-    where isSubtype(_to_nonnil(_to_unmanaged(x.type)),t)
-  {
-    return __primitive("cast", t, x);
-  }
 
   // casting to unmanaged, no class downcast
   pragma "last resort"
-  @deprecated("casting from a managed class to an 'unmanaged' is deprecated")
   inline operator :(x:borrowed class, type t:unmanaged class)
     where isSubtype(_to_unmanaged(x.type),t)
   {
     return __primitive("cast", t, x);
   }
-  inline operator :(x:unmanaged class, type t:unmanaged class)
-    where isSubtype(_to_unmanaged(x.type),t)
-  {
-    return __primitive("cast", t, x);
-  }
 
   // casting away nilability, no class downcast
   inline operator :(x:unmanaged class?, type t:borrowed class) throws
@@ -2284,7 +2297,6 @@ module ChapelBase {
 
   // casting away nilability, no class downcast
   pragma "last resort"
-  @deprecated("casting from a managed class to an 'unmanaged' is deprecated")
   inline operator :(x:borrowed class?, type t:unmanaged class)  throws
     where isSubtype(_to_nonnil(_to_unmanaged(x.type)),t)
   {
@@ -2293,14 +2305,6 @@ module ChapelBase {
     }
     return __primitive("cast", t, x);
   }
-  inline operator :(x:unmanaged class?, type t:unmanaged class)  throws
-    where isSubtype(_to_nonnil(_to_unmanaged(x.type)),t)
-  {
-    if x == nil {
-      throw new owned NilClassError();
-    }
-    return __primitive("cast", t, x);
-  }
 
   // this version handles downcast to non-nil borrowed
   inline operator :(x:borrowed class?, type t:borrowed class)  throws
@@ -2331,7 +2335,6 @@ module ChapelBase {
 
   // this version handles downcast to non-nil unmanaged
   pragma "last resort"
-  @deprecated("casting from a managed class to an 'unmanaged' is deprecated")
   inline operator :(x:borrowed class?, type t:unmanaged class) throws
     where isProperSubtype(t,_to_nonnil(_to_unmanaged(x.type)))
   {
@@ -2345,23 +2348,9 @@ module ChapelBase {
 
     return _to_nonnil(_to_unmanaged(tmp));
   }
-  inline operator :(x:unmanaged class?, type t:unmanaged class) throws
-    where isProperSubtype(t,_to_nonnil(_to_unmanaged(x.type)))
-  {
-    if x == nil {
-      throw new owned NilClassError();
-    }
-    var tmp = __primitive("dynamic_cast", t, x);
-    if tmp == nil {
-      throw new owned ClassCastError();
-    }
-
-    return _to_nonnil(_to_unmanaged(tmp));
-  }
 
   // this version handles downcast to nilable unmanaged
   pragma "last resort"
-  @deprecated("casting from a managed class to an 'unmanaged?' is deprecated")
   inline operator :(x:borrowed class?, type t:unmanaged class?)
     where isProperSubtype(t,_to_unmanaged(x.type))
   {
@@ -2371,19 +2360,9 @@ module ChapelBase {
     var tmp = __primitive("dynamic_cast", t, x);
     return _to_nilable(_to_unmanaged(tmp));
   }
-  inline operator :(x:unmanaged class?, type t:unmanaged class?)
-    where isProperSubtype(t,_to_unmanaged(x.type))
-  {
-    if x == nil {
-      return nil;
-    }
-    var tmp = __primitive("dynamic_cast", t, x);
-    return _to_nilable(_to_unmanaged(tmp));
-  }
 
   // this version handles downcast to nilable unmanaged
   pragma "last resort"
-  @deprecated("casting from a managed class to an 'unmanaged?' is deprecated")
   inline operator :(x:borrowed class, type t:unmanaged class?)
     where isProperSubtype(_to_nonnil(_to_borrowed(t)),x.type)
   {
@@ -2393,15 +2372,6 @@ module ChapelBase {
     var tmp = __primitive("dynamic_cast", t, x);
     return _to_nilable(_to_unmanaged(tmp));
   }
-  inline operator :(x:unmanaged class, type t:unmanaged class?)
-    where isProperSubtype(_to_nonnil(_to_borrowed(t)),x.type)
-  {
-    if x == nil {
-      return nil;
-    }
-    var tmp = __primitive("dynamic_cast", t, x);
-    return _to_nilable(_to_unmanaged(tmp));
-  }
 
