add compilation for [nextto] and [yieldto]; fix [a90d9331bc]

10 files changed, 317 insertions, 43 deletions

diff --git a/generic/tclAssembly.c b/generic/tclAssembly.c
index 89c286a..7b775a9 100644
--- a/generic/tclAssembly.c
+++ b/generic/tclAssembly.c
@@ -26,6 +26,7 @@
  *-   jumpTable testing
  *-   syntax (?)
  *-   returnCodeBranch
+ *-   tclooNext, tclooNextClass
  */
 
 #include "tclInt.h"
diff --git a/generic/tclBasic.c b/generic/tclBasic.c
index 7c02706..cb9428c 100644
--- a/generic/tclBasic.c
+++ b/generic/tclBasic.c
@@ -259,7 +259,7 @@ static const CmdInfo builtInCmds[] = {
     {"variable",	Tcl_VariableObjCmd,	TclCompileVariableCmd,	NULL,	CMD_IS_SAFE},
     {"while",		Tcl_WhileObjCmd,	TclCompileWhileCmd,	TclNRWhileObjCmd,	CMD_IS_SAFE},
     {"yield",		NULL,			TclCompileYieldCmd,	TclNRYieldObjCmd,	CMD_IS_SAFE},
-    {"yieldto",		NULL,			NULL,			TclNRYieldToObjCmd,	CMD_IS_SAFE},
+    {"yieldto",		NULL,			TclCompileYieldToCmd,	TclNRYieldToObjCmd,	CMD_IS_SAFE},
 
     /*
      * Commands in the OS-interface. Note that many of these are unsafe.
@@ -8431,11 +8431,13 @@ TclNRYieldToObjCmd(
 	return TCL_ERROR;
     }
 
-    /*
-     * Add the tailcall in the caller env, then just yield.
-     *
-     * This is essentially code from TclNRTailcallObjCmd
-     */
+    if (((Namespace *) TclGetCurrentNamespace(interp))->flags & NS_DYING) {
+        Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		"yieldto called in deleted namespace", -1));
+        Tcl_SetErrorCode(interp, "TCL", "COROUTINE", "YIELDTO_IN_DELETED",
+		NULL);
+        return TCL_ERROR;
+    }
 
     /*
      * Add the tailcall in the caller env, then just yield.
@@ -8444,15 +8446,9 @@ TclNRYieldToObjCmd(
      */
 
     listPtr = Tcl_NewListObj(objc, objv);
-
     nsObjPtr = Tcl_NewStringObj(nsPtr->fullName, -1);
-    if ((TCL_OK != TclGetNamespaceFromObj(interp, nsObjPtr, &ns1Ptr))
-	    || (nsPtr != ns1Ptr)) {
-	Tcl_Panic("yieldto failed to find the proper namespace");
-    }
     TclListObjSetElement(interp, listPtr, 0, nsObjPtr);
 
-
     /*
      * Add the callback in the caller's env, then instruct TEBC to yield.
      */
diff --git a/generic/tclCompCmdsGR.c b/generic/tclCompCmdsGR.c
index b8a7e0f..b3e273f 100644
--- a/generic/tclCompCmdsGR.c
+++ b/generic/tclCompCmdsGR.c
@@ -3075,6 +3075,31 @@ TclCompileObjectNextCmd(
 }
 
