Fix Pyright complains from #535 and #536 (#539)

Fix Pyright complains from #535 and #536 (that removed`isinstance`
causing performance issue).
Casts to correct type so pyright doesn't complain

Author: zhenrongliew

src/kirin/dialects/scf/stmts.py

@@ -41,16 +41,16 @@ def __init__(
                 then_body_block = None
         else:  # then_body.IS_BLOCK:
             then_body_block = cast(Block, then_body)
-            then_body_region = Region(then_body)
+            then_body_region = cast(Region, then_body)
 
         if else_body is None:
             else_body_region = ir.Region()
             else_body_block = None
         elif else_body.IS_REGION:
             else_body_region = cast(Region, else_body)
-            if not else_body.blocks:  # empty region
+            if not else_body_region.blocks:  # empty region
                 else_body_block = None
-            elif len(else_body.blocks) == 0:
+            elif len(else_body_region.blocks) == 0:
                 else_body_block = None
             else:
                 else_body_block = else_body_region.blocks[0]
@@ -63,6 +63,7 @@ def __init__(
         results = ()
         if then_body_block is not None:
             then_yield = then_body_block.last_stmt
+            else_body_block = cast(Block, else_body_block)
             else_yield = (
                 else_body_block.last_stmt if else_body_block is not None else None
             )

src/kirin/lowering/frame.py

@@ -21,6 +21,7 @@
     from .state import State
 
 CallbackFn = Callable[["Frame", SSAValue], SSAValue]
+StmtType = TypeVar("StmtType", bound=Statement)
 
 
 @dataclass
@@ -53,8 +54,6 @@ class Frame(Generic[Stmt]):
     def __repr__(self):
         return f"Frame({len(self.defs)} defs, {len(self.globals)} globals)"
 
-    StmtType = TypeVar("StmtType", bound=Statement)
-
     @overload
     def push(self, node: StmtType) -> StmtType: ...
 
@@ -65,7 +64,7 @@ def push(self, node: StmtType | Block) -> StmtType | Block:
         if node.IS_BLOCK:
             return self._push_block(cast(Block, node))
         elif node.IS_STATEMENT:
-            return self._push_stmt(cast(Statement, node))
+            return self._push_stmt(cast(StmtType, node))
         else:
             raise BuildError(f"Unsupported type {type(node)} in push()")