Merge pull request #38 from codewithzubair07/feat/uint8-vs-uint256-solidity-rule

feat(solidity): add uint8 vs uint256 gas optimization rule

Author: mijinummi

packages/rules/src/solidity/mod.rs

@@ -0,0 +1,2 @@
+pub mod parser;
+pub mod uint8_vs_uint256;

packages/rules/src/solidity/uint8_vs_uint256.rs

@@ -0,0 +1,40 @@
+use crate::rule_engine::{Rule, RuleResult};
+use crate::solidity::parser::SolidityASTNode;
+
+pub struct Uint8VsUint256Rule;
+
+impl Rule for Uint8VsUint256Rule {
+    fn id(&self) -> &'static str {
+        "uint8-vs-uint256"
+    }
+
+    fn description(&self) -> &'static str {
+        "Using uint8 outside structs is often more gas-expensive than uint256 on EVM chains."
+    }
+
+    fn analyze(&self, ast: &SolidityASTNode) -> Vec<RuleResult> {
+        let mut results = Vec::new();
+
+        ast.walk(|node, parent| {
+            // Match variable declarations
+            if let SolidityASTNode::VariableDeclaration { type_name, location } = node {
+                // Only uint8
+                if type_name == "uint8" {
+                    // Ignore struct members
+                    if matches!(parent, Some(SolidityASTNode::StructDefinition { .. })) {
+                        return;
+                    }
+
+                    results.push(RuleResult {
+                        rule_id: self.id(),
+                        message: "uint8 used outside a struct. Consider using uint256 for better gas efficiency.".to_string(),
+                        location: location.clone(),
+                        severity: "LOW",
+                    });
+                }
+            }
+        });
+
+        results
+    }
+}