 int
+TclCompileObjectNextToCmd(
+    Tcl_Interp *interp,		/* Used for error reporting. */
+    Tcl_Parse *parsePtr,	/* Points to a parse structure for the command
+				 * created by Tcl_ParseCommand. */
+    Command *cmdPtr,		/* Points to defintion of command being
+				 * compiled. */
+    CompileEnv *envPtr)		/* Holds resulting instructions. */
+{
+    DefineLineInformation;	/* TIP #280 */
+    Tcl_Token *tokenPtr = parsePtr->tokenPtr;
+    int i;
+
+    if (parsePtr->numWords < 2 || parsePtr->numWords > 255) {
+	return TCL_ERROR;
+    }
+
+    for (i=0 ; i<parsePtr->numWords ; i++) {
+	CompileWord(envPtr, tokenPtr, interp, i);
+	tokenPtr = TokenAfter(tokenPtr);
+    }
+    TclEmitInstInt1(	INST_TCLOO_NEXT_CLASS, i,	envPtr);
+    return TCL_OK;
+}
+
+int
 TclCompileObjectSelfCmd(
     Tcl_Interp *interp,		/* Used for error reporting. */
     Tcl_Parse *parsePtr,	/* Points to a parse structure for the command
diff --git a/generic/tclCompCmdsSZ.c b/generic/tclCompCmdsSZ.c
index c54a06a..4b14f24 100644
--- a/generic/tclCompCmdsSZ.c
+++ b/generic/tclCompCmdsSZ.c
@@ -3447,6 +3447,51 @@ TclCompileYieldCmd(
 /*
  *----------------------------------------------------------------------
  *
+ * TclCompileYieldToCmd --
+ *
+ *	Procedure called to compile the "yieldto" command.
+ *
+ * Results:
+ *	Returns TCL_OK for a successful compile. Returns TCL_ERROR to defer
+ *	evaluation to runtime.
+ *
+ * Side effects:
+ *	Instructions are added to envPtr to execute the "yieldto" command at
+ *	runtime.
+ *
+ *----------------------------------------------------------------------
+ */
+
+int
+TclCompileYieldToCmd(
+    Tcl_Interp *interp,		/* Used for error reporting. */
+    Tcl_Parse *parsePtr,	/* Points to a parse structure for the command
+				 * created by Tcl_ParseCommand. */
+    Command *cmdPtr,		/* Points to defintion of command being
+				 * compiled. */
+    CompileEnv *envPtr)		/* Holds resulting instructions. */
+{
+    DefineLineInformation;	/* TIP #280 */
+    Tcl_Token *tokenPtr = TokenAfter(parsePtr->tokenPtr);
+    int i;
+
+    if (parsePtr->numWords < 2) {
+	return TCL_ERROR;
+    }
+
+    OP(		NS_CURRENT);
+    for (i = 1 ; i < parsePtr->numWords ; i++) {
+	CompileWord(envPtr, tokenPtr, interp, i);
+	tokenPtr = TokenAfter(tokenPtr);
+    }
+    OP4(	LIST, i);
+    OP(		YIELD_TO_INVOKE);
+    return TCL_OK;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
  * CompileUnaryOpCmd --
  *
  *	Utility routine to compile the unary operator commands.
diff --git a/generic/tclCompile.c b/generic/tclCompile.c
index ee67e24..f75ac83 100644
--- a/generic/tclCompile.c
+++ b/generic/tclCompile.c
@@ -618,8 +618,25 @@ InstructionDesc const tclInstructionTable[] = {
 	 * Stack:  ... cmdName => ... fullOriginalCmdName */
 
     {"tclooNext",	 2,	INT_MIN,  1,	{OPERAND_UINT1}},
-	/* Push the identity of the current TclOO object (i.e., the name of
-	 * its current public access command) on the stack. */
+	/* Call the next item on the TclOO call chain, passing opnd arguments
+	 * (min 1, max 255, *includes* "next").  The result of the invoked
+	 * method implementation will be pushed on the stack in place of the
+	 * arguments (similar to invokeStk).
+	 * Stack:  ... "next" arg2 arg3 -- argN => ... result */
+    {"tclooNextClass",	 2,	INT_MIN,  1,	{OPERAND_UINT1}},
+	/* Call the following item on the TclOO call chain defined by class
+	 * className, passing opnd arguments (min 2, max 255, *includes*
+	 * "nextto" and the class name). The result of the invoked method
+	 * implementation will be pushed on the stack in place of the
+	 * arguments (similar to invokeStk).
+	 * Stack:  ... "nextto" className arg3 arg4 -- argN => ... result */
+
+    {"yieldToInvoke",	 1,	0,	  0,	{OPERAND_NONE}},
+	/* Makes the current coroutine yield the value at the top of the
+	 * stack, invoking the given command/args with resolution in the given
+	 * namespace (all packed into a list), and places the list of values
+	 * that are the response back on top of the stack when it resumes.
+	 * Stack:  ... [list ns cmd arg1 ... argN] => ... resumeList */
 
