Use Rc<str> instead of string. (#52)

This reduces std::mem::size_of::<Value>() to 16 bytes.
String values are also efficiently copied like Objects, arrays, sets etc.

When multiple function rules are evaluated, ensure that constant argument values
match before running the rule. If actual parameter does not match the constant parameter,
then the rule is skipped.

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

src/builtins/encoding.rs

@@ -29,7 +29,7 @@ fn base64_decode(span: &Span, params: &[Ref<Expr>], args: &[Value]) -> Result<Va
     let encoded_str = ensure_string(name, &params[0], &args[0])?;
     let decoded_bytes = BASE64.decode(encoded_str.as_bytes())?;
     Ok(Value::String(
-        String::from_utf8_lossy(&decoded_bytes).to_string(),
+        String::from_utf8_lossy(&decoded_bytes).into(),
     ))
 }
 
@@ -46,7 +46,8 @@ fn yaml_marshal(span: &Span, params: &[Ref<Expr>], args: &[Value]) -> Result<Val
     ensure_args_count(span, name, params, args, 1)?;
     Ok(Value::String(
         serde_yaml::to_string(&args[0])
-            .with_context(|| span.error("could not serialize to yaml"))?,
+            .with_context(|| span.error("could not serialize to yaml"))?
+            .into(),
     ))
 }
 
@@ -70,7 +71,8 @@ fn json_marshal(span: &Span, params: &[Ref<Expr>], args: &[Value]) -> Result<Val
     ensure_args_count(span, name, params, args, 1)?;
     Ok(Value::String(
         serde_json::to_string(&args[0])
-            .with_context(|| span.error("could not serialize to json"))?,
+            .with_context(|| span.error("could not serialize to json"))?
+            .into(),
     ))
 }