Changes so that user-defined classes can implement operations invoked

by special syntax: you can now define your own numbers, sequences and
mappings.

5 files changed, 609 insertions, 42 deletions

diff --git a/Include/ceval.h b/Include/ceval.h
index d9708a2..dc31255 100644
--- a/Include/ceval.h
+++ b/Include/ceval.h
@@ -77,13 +77,13 @@ void flushline PROTO((void));
 */
 
 extern void init_save_thread PROTO((void));
-extern void *save_thread PROTO((void));
-extern void restore_thread PROTO((void *));
+extern object *save_thread PROTO((void));
+extern void restore_thread PROTO((object *));
 
 #ifdef USE_THREAD
 
 #define BGN_SAVE { \
-			void *_save; \
+			object *_save; \
 			_save = save_thread();
 #define RET_SAVE	restore_thread(_save);
 #define RES_SAVE	_save = save_thread();
diff --git a/Include/classobject.h b/Include/classobject.h
index 7dd66e7..1d24a7c 100644
--- a/Include/classobject.h
+++ b/Include/classobject.h
@@ -42,3 +42,6 @@ extern object *newinstancemethodobject PROTO((object *, object *));
 
 extern object *instancemethodgetfunc PROTO((object *));
 extern object *instancemethodgetself PROTO((object *));
+
+extern int instance_coerce PROTO((object **, object **));
+extern object *instance_convert PROTO((object *, char *));
diff --git a/Objects/classobject.c b/Objects/classobject.c
index ed0e6f4..40fe0c9 100644
--- a/Objects/classobject.c
+++ b/Objects/classobject.c
@@ -25,8 +25,12 @@ OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 /* Class object implementation */
 
 #include "allobjects.h"
-
+#include "modsupport.h"
 #include "structmember.h"
+#include "ceval.h"
+
+extern typeobject MappingInstancetype;
+extern typeobject SequenceInstancetype;
 
 typedef struct {
 	OB_HEAD
@@ -166,6 +170,7 @@ newinstanceobject(class)
 	register object *class;
 {
 	register instanceobject *inst;
+	object *v;
 	if (!is_classobject(class)) {
 		err_badcall();
 		return NULL;
@@ -246,6 +251,428 @@ instance_setattr(inst, name, v)
 		return dictinsert(inst->in_attr, name, v);
 }
 
