Address comment: Simplify checkings in DecimalHaveSameScale

Author: zanmato1984

cpp/src/arrow/compute/kernel.cc

@@ -485,13 +485,11 @@ std::shared_ptr<MatchConstraint> DecimalsHaveSameScale() {
       DCHECK_GE(types.size(), 2);
       DCHECK(std::all_of(types.begin(), types.end(),
                          [](const TypeHolder& type) { return is_decimal(type.id()); }));
-      auto ty0 = checked_cast<const DecimalType*>(types[0].type);
-      DCHECK_NE(ty0, nullptr);
-      auto s0 = ty0->scale();
+      const auto& ty0 = checked_cast<const DecimalType&>(*types[0].type);
+      auto s0 = ty0.scale();
       for (size_t i = 1; i < types.size(); ++i) {
-        auto ty = checked_cast<const DecimalType*>(types[i].type);
-        DCHECK_NE(ty, nullptr);
-        if (ty->scale() != s0) {
+        const auto& ty = checked_cast<const DecimalType&>(*types[i].type);
+        if (ty.scale() != s0) {
           return false;
         }
       }
@@ -511,11 +509,9 @@ class BinaryDecimalScaleComparisonConstraint : public MatchConstraint {
     DCHECK_EQ(types.size(), 2);
     DCHECK(is_decimal(types[0].id()));
     DCHECK(is_decimal(types[1].id()));
-    auto ty0 = checked_cast<const DecimalType*>(types[0].type);
-    DCHECK_NE(ty0, nullptr);
-    auto ty1 = checked_cast<const DecimalType*>(types[1].type);
-    DCHECK_NE(ty1, nullptr);
-    return Op{}(ty0->scale(), ty1->scale());
+    const auto& ty0 = checked_cast<const DecimalType&>(*types[0].type);
+    const auto& ty1 = checked_cast<const DecimalType&>(*types[1].type);
+    return Op{}(ty0.scale(), ty1.scale());
   }
 };
 
@@ -580,9 +576,9 @@ bool KernelSignature::MatchesInputs(const std::vector<TypeHolder>& types) const
         return false;
       }
     }
-    if (constraint_ && !constraint_->Matches(types)) {
-      return false;
-    }
+  }
+  if (constraint_ && !constraint_->Matches(types)) {
+    return false;
   }
   return true;
 }