 
 

modules/internal/DefaultAssociative.chpl

@@ -98,7 +98,7 @@ module DefaultAssociative {
 
       // set the rehash helpers
       this.table.rehashHelpers =
-        new DefaultAssociativeDomRehashHelper(_to_unmanaged(this));
+        new DefaultAssociativeDomRehashHelper(this:unmanaged);
     }
     proc deinit() {
       // chpl__hashtable.deinit does all we need here
@@ -111,7 +111,7 @@ module DefaultAssociative {
       return new unmanaged DefaultAssociativeArr(eltType=eltType,
                                                  idxType=idxType,
                                                  parSafeDom=parSafe,
-                                                 dom=_to_unmanaged(this),
+                                                 dom=this:unmanaged,
                                                  initElts=initElts);
     }
 
@@ -448,7 +448,7 @@ module DefaultAssociative {
 
     proc dsiLocalSubdomain(loc: locale) {
       if this.locale == loc {
-        return _getDomain(_to_unmanaged(this));
+        return _getDomain(this:unmanaged);
       } else {
         var a: domain(idxType, parSafe=parSafe);
         return a;

modules/internal/OwnedObject.chpl

@@ -411,7 +411,7 @@ module OwnedObject {
   @chpldoc.nodoc
   inline operator :(pragma "nil from arg" in x:owned class, type t:owned class?)    where isSubtype(x.chpl_t,_to_nonnil(t.chpl_t))
   {
-    var castPtr = _to_unmanaged(x.chpl_p):_to_nilable(_to_unmanaged(t.chpl_t));
+    var castPtr = x.chpl_p:_to_nilable(_to_unmanaged(t.chpl_t));
     x.chpl_p = nil;
     // t stores a nilable type
     return new _owned(castPtr);
@@ -422,7 +422,7 @@ module OwnedObject {
   inline operator :(pragma "nil from arg" in x:owned class?, type t:owned class?)
     where isSubtype(x.chpl_t,t.chpl_t)
   {
-    var castPtr = _to_unmanaged(x.chpl_p):_to_nilable(_to_unmanaged(t.chpl_t));
+    var castPtr = x.chpl_p:_to_nilable(_to_unmanaged(t.chpl_t));
     x.chpl_p = nil;
     // t stores a nilable type
     return new _owned(castPtr);
@@ -433,7 +433,7 @@ module OwnedObject {
   inline operator :(pragma "nil from arg" in x:owned class, type t:owned class)
     where isSubtype(x.chpl_t,t.chpl_t)
   {
-    var castPtr = _to_unmanaged(x.chpl_p):_to_nilable(_to_unmanaged(t.chpl_t));
+    var castPtr = x.chpl_p:_to_nilable(_to_unmanaged(t.chpl_t));
     x.chpl_p = nil;
     // t stores a non-nilable type
     return new _owned(castPtr!);
@@ -444,7 +444,7 @@ module OwnedObject {
   inline operator :(in x:owned class?, type t:owned class) throws
     where isSubtype(_to_nonnil(x.chpl_t),t.chpl_t)
   {
-    var castPtr = _to_unmanaged(x.chpl_p):_to_nilable(_to_unmanaged(t.chpl_t));
+    var castPtr = x.chpl_p:_to_nilable(_to_unmanaged(t.chpl_t));
     if castPtr == nil {
       throw new owned NilClassError();
     }
@@ -462,7 +462,7 @@ module OwnedObject {
       throw new owned NilClassError();
     }
     // the following line can throw ClassCastError
-    var castPtr = try _to_unmanaged(x.chpl_p):_to_nonnil(_to_unmanaged(t.chpl_t));
+    var castPtr = try x.chpl_p:_to_nonnil(_to_unmanaged(t.chpl_t));
     x.chpl_p = nil;
     return new _owned(castPtr);
   }
@@ -471,7 +471,7 @@ module OwnedObject {
     where isProperSubtype(t.chpl_t,x.chpl_t)
   {
     // the following line can throw ClassCastError
-    var castPtr = try _to_unmanaged(x.chpl_p):_to_nonnil(_to_unmanaged(t.chpl_t));
+    var castPtr = try x.chpl_p:_to_nonnil(_to_unmanaged(t.chpl_t));
     x.chpl_p = nil;
     return new _owned(castPtr);
   }
@@ -483,7 +483,7 @@ module OwnedObject {
     where isProperSubtype(t.chpl_t,x.chpl_t)
   {
     // this cast returns nil if the dynamic type is not compatible
-    var castPtr = _to_unmanaged(x.chpl_p):_to_nilable(_to_unmanaged(t.chpl_t));
+    var castPtr = x.chpl_p:_to_nilable(_to_unmanaged(t.chpl_t));
     if castPtr != nil {
       x.chpl_p = nil;
     }
@@ -495,7 +495,7 @@ module OwnedObject {
     where isProperSubtype(_to_nonnil(t.chpl_t),x.chpl_t)
   {
     // this cast returns nil if the dynamic type is not compatible
-    var castPtr = _to_unmanaged(x.chpl_p):_to_nilable(_to_unmanaged(t.chpl_t));
+    var castPtr = x.chpl_p:_to_nilable(_to_unmanaged(t.chpl_t));
     if castPtr != nil {
       x.chpl_p = nil;
     }

modules/internal/SharedObject.chpl

@@ -635,7 +635,7 @@ module SharedObject {
       throw new owned NilClassError();
     }
     // the following line can throw ClassCastError
-    var p = try _to_unmanaged(x.chpl_p):_to_nonnil(_to_unmanaged(t.chpl_t));
+    var p = try x.chpl_p:_to_nonnil(_to_unmanaged(t.chpl_t));
 
     return new _shared(true, _to_borrowed(p.type), p, x.chpl_pn);
   }
@@ -644,7 +644,7 @@ module SharedObject {
     where isProperSubtype(t.chpl_t, x.chpl_t)
   {
     // the following line can throw ClassCastError
-    var p = try _to_unmanaged(x.chpl_p):_to_nonnil(_to_unmanaged(t.chpl_t));
+    var p = try x.chpl_p:_to_nonnil(_to_unmanaged(t.chpl_t));
 
     return new _shared(true, _to_borrowed(p.type), p, x.chpl_pn);
   }
@@ -656,15 +656,15 @@ module SharedObject {
     where isProperSubtype(t.chpl_t, x.chpl_t)
   {
     // this cast returns nil if the dynamic type is not compatible
-    var p = _to_unmanaged(x.chpl_p):_to_nilable(_to_unmanaged(t.chpl_t));
+    var p = x.chpl_p:_to_nilable(_to_unmanaged(t.chpl_t));
     return new _shared(true, _to_borrowed(p.type), p, x.chpl_pn);
   }
   @chpldoc.nodoc
   inline operator :(const ref x:shared class, type t:shared class?)
     where isProperSubtype(t.chpl_t, x.chpl_t:class?)
   {
     // this cast returns nil if the dynamic type is not compatible
-    var p = _to_unmanaged(x.chpl_p):_to_nilable(_to_unmanaged(t.chpl_t));
+    var p = x.chpl_p:_to_nilable(_to_unmanaged(t.chpl_t));
     return new _shared(true, _to_borrowed(p.type), p, x.chpl_pn);
   }
 

modules/packages/Curl.chpl

@@ -533,7 +533,7 @@ module Curl {
                           end:int(64),
                           qioChannelPtr:qio_channel_ptr_t):errorCode {
         var curlch = new unmanaged CurlChannel();
-        curlch.curlf = _to_unmanaged(this);
+        curlch.curlf = this:unmanaged;
         curlch.qio_ch = qioChannelPtr;
         pluginChannel = curlch;
         return start_channel(curlch, start, end);

modules/packages/EpochManager.chpl

@@ -608,7 +608,7 @@ module EpochManager {
       }
       tok!.is_registered.write(true);
       // return tok;
-      return new owned TokenWrapper(tok!, _to_unmanaged(this));
+      return new owned TokenWrapper(tok!, this:unmanaged);
     }
 
     @chpldoc.nodoc
@@ -936,7 +936,7 @@ module EpochManager {
       }
       tok!.is_registered.write(true);
       // return tok;
-      return new owned DistTokenWrapper(tok!, _to_unmanaged(this));
+      return new owned DistTokenWrapper(tok!, this:unmanaged);
     }
 
     @chpldoc.nodoc

modules/packages/HDFS.chpl

@@ -346,7 +346,7 @@ module HDFS {
 
       // Create an HDFSFile and return the QIO file containing it
       // this initializer bumps the reference count to this
-      var fl = new unmanaged HDFSFile(_to_unmanaged(this), hfile, path);
+      var fl = new unmanaged HDFSFile(this:unmanaged, hfile, path);
 
       var ret: file;
       try {
@@ -387,7 +387,7 @@ module HDFS {
       if verbose then
         writeln("HDFSFile.setupChannel");
 
-      var hdfsch = new unmanaged HDFSChannel(_to_unmanaged(this), qioChannelPtr);
+      var hdfsch = new unmanaged HDFSChannel(this:unmanaged, qioChannelPtr);
       pluginChannel = hdfsch;
       return 0;
     }