[mlir] Simplify folding code (NFC)

Author: akuegel

mlir/lib/Dialect/Complex/IR/ComplexOps.cpp

@@ -24,7 +24,7 @@ OpFoldResult ReOp::fold(ArrayRef<Attribute> operands) {
   ArrayAttr arrayAttr = operands[0].dyn_cast_or_null<ArrayAttr>();
   if (arrayAttr && arrayAttr.size() == 2)
     return arrayAttr[0];
-  if (auto createOp = dyn_cast_or_null<CreateOp>(getOperand().getDefiningOp()))
+  if (auto createOp = getOperand().getDefiningOp<CreateOp>())
     return createOp.getOperand(0);
   return {};
 }
@@ -34,7 +34,7 @@ OpFoldResult ImOp::fold(ArrayRef<Attribute> operands) {
   ArrayAttr arrayAttr = operands[0].dyn_cast_or_null<ArrayAttr>();
   if (arrayAttr && arrayAttr.size() == 2)
     return arrayAttr[1];
-  if (auto createOp = dyn_cast_or_null<CreateOp>(getOperand().getDefiningOp()))
+  if (auto createOp = getOperand().getDefiningOp<CreateOp>())
     return createOp.getOperand(1);
   return {};
 }