[GR-23236] Fix test_genexps.

PullRequest: graalpython/1189

Author: steve-s

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/parser/sst/FactorySSTVisitor.java

@@ -57,6 +57,7 @@
 import java.util.Map;
 
 import com.oracle.graal.python.PythonLanguage;
+import com.oracle.graal.python.builtins.PythonBuiltinClassType;
 import com.oracle.graal.python.builtins.objects.PEllipsis;
 import com.oracle.graal.python.builtins.objects.PNone;
 import com.oracle.graal.python.builtins.objects.complex.PComplex;
@@ -347,8 +348,12 @@ public PNode visit(AugAssignmentSSTNode node) {
 
     private void checkCannotAssignTo(SSTNode lhs) throws RuntimeException {
         if (lhs instanceof ForComprehensionSSTNode) {
+            PythonBuiltinClassType resultType = ((ForComprehensionSSTNode) lhs).resultType;
+            if (resultType == PythonBuiltinClassType.PGenerator) {
+                throw errors.raiseInvalidSyntax(source, createSourceSection(lhs.startOffset, lhs.endOffset), "cannot assign to generator expression");
+            }
             String calleeName;
-            switch (((ForComprehensionSSTNode) lhs).resultType) {
+            switch (resultType) {
                 case PList:
                     calleeName = BuiltinNames.LIST;
                     break;

graalpython/lib-python/3/test/test_genexps.py

@@ -127,9 +127,11 @@
     [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]
 
 Verify re-use of tuples (a side benefit of using genexps over listcomps)
+(Note: CPython keeps a free list of small tuples and reuses them.
+This CPython specific optimization check is skipped in GraalPython.)
 
     >>> tupleids = list(map(id, ((i,i) for i in range(10))))
-    >>> int(max(tupleids) - min(tupleids))
+    >>> int(max(tupleids) - min(tupleids)) # doctest: +SKIP
     0
 
 Verify that syntax error's are raised for genexps used as lvalues