Added error for when "require MONITOR" instead of "require monitor MO…

…NITOR"

src/scenic/core/dynamics/scenarios.py

@@ -1,5 +1,6 @@
 """Dynamic scenarios."""
 
+import ast
 from collections import defaultdict
 import dataclasses
 import functools
@@ -8,8 +9,9 @@
 
 import rv_ltl
 
+import scenic
 import scenic.core.dynamics as dynamics
-from scenic.core.errors import InvalidScenarioError
+from scenic.core.errors import InvalidScenarioError, ScenicSyntaxError
 from scenic.core.lazy_eval import DelayedArgument, needsLazyEvaluation
 from scenic.core.requirements import (
     DynamicRequirement,
@@ -429,6 +431,23 @@ def _compileRequirements(self):
         assert requirementSyntax is not None
         for reqID, requirement in self._pendingRequirements.items():
             syntax = requirementSyntax[reqID] if requirementSyntax else None
+
+            # Catch the simple case where someone has most likely forgotten the "monitor"
+            # keyword.
+            if (
+                (not requirement.ty == RequirementType.monitor)
+                and isinstance(syntax, ast.Call)
+                and isinstance(syntax.func, ast.Name)
+                and syntax.func.id in namespace
+                and isinstance(namespace[syntax.func.id], type)
+                and issubclass(
+                    namespace[syntax.func.id], scenic.core.dynamics.behaviors.Monitor
+                )
+            ):
+                raise ScenicSyntaxError(
+                    f"Missing 'monitor' keyword after 'require' when instantiating '{syntax.func.id}'"
+                )
+
             compiledReq = requirement.compile(namespace, self, syntax)
 
             self._registerCompiledRequirement(compiledReq)

tests/syntax/test_dynamics.py

@@ -1466,6 +1466,18 @@ def test_require_monitor_invalid():
         sampleScene(scenario)
 
 
+def test_require_monitor_error():
+    with pytest.raises(ScenicSyntaxError):
+        compileScenic(
+            """
+            monitor Monitor():
+                wait
+            ego = new Object
+            require Monitor()
+        """
+        )
+
+
 def test_old_style_monitor():
     with pytest.raises(ScenicSyntaxError):
         compileScenic(