Fix issue 150

numba_rvsdg/core/datastructures/ast_transforms.py

@@ -190,7 +190,7 @@ def prune_empty(self) -> set[WritableASTBlock]:
         """Prune empty blocks from the CFG."""
         empty = set()
         for name, block in list(self.items()):
-            if not block.instructions:
+            if not block.instructions and name != "0":
                 empty.add(self.pop(name))
                 # Empty blocks can only have a single jump target.
                 it = block.jump_targets[0]
@@ -724,6 +724,9 @@ def codegen(self, block: Any) -> MutableSequence[ast.AST]:
                 )
                 if_node = ast.If(test, body, orelse)
                 return block.tree[:-1] + [if_node]
+            elif block.fallthrough and len(block.tree) == 0:
+                # Am empty block, do nothing.
+                return [ast.Pass()]
             elif block.fallthrough and type(block.tree[-1]) is ast.Return:
                 # The value of the ast.Return could be either None or an
                 # ast.AST type. In the case of None, this refers to a plain

numba_rvsdg/tests/test_ast_transforms.py

@@ -616,7 +616,33 @@ def function() -> int:
                 "name": "6",
             },
         }
-        self.compare(function, expected, empty={"4", "7"})
+        self.compare(function, expected, empty={"7", "4"})
+
+    def test_if_in_while_without_else(self):
+        def function(i) -> int:
+            while i < 10:
+                i += 1
+            return i
+
+        expected = {
+            "0": {"instructions": [], "jump_targets": ["1"], "name": "0"},
+            "1": {
+                "instructions": ["i < 10"],
+                "jump_targets": ["2", "3"],
+                "name": "1",
+            },
+            "2": {
+                "instructions": ["i += 1"],
+                "jump_targets": ["1"],
+                "name": "2",
+            },
+            "3": {
+                "instructions": ["return i"],
+                "jump_targets": [],
+                "name": "3",
+            },
+        }
+        self.compare(function, expected, empty={"4"}, arguments=[(0,)])
 
     def test_while_in_if(self):
         def function(y: int) -> int: