src: fix warnings in aliased_buffer

* Unary minus usages on unsigned type
* Implicit casts to/from input parameters

PR-URL: #19665
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Khaidi Chu <i@2333.moe>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>

src/aliased_buffer.h

@@ -126,13 +126,11 @@ class AliasedBuffer {
           index_(that.index_) {
     }
 
-    template <typename T>
-    inline Reference& operator=(const T& val) {
+    inline Reference& operator=(const NativeT& val) {
       aliased_buffer_->SetValue(index_, val);
       return *this;
     }
 
-    // This is not caught by the template operator= above.
     inline Reference& operator=(const Reference& val) {
       return *this = static_cast<NativeT>(val);
     }
@@ -141,9 +139,8 @@ class AliasedBuffer {
       return aliased_buffer_->GetValue(index_);
     }
 
-    template <typename T>
-    inline Reference& operator+=(const T& val) {
-      const T current = aliased_buffer_->GetValue(index_);
+    inline Reference& operator+=(const NativeT& val) {
+      const NativeT current = aliased_buffer_->GetValue(index_);
       aliased_buffer_->SetValue(index_, current + val);
       return *this;
     }
@@ -152,9 +149,10 @@ class AliasedBuffer {
       return this->operator+=(static_cast<NativeT>(val));
     }
 
-    template <typename T>
-    inline Reference& operator-=(const T& val) {
-      return this->operator+=(-val);
+    inline Reference& operator-=(const NativeT& val) {
+      const NativeT current = aliased_buffer_->GetValue(index_);
+      aliased_buffer_->SetValue(index_, current - val);
+      return *this;
     }
 
    private: