initial work on pattern matching classes

Author: juliandolby

core/com.ibm.wala.cast.python.test/data/match5.py

@@ -0,0 +1,37 @@
+class Nothing:
+    def act(self):
+        print("Nothing")
+
+
+def id(x):
+    return x
+
+
+class Something:
+    a = 0
+    b = 0
+
+    def __init__(self, a, b):
+        self.a = id(a)
+        self.b = id(b)
+
+    def act(self):
+        print(self.a + self.b)
+
+
+def doit(x):
+    match x:
+        case Nothing():
+            x.act()
+        case Something(a=5, b=7):
+            x.act()
+        case Something():
+            print("unexpected something")
+        case _:
+            print("unexpected value")
+
+
+doit(Nothing())
+doit(Something(5, 7))
+doit(Something(3, 4))
+doit(10)

jep/com.ibm.wala.cast.python.cpython/source/com/ibm/wala/cast/python/jep/ast/CPythonAstToCAstTranslator.java

@@ -2460,6 +2460,40 @@ public CAstNode matchVar() {
       return result;
     }
 
+    public CAstNode visitMatchClass(PyObject cls, WalkContext context) {
+      PyObject klass = cls.getAttr("cls", PyObject.class);
+      CAstNode result =
+          ast.makeNode(CAstNode.INSTANCEOF, visit(klass, context), context.matchVar());
+
+      @SuppressWarnings("unchecked")
+      Iterator<String> names = cls.getAttr("kwd_attrs", List.class).iterator();
+      @SuppressWarnings("unchecked")
+      Iterator<PyObject> patterns = cls.getAttr("kwd_patterns", List.class).iterator();
+      while (names.hasNext()) {
+        String name = names.next();
+        WalkContext eltContext =
+            new WalkContext() {
+
+              @Override
+              public WalkContext getParent() {
+                return context;
+              }
+
+              @Override
+              public CAstNode matchVar() {
+                return ast.makeNode(
+                    CAstNode.OBJECT_REF, context.matchVar(), ast.makeConstant(name));
+              }
+            };
+
+        CAstNode eltNode = visit(patterns.next(), eltContext);
+
+        result = ast.makeNode(CAstNode.IF_EXPR, result, eltNode, ast.makeConstant(false));
+      }
+
+      return result;
+    }
+
     private int nextDecl = 0;
 
     public CAstNode visitMatch(PyObject match, WalkContext context) {

jep/com.ibm.wala.cast.python.cpython/test/com/ibm/wala/cast/python/cpython/test/TestMatch.java

@@ -140,4 +140,39 @@ public void testMatch4()
 
     verifyGraphAssertions(CG, assertionsForMatch4);
   }
+
+  protected static final Object[][] assertionsForMatch5 =
+      new Object[][] {
+        new Object[] {ROOT, new String[] {"script match5.py"}},
+        new Object[] {"script match5.py", new String[] {"script match5.py/doit"}},
+        new Object[] {
+          "script match5.py/doit",
+          new String[] {
+            "$script match5.py/Nothing/act:trampoline1",
+            "$script match5.py/Something/act:trampoline1",
+          }
+        },
+        new Object[] {
+          "$script match5.py/Nothing/act:trampoline1", new String[] {"script match5.py/Nothing/act"}
+        },
+        new Object[] {
+          "$script match5.py/Something/act:trampoline1",
+          new String[] {"script match5.py/Something/act"}
+        }
+      };
+
+  @Test
+  public void testMatch5()
+      throws ClassHierarchyException, IllegalArgumentException, CancelException, IOException {
+    PythonAnalysisEngine<?> E = makeEngine("match5.py");
+    PythonSSAPropagationCallGraphBuilder B = E.defaultCallGraphBuilder();
+    CallGraph CG = B.makeCallGraph(B.getOptions());
+
+    System.err.println(CG);
+    CAstCallGraphUtil.AVOID_DUMP.set(false);
+    CAstCallGraphUtil.dumpCG(
+        (SSAContextInterpreter) B.getContextInterpreter(), B.getPointerAnalysis(), CG);
+
+    verifyGraphAssertions(CG, assertionsForMatch5);
+  }
 }