     {NULL, 0, 0, 0, {OPERAND_NONE}}
 };
diff --git a/generic/tclCompile.h b/generic/tclCompile.h
index 6ecadf4..7994e2c 100644
--- a/generic/tclCompile.h
+++ b/generic/tclCompile.h
@@ -791,9 +791,12 @@ typedef struct ByteCode {
 #define INST_ORIGIN_COMMAND		178
 
 #define INST_TCLOO_NEXT			179
+#define INST_TCLOO_NEXT_CLASS		180
+
+#define INST_YIELD_TO_INVOKE		181
 
 /* The last opcode */
-#define LAST_INST_OPCODE		179
+#define LAST_INST_OPCODE		181
 
 /*
  * Table describing the Tcl bytecode instructions: their name (for displaying
diff --git a/generic/tclExecute.c b/generic/tclExecute.c
index 5b42124..6749120 100644
--- a/generic/tclExecute.c
+++ b/generic/tclExecute.c
@@ -2494,9 +2494,12 @@ TEBCresume(
 	TRACE_APPEND(("\n"));
 	goto processExceptionReturn;
 
-    case INST_YIELD: {
-	CoroutineData *corPtr = iPtr->execEnvPtr->corPtr;
+    {
+	CoroutineData *corPtr;
+	int yieldParameter;
 
+    case INST_YIELD:
+	corPtr = iPtr->execEnvPtr->corPtr;
 	TRACE(("%.30s => ", O2S(OBJ_AT_TOS)));
 	if (!corPtr) {
 	    TRACE_APPEND(("ERROR: yield outside coroutine\n"));
@@ -2510,11 +2513,74 @@ TEBCresume(
 	}
 
 #ifdef TCL_COMPILE_DEBUG
-	TRACE_WITH_OBJ(("yield, result="), iPtr->objResultPtr);
-	if (traceInstructions) {
-	    fprintf(stdout, "\n");
+	if (tclTraceExec >= 2) {
+	    if (traceInstructions) {
+		TRACE_APPEND(("YIELD...\n"));
+	    } else {
+		fprintf(stdout, "%d: (%u) yielding value \"%.30s\"\n",
+			iPtr->numLevels, (unsigned)(pc - codePtr->codeStart),
+			Tcl_GetString(OBJ_AT_TOS));
+	    }
+	    fflush(stdout);
+	}
+#endif
+	yieldParameter = 0;
+	Tcl_SetObjResult(interp, OBJ_AT_TOS);
+	goto doYield;
+
+    case INST_YIELD_TO_INVOKE:
+	corPtr = iPtr->execEnvPtr->corPtr;
+	valuePtr = OBJ_AT_TOS;
+	if (!corPtr) {
+	    TRACE(("[%.30s] => ERROR: yield outside coroutine\n",
+		    O2S(valuePtr)));
+	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		    "yieldto can only be called in a coroutine", -1));
+	    DECACHE_STACK_INFO();
+	    Tcl_SetErrorCode(interp, "TCL", "COROUTINE", "ILLEGAL_YIELD",
+		    NULL);
+	    CACHE_STACK_INFO();
+	    goto gotError;
+	}
+	if (((Namespace *)TclGetCurrentNamespace(interp))->flags & NS_DYING) {
+	    TRACE(("[%.30s] => ERROR: yield in deleted\n",
+		    O2S(valuePtr)));
+	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		    "yieldto called in deleted namespace", -1));
+	    DECACHE_STACK_INFO();
+	    Tcl_SetErrorCode(interp, "TCL", "COROUTINE", "YIELDTO_IN_DELETED",
+		    NULL);
+	    CACHE_STACK_INFO();
+	    goto gotError;
+	}
+
+#ifdef TCL_COMPILE_DEBUG
+	if (tclTraceExec >= 2) {
+	    if (traceInstructions) {
+		TRACE(("[%.30s] => YIELD...\n", O2S(valuePtr)));
+	    } else {
+		/* FIXME: What is the right thing to trace? */
+		fprintf(stdout, "%d: (%u) yielding to [%.30s]\n",
+			iPtr->numLevels, (unsigned)(pc - codePtr->codeStart),
+			Tcl_GetString(valuePtr));
+	    }
+	    fflush(stdout);
 	}
 #endif
+
+	/*
+	 * Install a tailcall record in the caller and continue with the
+	 * yield. The yield is switched into multi-return mode (via the
+	 * 'yieldParameter').
+	 */
+
+	Tcl_IncrRefCount(valuePtr);
+	iPtr->execEnvPtr = corPtr->callerEEPtr;
+	TclSetTailcall(interp, valuePtr);
+	iPtr->execEnvPtr = corPtr->eePtr;
+	yieldParameter = (PTR2INT(NULL)+1);	/*==CORO_ACTIVATE_YIELDM*/
+
+    doYield:
 	/* TIP #280: Record the last piece of info needed by
 	 * 'TclGetSrcInfoForPc', and push the frame.
 	 */
@@ -2529,11 +2595,8 @@ TEBCresume(
 	pc++;
 	cleanup = 1;
 	TEBC_YIELD();
-	
-	Tcl_SetObjResult(interp, OBJ_AT_TOS);
 	TclNRAddCallback(interp, TclNRCoroutineActivateCallback, corPtr,
-		INT2PTR(0), NULL, NULL);
-
+		INT2PTR(yieldParameter), NULL, NULL);
 	return TCL_OK;
     }
 
