(valence_nbt) Add reverse From<Value> for Option<T> (#122)

This way we can use generic bounds to specify the return type and get `None` if the value does not match the type.

valence_nbt/src/value.rs

@@ -234,3 +234,123 @@ impl From<Vec<Vec<i64>>> for List {
         List::LongArray(v)
     }
 }
+
+impl From<Value> for Option<i8> {
+    fn from(value: Value) -> Self {
+        if let Value::Byte(b) = value {
+            Some(b)
+        } else {
+            None
+        }
+    }
+}
+
+impl From<Value> for Option<i16> {
+    fn from(value: Value) -> Self {
+        if let Value::Short(val) = value {
+            Some(val)
+        } else {
+            None
+        }
+    }
+}
+
+impl From<Value> for Option<i32> {
+    fn from(value: Value) -> Self {
+        if let Value::Int(val) = value {
+            Some(val)
+        } else {
+            None
+        }
+    }
+}
+
+impl From<Value> for Option<i64> {
+    fn from(value: Value) -> Self {
+        if let Value::Long(val) = value {
+            Some(val)
+        } else {
+            None
+        }
+    }
+}
+
+impl From<Value> for Option<f32> {
+    fn from(value: Value) -> Self {
+        if let Value::Float(val) = value {
+            Some(val)
+        } else {
+            None
+        }
+    }
+}
+
+impl From<Value> for Option<f64> {
+    fn from(value: Value) -> Self {
+        if let Value::Double(val) = value {
+            Some(val)
+        } else {
+            None
+        }
+    }
+}
+
+impl From<Value> for Option<Vec<i8>> {
+    fn from(value: Value) -> Self {
+        if let Value::ByteArray(val) = value {
+            Some(val)
+        } else {
+            None
+        }
+    }
+}
+
+impl From<Value> for Option<String> {
+    fn from(value: Value) -> Self {
+        if let Value::String(val) = value {
+            Some(val)
+        } else {
+            None
+        }
+    }
+}
+
+impl From<Value> for Option<List> {
+    fn from(value: Value) -> Self {
+        if let Value::List(val) = value {
+            Some(val)
+        } else {
+            None
+        }
+    }
+}
+
+impl From<Value> for Option<Compound> {
+    fn from(value: Value) -> Self {
+        if let Value::Compound(val) = value {
+            Some(val)
+        } else {
+            None
+        }
+    }
+}
+
+impl From<Value> for Option<Vec<i32>> {
+    fn from(value: Value) -> Self {
+        if let Value::IntArray(val) = value {
+            Some(val)
+        } else {
+            None
+        }
+    }
+}
+
+impl From<Value> for Option<Vec<i64>> {
+    fn from(value: Value) -> Self {
+        if let Value::LongArray(val) = value {
+            Some(val)
+        } else {
+            None
+        }
+    }
+}