[mlir][python] Add bindings for diagnostic handler.

I considered multiple approaches for this but settled on this one because I could make the lifetime management work in a reasonably easy way (others had issues with not being able to cast to a Python reference from a C++ constructor). We could stand to have more formatting helpers, but best to get the core mechanism in first.

Differential Revision: https://reviews.llvm.org/D116568

mlir/python/mlir/_mlir_libs/_mlir/ir.pyi

@@ -7,7 +7,7 @@
 #   * Local edits to signatures and types that MyPy did not auto detect (or
 #     detected incorrectly).
 
-from typing import Any, Callable, ClassVar, Dict, List, Optional, Sequence
+from typing import Any, Callable, ClassVar, Dict, List, Optional, Sequence, Tuple
 
 from typing import overload
 
@@ -43,6 +43,9 @@ __all__ = [
     "Dialect",
     "DialectDescriptor",
     "Dialects",
+    "Diagnostic",
+    "DiagnosticHandler",
+    "DiagnosticSeverity",
     "DictAttr",
     "F16Type",
     "F32Type",
@@ -425,8 +428,9 @@ class Context:
     def _get_live_count() -> int: ...
     def _get_live_module_count(self) -> int: ...
     def _get_live_operation_count(self) -> int: ...
+    def attach_diagnostic_handler(self, callback: Callable[["Diagnostic"], bool]) -> "DiagnosticHandler": ...
     def enable_multithreading(self, enable: bool) -> None: ...
-    def get_dialect_descriptor(name: dialect_name: str) -> "DialectDescriptor": ...
+    def get_dialect_descriptor(dialect_name: str) -> "DialectDescriptor": ...
     def is_registered_operation(self, operation_name: str) -> bool: ...
     def __enter__(self) -> "Context": ...
     def __exit__(self, arg0: object, arg1: object, arg2: object) -> None: ...
@@ -479,6 +483,31 @@ class Dialects:
     def __getattr__(self, arg0: str) -> "Dialect": ...
     def __getitem__(self, arg0: str) -> "Dialect": ...
 
+class Diagnostic:
+    @property
+    def severity(self) -> "DiagnosticSeverity": ...
+    @property
+    def location(self) -> "Location": ...
+    @property
+    def message(self) -> str: ...
+    @property
+    def notes(self) -> Tuple["Diagnostic"]: ...
+
+class DiagnosticHandler:
+    def detach(self) -> None: ...
+    @property
+    def attached(self) -> bool: ...
+    @property
+    def had_error(self) -> bool: ...
+    def __enter__(self) -> "DiagnosticHandler": ...
+    def __exit__(self, arg0: object, arg1: object, arg2: object) -> None: ...
+
+class DiagnosticSeverity:
+    ERROR: "DiagnosticSeverity"
+    WARNING: "DiagnosticSeverity"
+    NOTE: "DiagnosticSeverity"
+    REMARK: "DiagnosticSeverity"
+
 # TODO: Auto-generated. Audit and fix.
 class DictAttr(Attribute):
     def __init__(self, cast_from_attr: Attribute) -> None: ...