+int
+instance_print(inst, fp, flags)
+	instanceobject *inst;
+	FILE *fp;
+	int flags;
+{
+	object *func, *repr;
+	int ret;
+
+	func = instance_getattr(inst, "__repr__");
+	if (func == NULL) {
+		err_clear();
+		fprintf(fp, "<instance object at %lx>", (long)inst);
+		return 0;
+	}
+	repr = call_object(func, (object *)NULL);
+	DECREF(func);
+	if (repr == NULL)
+		return -1;
+	ret = printobject(repr, fp, flags | PRINT_RAW);
+	DECREF(repr);
+	return ret;
+}
+
+object *
+instance_repr(inst)
+	instanceobject *inst;
+{
+	object *func;
+	object *res;
+
+	func = instance_getattr(inst, "__repr__");
+	if (func == NULL) {
+		char buf[80];
+		err_clear();
+		sprintf(buf, "<instance object at %lx>", (long)inst);
+		return newstringobject(buf);
+	}
+	res = call_object(func, (object *)NULL);
+	DECREF(func);
+	return res;
+}
+
+int
+instance_compare(inst, other)
+	instanceobject *inst, *other;
+{
+	object *func;
+	object *res;
+	int outcome;
+
+	func = instance_getattr(inst, "__cmp__");
+	if (func == NULL) {
+		err_clear();
+		if (inst < other)
+			return -1;
+		if (inst > other)
+			return 1;
+		return 0;
+	}
+	res = call_object(func, (object *)other);
+	DECREF(func);
+	if (res == NULL) {
+		err_clear(); /* XXX Should report the error, bot how...??? */
+		return 0;
+	}
+	if (is_intobject(res))
+		outcome = getintvalue(res);
+	else
+		outcome = 0; /* XXX Should report the error, bot how...??? */
+	DECREF(res);
+	return outcome;
+}
+
+int
+instance_length(inst)
+	instanceobject *inst;
+{
+	object *func;
+	object *res;
+	int outcome;
+
+	func = instance_getattr(inst, "__len__");
+	if (func == NULL)
+		return -1;
+	res = call_object(func, (object *)NULL);
+	DECREF(func);
+	if (is_intobject(res)) {
+		outcome = getintvalue(res);
+		if (outcome < 0)
+			err_setstr(ValueError, "__len__() should return >= 0");
+	}
+	else {
+		err_setstr(TypeError, "__len__() should return an int");
+		outcome = -1;
+	}
+	DECREF(res);
+	return outcome;
+}
+
+object *
+instance_subscript(inst, key)
+	instanceobject *inst;
+	object *key;
+{
+	object *func;
+	object *arg;
+	object *res;
+
+	func = instance_getattr(inst, "__getitem__");
+	if (func == NULL)
+		return NULL;
+	arg = mkvalue("(O)", key);
+	if (arg == NULL) {
+		DECREF(func);
+		return NULL;
+	}
+	res = call_object(func, arg);
+	DECREF(func);
+	DECREF(arg);
+	return res;
+}
+
+int
+instance_ass_subscript(inst, key, value)
+	instanceobject*inst;
+	object *key;
+	object *value;
+{
+	object *func;
+	object *arg;
+	object *res;
+
+	if (value == NULL)
+		func = instance_getattr(inst, "__delitem__");
+	else
+		func = instance_getattr(inst, "__setitem__");
+	if (func == NULL)
+		return -1;
+	if (value == NULL)
+		arg = mkvalue("(O)", key);
+	else
+		arg = mkvalue("(OO)", key, value);
+	if (arg == NULL) {
+		DECREF(func);
+		return NULL;
+	}
+	res = call_object(func, arg);
+	DECREF(func);
+	DECREF(arg);
+	if (res == NULL)
+		return -1;
+	DECREF(res);
+	return 0;
+}
+
+mapping_methods instance_as_mapping = {
+	instance_length,	/*mp_length*/
+	instance_subscript,	/*mp_subscript*/
+	instance_ass_subscript,	/*mp_ass_subscript*/
+};
+
+static object *
+instance_concat(inst, other)
+	instanceobject *inst, *other;
+{
+	object *func, *res;
+
+	func = instance_getattr(inst, "__add__");
+	if (func == NULL)
+		return NULL;
+	res = call_object(func, (object *)other);
+	DECREF(func);
+	return res;
+}
+
+static object *
+instance_repeat(inst, count)
+	instanceobject *inst;
+	int count;
+{
+	object *func, *arg, *res;
+
+	func = instance_getattr(inst, "__mul__");
+	if (func == NULL)
+		return NULL;
+	arg = newintobject((long)count);
+	if (arg == NULL) {
+		DECREF(func);
+		return NULL;
+	}
+	res = call_object(func, arg);
+	DECREF(func);
+	DECREF(arg);
+	return res;
+}
+
+static object *
+instance_item(inst, i)
+	instanceobject *inst;
+	int i;
+{
+	object *func, *arg, *res;
+
+	func = instance_getattr(inst, "__getitem__");
+	if (func == NULL)
+		return NULL;
+	arg = newintobject((long)i);
+	if (arg == NULL) {
+		DECREF(func);
+		return NULL;
+	}
+	res = call_object(func, arg);
+	DECREF(func);
+	DECREF(arg);
+	return res;
+}
+
+static object *
+instance_slice(inst, i, j)
+	instanceobject *inst;
+	int i, j;
+{
+	object *func, *arg, *res;
+
+	func = instance_getattr(inst, "__getslice__");
+	if (func == NULL)
+		return NULL;
+	arg = mkvalue("(ii)", i, j);
+	if (arg == NULL) {
+		DECREF(func);
+		return NULL;
+	}
+	res = call_object(func, arg);
+	DECREF(func);
+	DECREF(arg);
+	return res;
+}
+
+static int
+instance_ass_item(inst, i, item)
+	instanceobject *inst;
+	int i;
+	object *item;
+{
+	object *func, *arg, *res;
+
+	if (item == NULL)
+		func = instance_getattr(inst, "__delitem__");