@@ -2553,6 +2616,7 @@ TEBCresume(
 	}
 
 #ifdef TCL_COMPILE_DEBUG
+	/* FIXME: What is the right thing to trace? */
 	{
 	    register int i;
 
@@ -4539,6 +4603,7 @@ TEBCresume(
 	Object *oPtr;
 	CallFrame *framePtr;
 	CallContext *contextPtr;
+	int skip, newDepth;
 
     case INST_TCLOO_SELF:
 	framePtr = iPtr->varFramePtr;
@@ -4563,9 +4628,111 @@ TEBCresume(
 	TRACE_WITH_OBJ(("=> "), objResultPtr);
 	NEXT_INST_F(1, 0, 1);
 
+    case INST_TCLOO_NEXT_CLASS:
+	opnd = TclGetUInt1AtPtr(pc+1);
+	framePtr = iPtr->varFramePtr;
+	valuePtr = OBJ_AT_DEPTH(opnd - 2);
+	objv = &OBJ_AT_DEPTH(opnd - 1);
+	skip = 2;
+	TRACE(("%d => ", opnd));
+	if (framePtr == NULL ||
+		!(framePtr->isProcCallFrame & FRAME_IS_METHOD)) {
+	    TRACE_APPEND(("ERROR: no TclOO call context\n"));
+	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		    "nextto may only be called from inside a method",
+		    -1));
+	    DECACHE_STACK_INFO();
+	    Tcl_SetErrorCode(interp, "TCL", "OO", "CONTEXT_REQUIRED", NULL);
+	    CACHE_STACK_INFO();
+	    goto gotError;
+	}
+	contextPtr = framePtr->clientData;
+
+	oPtr = (Object *) Tcl_GetObjectFromObj(interp, valuePtr);
+	if (oPtr == NULL) {
+	    TRACE_APPEND(("ERROR: \"%.30s\" not object\n", O2S(valuePtr)));
+	    goto gotError;
+	} else {
+	    Class *classPtr = oPtr->classPtr;
+	    struct MInvoke *miPtr;
+	    int i;
+	    const char *methodType;
+
+	    if (classPtr == NULL) {
+		TRACE_APPEND(("ERROR: \"%.30s\" not class\n", O2S(valuePtr)));
+		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+			"\"%s\" is not a class", TclGetString(valuePtr)));
+		DECACHE_STACK_INFO();
+		Tcl_SetErrorCode(interp, "TCL", "OO", "CLASS_REQUIRED", NULL);
+		CACHE_STACK_INFO();
+		goto gotError;
+	    }
+
+	    for (i=contextPtr->index+1 ; i<contextPtr->callPtr->numChain ; i++) {
+		miPtr = contextPtr->callPtr->chain + i;
+		if (!miPtr->isFilter &&
+			miPtr->mPtr->declaringClassPtr == classPtr) {
+		    newDepth = i;
+#ifdef TCL_COMPILE_DEBUG
+		    if (tclTraceExec >= 2) {
+			if (traceInstructions) {
+			    strncpy(cmdNameBuf, TclGetString(objv[0]), 20);
+			} else {
+			    fprintf(stdout, "%d: (%u) invoking ",
+				    iPtr->numLevels,
+				    (unsigned)(pc - codePtr->codeStart));
+			}
+			for (i = 0;  i < opnd;  i++) {
+			    TclPrintObject(stdout, objv[i], 15);
+			    fprintf(stdout, " ");
+			}
+			fprintf(stdout, "\n");
+			fflush(stdout);
+		    }
+#endif /*TCL_COMPILE_DEBUG*/
+		    goto doInvokeNext;
+		}
+	    }
+
+	    if (contextPtr->callPtr->flags & CONSTRUCTOR) {
+		methodType = "constructor";
+	    } else if (contextPtr->callPtr->flags & DESTRUCTOR) {
+		methodType = "destructor";
+	    } else {
+		methodType = "method";
+	    }
+
+	    TRACE_APPEND(("ERROR: \"%.30s\" not on reachable chain\n",
+		    O2S(valuePtr)));
+	    for (i=contextPtr->index ; i>=0 ; i--) {
+		miPtr = contextPtr->callPtr->chain + i;
+		if (miPtr->isFilter
+			|| miPtr->mPtr->declaringClassPtr != classPtr) {
+		    continue;
+		}
+		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+			"%s implementation by \"%s\" not reachable from here",
+			methodType, TclGetString(valuePtr)));
+		DECACHE_STACK_INFO();
+		Tcl_SetErrorCode(interp, "TCL", "OO", "CLASS_NOT_REACHABLE",
+			NULL);
+		CACHE_STACK_INFO();
+		goto gotError;
+	    }
+	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+		    "%s has no non-filter implementation by \"%s\"",
+		    methodType, TclGetString(valuePtr)));
+	    DECACHE_STACK_INFO();
+	    Tcl_SetErrorCode(interp, "TCL", "OO", "CLASS_NOT_THERE", NULL);
+	    CACHE_STACK_INFO();
+	    goto gotError;
+	}
+
     case INST_TCLOO_NEXT:
 	opnd = TclGetUInt1AtPtr(pc+1);
+	objv = &OBJ_AT_DEPTH(opnd - 1);
 	framePtr = iPtr->varFramePtr;
+	skip = 1;
 	TRACE(("%d => ", opnd));
 	if (framePtr == NULL ||
 		!(framePtr->isProcCallFrame & FRAME_IS_METHOD)) {
@@ -4580,7 +4747,8 @@ TEBCresume(
 	}
 	contextPtr = framePtr->clientData;
 
