[MLIR][Python] Fix detached operation coming from IfOp constructor (#107286)

Without this fix, `scf.if` operations would be created without a parent.
Since `scf.if` operations often have no results, this caused silent bugs
where the generated code was straight-up missing the operation.

mlir/python/mlir/dialects/scf.py

@@ -87,7 +87,7 @@ class IfOp(IfOp):
         operands.append(cond)
         results = []
         results.extend(results_)
-        super().__init__(results, cond)
+        super().__init__(results, cond, loc=loc, ip=ip)
         self.regions[0].blocks.append(*[])
         if hasElse:
             self.regions[1].blocks.append(*[])

mlir/test/python/dialects/scf.py

@@ -278,6 +278,32 @@ def testIfWithoutElse():
 # CHECK: return
 
 
+@constructAndPrintInModule
+def testNestedIf():
+    bool = IntegerType.get_signless(1)
+    i32 = IntegerType.get_signless(32)
+
+    @func.FuncOp.from_py_func(bool, bool)
+    def nested_if(b, c):
+        if_op = scf.IfOp(b)
+        with InsertionPoint(if_op.then_block) as ip:
+            if_op = scf.IfOp(c, ip=ip)
+            with InsertionPoint(if_op.then_block):
+                one = arith.ConstantOp(i32, 1)
+                add = arith.AddIOp(one, one)
+                scf.YieldOp([])
+            scf.YieldOp([])
+        return
+
+
+# CHECK: func @nested_if(%[[ARG0:.*]]: i1, %[[ARG1:.*]]: i1)
+# CHECK: scf.if %[[ARG0:.*]]
+# CHECK:   scf.if %[[ARG1:.*]]
+# CHECK:     %[[ONE:.*]] = arith.constant 1
+# CHECK:     %[[ADD:.*]] = arith.addi %[[ONE]], %[[ONE]]
+# CHECK: return
+
+
 @constructAndPrintInModule
 def testIfWithElse():
     bool = IntegerType.get_signless(1)