+	else
+		func = instance_getattr(inst, "__setitem__");
+	if (func == NULL)
+		return NULL;
+	if (item == NULL)
+		arg = mkvalue("i", i);
+	else
+		arg = mkvalue("(iO)", i, item);
+	if (arg == NULL) {
+		DECREF(func);
+		return NULL;
+	}
+	res = call_object(func, arg);
+	DECREF(func);
+	DECREF(arg);
+	if (res == NULL)
+		return -1;
+	DECREF(res);
+	return 0;
+}
+
+static int
+instance_ass_slice(inst, i, j, value)
+	instanceobject *inst;
+	int i, j;
+	object *value;
+{
+	object *func, *arg, *res;
+
+	if (value == NULL)
+		func = instance_getattr(inst, "__delslice__");
+	else
+		func = instance_getattr(inst, "__setslice__");
+	if (func == NULL)
+		return NULL;
+	if (value == NULL)
+		arg = mkvalue("(ii)", i, j);
+	else
+		arg = mkvalue("(iiO)", i, j, value);
+	if (arg == NULL) {
+		DECREF(func);
+		return NULL;
+	}
+	res = call_object(func, arg);
+	DECREF(func);
+	DECREF(arg);
+	if (res == NULL)
+		return -1;
+	DECREF(res);
+	return 0;
+}
+
+static sequence_methods instance_as_sequence = {
+	instance_length,	/*sq_length*/
+	instance_concat,	/*sq_concat*/
+	instance_repeat,	/*sq_repeat*/
+	instance_item,		/*sq_item*/
+	instance_slice,		/*sq_slice*/
+	instance_ass_item,	/*sq_ass_item*/
+	instance_ass_slice,	/*sq_ass_slice*/
+};
+
+static object *
+generic_binary_op(self, other, methodname)
+	instanceobject *self;
+	object *other;
+	char *methodname;
+{
+	object *func, *res;
+
+	if ((func = instance_getattr(self, methodname)) == NULL)
+		return NULL;
+	res = call_object(func, other);
+	DECREF(func);
+	return res;
+}
+
+static object *
+generic_unary_op(self, methodname)
+	instanceobject *self;
+	char *methodname;
+{
+	object *func, *res;
+
+	if ((func = instance_getattr(self, methodname)) == NULL)
+		return NULL;
+	res = call_object(func, (object *)NULL);
+	DECREF(func);
+	return res;
+}
+
+#define BINARY(funcname, methodname) \
+static object * funcname(self, other) instanceobject *self; object *other; { \
+	return generic_binary_op(self, other, methodname); \
+}
+
+#define UNARY(funcname, methodname) \
+static object *funcname(self) instanceobject *self; { \
+	return generic_unary_op(self, methodname); \
+}
+
+BINARY(instance_add, "__add__")
+BINARY(instance_sub, "__sub__")
+BINARY(instance_mul, "__mul__")
+BINARY(instance_div, "__div__")
+BINARY(instance_mod, "__mod__")
+BINARY(instance_divmod, "__divmod__")
+BINARY(instance_pow, "__pow__")
+UNARY(instance_neg, "__neg__")
+UNARY(instance_pos, "__pos__")
+UNARY(instance_abs, "__abs__")
+
+int
+instance_nonzero(self)
+	instanceobject *self;
+{
+	object *func, *res;
+	long outcome;
+
+	if ((func = instance_getattr(self, "__len__")) == NULL) {
+		err_clear();
+		if ((func = instance_getattr(self, "__nonzero__")) == NULL) {
+			err_clear();
+			/* Fall back to the default behavior:
+			   all instances are nonzero */
+			return 1;
+		}
+	}
+	res = call_object(func, (object *)NULL);
+	DECREF(func);
+	if (res == NULL)
+		return -1;
+	if (!is_intobject(res)) {
+		DECREF(res);
+		err_setstr(TypeError, "__nonzero__ should return an int");
+		return -1;
+	}
+	outcome = getintvalue(res);
+	DECREF(res);
+	if (outcome < 0) {
+		err_setstr(ValueError, "__nonzero__ should return >= 0");
+		return -1;
+	}
+	return outcome > 0;
+}
+
+UNARY(instance_invert, "__invert__")
+BINARY(instance_lshift, "__lshift__")
+BINARY(instance_rshift, "__rshift__")
+BINARY(instance_and, "__and__")
+BINARY(instance_xor, "__xor__")
+BINARY(instance_or, "__or__")
+
+static number_methods instance_as_number = {
+	instance_add,		/*nb_add*/
+	instance_sub,		/*nb_subtract*/
+	instance_mul,		/*nb_multiply*/
+	instance_div,		/*nb_divide*/
+	instance_mod,		/*nb_remainder*/
+	instance_divmod,	/*nb_divmod*/
+	instance_pow,		/*nb_power*/
+	instance_neg,		/*nb_negative*/
+	instance_pos,		/*nb_positive*/
+	instance_abs,		/*nb_absolute*/
+	instance_nonzero,	/*nb_nonzero*/
+	instance_invert,	/*nb_invert*/
+	instance_lshift,	/*nb_lshift*/
+	instance_rshift,	/*nb_rshift*/
+	instance_and,		/*nb_and*/
+	instance_xor,		/*nb_xor*/
+	instance_or,		/*nb_or*/
+};
+
 typeobject Instancetype = {
 	OB_HEAD_INIT(&Typetype)
 	0,
@@ -253,16 +680,76 @@ typeobject Instancetype = {
 	sizeof(instanceobject),
 	0,
 	instance_dealloc,	/*tp_dealloc*/
-	0,			/*tp_print*/
+	instance_print,		/*tp_print*/
 	instance_getattr,	/*tp_getattr*/
 	instance_setattr,	/*tp_setattr*/
-	0,			/*tp_compare*/
-	0,			/*tp_repr*/
-	0,			/*tp_as_number*/
-	0,			/*tp_as_sequence*/
-	0,			/*tp_as_mapping*/
+	instance_compare,	/*tp_compare*/
+	instance_repr,		/*tp_repr*/
+	&instance_as_number,	/*tp_as_number*/
+	&instance_as_sequence,	/*tp_as_sequence*/
+	&instance_as_mapping,	/*tp_as_mapping*/
 };
 
+static int
+one_coerce(pv, pw)
+	object **pv, **pw;
+{
+	object *v = *pv;
+	object *w = *pw;
+	object *func;
+
+	if (!is_instanceobject(v))
+		return 1;
+	func = instance_getattr((instanceobject *)v, "__coerce__");
+	if (func == NULL) {
+		err_clear();
+		return 1;
+	}
+	if (func != NULL) {
+		object *res = call_object(func, w);
+		int outcome;
+		if (res == NULL)
+			return -1;
+		outcome = getargs(res, "(OO)", &v, &w);
+		if (!outcome || v->ob_type != w->ob_type ||
+			        v->ob_type->tp_as_number == NULL) {
+			DECREF(res);
+			err_setstr(TypeError, "bad __coerce__ result");
+			return -1;
+		}
+		INCREF(v);
+		INCREF(w);
+		DECREF(res);
+		*pv = v;
+		*pw = w;
+		return 0;
+	}
+}
+
+int
+instance_coerce(pv, pw)
+	object **pv, **pw;
+{
+	int outcome;
+	outcome = one_coerce(pv, pw);
+	if (outcome > 0) {
+		outcome = one_coerce(pw, pv);
+		if (outcome > 0) {
+			err_setstr(TypeError, "uncoerceable instance");
+			outcome = -1;
+		}
+	}
+	return outcome;
+}
+
+object *
+instance_convert(inst, methodname)
+	object *inst;
+	char *methodname;
+{
+	return generic_unary_op((instanceobject *)inst, methodname);
+}
+
 
 /* And finally, here are instance method objects */
 
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index ca5043d..cce19e1 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -85,6 +85,24 @@ builtin_chr(self, v)
 }
 
 static object *
+builtin_coerce(self, args)
+	object *self;
+	object *args;
+{
+	object *v, *w;
+	object *res;
+
+	if (!getargs(args, "(OO)", &v, &w))
+		return NULL;
+	if (coerce(&v, &w) < 0)
+		return NULL;
+	res = mkvalue("(OO)", v, w);
+	DECREF(v);
+	DECREF(w);
+	return res;
+}
+
+static object *
 builtin_dir(self, v)
 	object *self;
 	object *v;
@@ -250,6 +268,9 @@ builtin_float(self, v)
 		INCREF(v);
 		return v;
 	}
+	else if (is_instanceobject(v)) {
+		return instance_convert(v, "__float__");
+	}
 	err_setstr(TypeError, "float() argument must be int, long or float");
 	return NULL;
 }
@@ -359,6 +380,9 @@ builtin_int(self, v)
 		/* XXX should check for overflow */
 		return newintobject((long)x);
 	}
+	else if (is_instanceobject(v)) {
+		return instance_convert(v, "__int__");
+	}
 	err_setstr(TypeError, "int() argument must be int, long or float");
 	return NULL;
 }
@@ -385,7 +409,10 @@ builtin_len(self, v)
 		err_setstr(TypeError, "len() of unsized object");
 		return NULL;
 	}
-	return newintobject(len);
+	if (len < 0)
+		return NULL;
+	else
+		return newintobject(len);
 }
 
 static object *
@@ -407,6 +434,9 @@ builtin_long(self, v)
 		double x = getfloatvalue(v);
 		return dnewlongobject(x);
 	}
+	else if (is_instanceobject(v)) {
+		return instance_convert(v, "__long__");
+	}
 	err_setstr(TypeError, "long() argument must be int, long or float");
 	return NULL;
 }
@@ -648,6 +678,7 @@ static struct methodlist builtin_methods[] = {
 	{"abs",		builtin_abs},
 	{"apply",	builtin_apply},
 	{"chr",		builtin_chr},
+	{"coerce",	builtin_coerce},
 	{"dir",		builtin_dir},
 	{"divmod",	builtin_divmod},
 	{"eval",	builtin_eval},
@@ -766,6 +797,8 @@ coerce(pv, pw)
 		INCREF(w);
 		return 0;
 	}
+	if (is_instanceobject(v) || is_instanceobject(w))
+		return instance_coerce(pv, pw);
 	if (v->ob_type->tp_as_number == NULL ||
 					w->ob_type->tp_as_number == NULL) {
 		err_setstr(TypeError, "mixing number and non-number");
diff --git a/Python/ceval.c b/Python/ceval.c
index 252b1dc..ad679a6 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -36,6 +36,9 @@ OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 #include "bltinmodule.h"
 #include "traceback.h"
 
+/* Turn this on if your compiler chokes on the big switch: */
+/* #define CASE_TOO_BIG 1 /**/
+
 #ifndef NDEBUG
 /* For debugging the interpreter: */
 #define LLTRACE  1	/* Low-level trace feature */
@@ -106,13 +109,13 @@ init_save_thread()
    dynamically loaded modules needn't be compiled separately for use
    with and without threads: */
 