-	if (contextPtr->index+1 >= contextPtr->callPtr->numChain) {
+	newDepth = contextPtr->index + 1;
+	if (newDepth >= contextPtr->callPtr->numChain) {
 	    /*
 	     * We're at the end of the chain; generate an error message unless
 	     * the interpreter is being torn down, in which case we might be
@@ -4605,33 +4773,31 @@ TEBCresume(
 	    Tcl_SetErrorCode(interp, "TCL", "OO", "NOTHING_NEXT", NULL);
 	    CACHE_STACK_INFO();
 	    goto gotError;
-	}
-
 #ifdef TCL_COMPILE_DEBUG
-	if (tclTraceExec >= 2) {
+	} else if (tclTraceExec >= 2) {
 	    int i;
 
 	    if (traceInstructions) {
 		strncpy(cmdNameBuf, TclGetString(objv[0]), 20);
-		TRACE(("next_in_chain "));
 	    } else {
-		fprintf(stdout, "%d: (%u) invoking next_in_chain ",
+		fprintf(stdout, "%d: (%u) invoking ",
 			iPtr->numLevels, (unsigned)(pc - codePtr->codeStart));
 	    }
-	    for (i = 0;  i < objc;  i++) {
+	    for (i = 0;  i < opnd;  i++) {
 		TclPrintObject(stdout, objv[i], 15);
 		fprintf(stdout, " ");
 	    }
 	    fprintf(stdout, "\n");
 	    fflush(stdout);
-	}
 #endif /*TCL_COMPILE_DEBUG*/
+	}
 
+    doInvokeNext:
 	bcFramePtr->data.tebc.pc = (char *) pc;
 	iPtr->cmdFramePtr = bcFramePtr;
 
 	if (iPtr->flags & INTERP_DEBUG_FRAME) {
-	    ArgumentBCEnter(interp, codePtr, TD, pc, objc, objv);
+	    ArgumentBCEnter(interp, codePtr, TD, pc, opnd, objv);
 	}
 
 	pcAdjustment = 2;
@@ -4640,6 +4806,7 @@ TEBCresume(
 	iPtr->varFramePtr = framePtr->callerVarPtr;
 	pc += pcAdjustment;
 	TEBC_YIELD();
+
 	oPtr = contextPtr->oPtr;
 	if (oPtr->flags & FILTER_HANDLING) {
 	    TclNRAddCallback(interp, FinalizeOONextFilter,
@@ -4650,20 +4817,21 @@ TEBCresume(
 		    framePtr, contextPtr, INT2PTR(contextPtr->index),
 		    INT2PTR(contextPtr->skip));
 	}
-	if (contextPtr->callPtr->chain[++contextPtr->index].isFilter
+	contextPtr->skip = skip;
+	contextPtr->index = newDepth;
+	if (contextPtr->callPtr->chain[newDepth].isFilter
 		|| contextPtr->callPtr->flags & FILTER_HANDLING) {
 	    oPtr->flags |= FILTER_HANDLING;
 	} else {
 	    oPtr->flags &= ~FILTER_HANDLING;
 	}
-	contextPtr->skip = 1;
+
 	{
 	    register Method *const mPtr =
-		    contextPtr->callPtr->chain[contextPtr->index].mPtr;
+		    contextPtr->callPtr->chain[newDepth].mPtr;
 
 	    return mPtr->typePtr->callProc(mPtr->clientData, interp,
-		    (Tcl_ObjectContext) contextPtr, opnd,
-		    &OBJ_AT_DEPTH(opnd-1));
+		    (Tcl_ObjectContext) contextPtr, opnd, objv);
 	}
 
     case INST_TCLOO_IS_OBJECT:
diff --git a/generic/tclInt.h b/generic/tclInt.h
index 3aaa30b..6ddb015 100644
--- a/generic/tclInt.h
+++ b/generic/tclInt.h
@@ -3592,6 +3592,9 @@ MODULE_SCOPE int	TclCompileNoOp(Tcl_Interp *interp,
 MODULE_SCOPE int	TclCompileObjectNextCmd(Tcl_Interp *interp,
 			    Tcl_Parse *parsePtr, Command *cmdPtr,
 			    struct CompileEnv *envPtr);
+MODULE_SCOPE int	TclCompileObjectNextToCmd(Tcl_Interp *interp,
+			    Tcl_Parse *parsePtr, Command *cmdPtr,
+			    struct CompileEnv *envPtr);
 MODULE_SCOPE int	TclCompileObjectSelfCmd(Tcl_Interp *interp,
 			    Tcl_Parse *parsePtr, Command *cmdPtr,
 			    struct CompileEnv *envPtr);
@@ -3685,6 +3688,9 @@ MODULE_SCOPE int	TclCompileWhileCmd(Tcl_Interp *interp,
 MODULE_SCOPE int	TclCompileYieldCmd(Tcl_Interp *interp,
 			    Tcl_Parse *parsePtr, Command *cmdPtr,
 			    struct CompileEnv *envPtr);
+MODULE_SCOPE int	TclCompileYieldToCmd(Tcl_Interp *interp,
+			    Tcl_Parse *parsePtr, Command *cmdPtr,
+			    struct CompileEnv *envPtr);
 MODULE_SCOPE int	TclCompileBasic0ArgCmd(Tcl_Interp *interp,
 			    Tcl_Parse *parsePtr, Command *cmdPtr,
 			    struct CompileEnv *envPtr);
diff --git a/generic/tclOO.c b/generic/tclOO.c
index 9a0682d..de00733 100644
--- a/generic/tclOO.c
+++ b/generic/tclOO.c
@@ -440,8 +440,9 @@ InitFoundation(
     cmdPtr = (Command *) Tcl_NRCreateCommand(interp, "::oo::Helpers::next",
 	    NULL, TclOONextObjCmd, NULL, NULL);
     cmdPtr->compileProc = TclCompileObjectNextCmd;
-    Tcl_NRCreateCommand(interp, "::oo::Helpers::nextto",
+    cmdPtr = (Command *) Tcl_NRCreateCommand(interp, "::oo::Helpers::nextto",
 	    NULL, TclOONextToObjCmd, NULL, NULL);
+    cmdPtr->compileProc = TclCompileObjectNextToCmd;
     cmdPtr = (Command *) Tcl_CreateObjCommand(interp, "::oo::Helpers::self",
 	    TclOOSelfObjCmd, NULL, NULL);
     cmdPtr->compileProc = TclCompileObjectSelfCmd;
diff --git a/generic/tclOOBasic.c b/generic/tclOOBasic.c
index 6084cf2..0b0516b 100644
--- a/generic/tclOOBasic.c
+++ b/generic/tclOOBasic.c
@@ -821,6 +821,7 @@ TclOONextToObjCmd(
     CallContext *contextPtr;
     int i;
     Tcl_Object object;
+    const char *methodType;
 
     /*
      * Start with sanity checks on the calling context to make sure that we
@@ -886,19 +887,30 @@ TclOONextToObjCmd(
      * is on the chain but unreachable, or not on the chain at all.
      */
 
+    if (contextPtr->callPtr->flags & CONSTRUCTOR) {
+	methodType = "constructor";
+    } else if (contextPtr->callPtr->flags & DESTRUCTOR) {
+	methodType = "destructor";
+    } else {
+	methodType = "method";
+    }
+
     for (i=contextPtr->index ; i>=0 ; i--) {
 	struct MInvoke *miPtr = contextPtr->callPtr->chain + i;
 
 	if (!miPtr->isFilter && miPtr->mPtr->declaringClassPtr == classPtr) {
 	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
-		    "method implementation by \"%s\" not reachable from here",
-		    TclGetString(objv[1])));
+		    "%s implementation by \"%s\" not reachable from here",
+		    methodType, TclGetString(objv[1])));
+	    Tcl_SetErrorCode(interp, "TCL", "OO", "CLASS_NOT_REACHABLE",
+		    NULL);
 	    return TCL_ERROR;
 	}
     }
     Tcl_SetObjResult(interp, Tcl_ObjPrintf(
-	    "method has no non-filter implementation by \"%s\"",
-	    TclGetString(objv[1])));
+	    "%s has no non-filter implementation by \"%s\"",
+	    methodType, TclGetString(objv[1])));
+    Tcl_SetErrorCode(interp, "TCL", "OO", "CLASS_NOT_THERE", NULL);
     return TCL_ERROR;
 }