-void *
+object *
 save_thread()
 {
 #ifdef USE_THREAD
 	if (interpreter_lock) {
-		void *res;
-		res = (void *)current_frame;
+		object *res;
+		res = (object *)current_frame;
 		current_frame = NULL;
 		release_lock(interpreter_lock);
 		return res;
@@ -124,7 +127,7 @@ save_thread()
 
 void
 restore_thread(x)
-	void *x;
+	object *x;
 {
 #ifdef USE_THREAD
 	if (interpreter_lock) {
@@ -722,6 +725,10 @@ eval_code(co, globals, locals, arg)
 			if ((err = dict2remove(f->f_locals, w)) != 0)
 				err_setstr(NameError, getstringvalue(w));
 			break;
+
+#ifdef CASE_TOO_BIG
+		default: switch (opcode) {
+#endif
 		
 		case UNPACK_VARARG:
 			if (EMPTY()) {
@@ -1023,13 +1030,19 @@ eval_code(co, globals, locals, arg)
 			break;
 		
 		case JUMP_IF_FALSE:
-			if (!testbool(TOP()))
+			err = testbool(TOP());
+			if (err > 0)
+				err = 0;
+			else if (err == 0)
 				JUMPBY(oparg);
 			break;
 		
 		case JUMP_IF_TRUE:
-			if (testbool(TOP()))
+			err = testbool(TOP());
+			if (err > 0) {
+				err = 0;
 				JUMPBY(oparg);
+			}
 			break;
 		
 		case JUMP_ABSOLUTE:
@@ -1092,7 +1105,11 @@ eval_code(co, globals, locals, arg)
 			err_setstr(SystemError, "eval_code: unknown opcode");
 			why = WHY_EXCEPTION;
 			break;
-		
+
+#ifdef CASE_TOO_BIG
+		}
+#endif
+
 		} /* switch */
 
 	    on_error:
@@ -1388,22 +1405,27 @@ flushline()
 }
 
 
-/* Test a value used as condition, e.g., in a for or if statement */
+/* Test a value used as condition, e.g., in a for or if statement.
+   Return -1 if an error occurred */
 
 static int
 testbool(v)
 	object *v;
 {
+	int res;
 	if (v == None)
-		return 0;
-	if (v->ob_type->tp_as_number != NULL)
-		return (*v->ob_type->tp_as_number->nb_nonzero)(v);
-	if (v->ob_type->tp_as_sequence != NULL)
-		return (*v->ob_type->tp_as_sequence->sq_length)(v) != 0;
-	if (v->ob_type->tp_as_mapping != NULL)
-		return (*v->ob_type->tp_as_mapping->mp_length)(v) != 0;
-	/* All other objects are 'true' */
-	return 1;
+		res = 0;
+	else if (v->ob_type->tp_as_number != NULL)
+		res = (*v->ob_type->tp_as_number->nb_nonzero)(v);
+	else if (v->ob_type->tp_as_mapping != NULL)
+		res = (*v->ob_type->tp_as_mapping->mp_length)(v);
+	else if (v->ob_type->tp_as_sequence != NULL)
+		res = (*v->ob_type->tp_as_sequence->sq_length)(v);
+	else
+		res = 0;
+	if (res > 0)
+		res = 1;
+	return res;
 }
 
 static object *
@@ -1649,7 +1671,13 @@ not(v)
 	object *v;
 {
 	int outcome = testbool(v);
-	object *w = outcome == 0 ? True : False;
+	object *w;
+	if (outcome < 0)
+		return NULL;
+	if (outcome == 0)
+		w = True;
+	else
+		w = False;
 	INCREF(w);
 	return w;
 }
@@ -1780,18 +1808,24 @@ apply_subscript(v, w)
 		err_setstr(TypeError, "unsubscriptable object");
 		return NULL;
 	}
-	if (tp->tp_as_sequence != NULL) {
+	if (tp->tp_as_mapping != NULL) {
+		return (*tp->tp_as_mapping->mp_subscript)(v, w);
+	}
+	else {
 		int i;
 		if (!is_intobject(w)) {
 			err_setstr(TypeError, "sequence subscript not int");
 			return NULL;
 		}
 		i = getintvalue(w);
-		if (i < 0)
-			i += (*tp->tp_as_sequence->sq_length)(v);
+		if (i < 0) {
+			int len = (*tp->tp_as_sequence->sq_length)(v);
+			if (len < 0)
+				return NULL;
+			i += len;
+		}
 		return (*tp->tp_as_sequence->sq_item)(v, i);
 	}
-	return (*tp->tp_as_mapping->mp_subscript)(v, w);
 }
 
 static object *
@@ -1841,6 +1875,8 @@ apply_slice(u, v, w) /* return u[v:w] */
 	}
 	ilow = 0;
 	isize = ihigh = (*tp->tp_as_sequence->sq_length)(u);
+	if (isize < 0)
+		return NULL;
 	if (slice_index(v, isize, &ilow) != 0)
 		return NULL;
 	if (slice_index(w, isize, &ihigh) != 0)
@@ -1858,7 +1894,11 @@ assign_subscript(w, key, v) /* w[key] = v */
 	sequence_methods *sq;
 	mapping_methods *mp;
 	int (*func)();
-	if ((sq = tp->tp_as_sequence) != NULL &&
+	if ((mp = tp->tp_as_mapping) != NULL &&
+			(func = mp->mp_ass_subscript) != NULL) {
+		return (*func)(w, key, v);
+	}
+	else if ((sq = tp->tp_as_sequence) != NULL &&
 			(func = sq->sq_ass_item) != NULL) {
 		if (!is_intobject(key)) {
 			err_setstr(TypeError,
@@ -1867,15 +1907,15 @@ assign_subscript(w, key, v) /* w[key] = v */
 		}
 		else {
 			int i = getintvalue(key);
-			if (i < 0)
-				i += (*sq->sq_length)(w);
+			if (i < 0) {
+				int len = (*sq->sq_length)(w);
+				if (len < 0)
+					return -1;
+				i += len;
+			}
 			return (*func)(w, i, v);
 		}
 	}
-	else if ((mp = tp->tp_as_mapping) != NULL &&
-			(func = mp->mp_ass_subscript) != NULL) {
-		return (*func)(w, key, v);
-	}
 	else {
 		err_setstr(TypeError,
 				"can't assign to this subscripted object");
@@ -1899,6 +1939,8 @@ assign_slice(u, v, w, x) /* u[v:w] = x */
 	}
 	ilow = 0;
 	isize = ihigh = (*sq->sq_length)(u);
+	if (isize < 0)
+		return -1;
 	if (slice_index(v, isize, &ilow) != 0)
 		return -1;
 	if (slice_index(w, isize, &ihigh) != 0)
@@ -1955,6 +1997,8 @@ cmp_member(v, w)
 		return -1;
 	}
 	n = (*sq->sq_length)(w);
+	if (n < 0)
+		return -1;
 	for (i = 0; i < n; i++) {
 		x = (*sq->sq_item)(w, i);
 		cmp = cmpobject(v, x);
@@ -1977,7 +2021,7 @@ cmp_outcome(op, v, w)
 	case IS:
 	case IS_NOT:
 		res = (v == w);
-		if (op == IS_NOT)
+		if (op == (int) IS_NOT)
 			res = !res;
 		break;
 	case IN:
@@ -1985,7 +2029,7 @@ cmp_outcome(op, v, w)
 		res = cmp_member(v, w);
 		if (res < 0)
 			return NULL;
-		if (op == NOT_IN)
+		if (op == (int) NOT_IN)
 			res = !res;
 		break;
 	case EXC_MATCH: