plus-equal-cost-more-for-state-variables

README.md

@@ -133,6 +133,7 @@ use-prefix-increment-not-postfix | The prefix increment expression is cheaper in
 use-short-revert-string | Shortening revert strings to fit in 32 bytes will decrease gas costs for deployment and gas costs when the revert condition has been met.
 non-payable-constructor | Consider making costructor payable to save gas.
 non-optimal-variables-swap | Consider swapping variables using `($VAR1, $VAR2) = ($VAR2, $VAR1)` to save gas.
+inefficient-state-variable-increment | <x> += <y> costs more gas than <x> = <x> + <y> for state variables.
 
 ## Best Practices Rules
 

solidity/performance/inefficient-state-variable-increment.sol

@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.2;
+
+contract A {
+ uint256[10] public a;
+ uint256 public b;
+ function one() public {
+ a[0] = 4;
+ b = 5;
+ // ruleid: inefficient-state-variable-increment
+ a[0] += b;
+ }
+}
+
+
+contract B {
+ uint256 public a;
+ uint256 public b;
+ function one() public {
+ a = 4;
+ b = 5;
+ // ok: inefficient-state-variable-increment
+ a = a + b;
+ }
+}
+
+contract C {
+ uint256 public a = 4;
+ uint256 public b;
+ function one() public {
+ b = 5;
+ // ruleid: inefficient-state-variable-increment
+ a += b;
+ }
+}
+
+contract D {
+ function one() public {
+ a = 4;
+ b = 5;
+ // ok: inefficient-state-variable-increment
+ a += b;
+ }
+}
+
+contract E {
+ mapping (address => uint) public a;
+ function one() public {
+ // ok: inefficient-state-variable-increment
+ a[msg.sender] += 4;
+ }
+}

solidity/performance/inefficient-state-variable-increment.yaml

@@ -0,0 +1,37 @@
+rules:
+ -
+ id: inefficient-state-variable-increment
+ message: |
+ <x> += <y> costs more gas than <x> = <x> + <y> for state variables.
+ metadata:
+ references:
+ - https://gist.github.com/IllIllI000/cbbfb267425b898e5be734d4008d4fe8
+ category: performance
+ tags:
+ - plus-equal
+ patterns:
+ - pattern-either:
+ - pattern: |
+ $X += $Y
+ - pattern: |
+ $X[...] += $Y
+ - pattern-either:
+ - pattern-inside: |
+ contract $C {
+ ...
+ $TYPE $X;
+ ...
+ }
+ - pattern-inside: |
+ contract $C {
+ ...
+ $TYPE $X = ...;
+ ...
+ }
+ - metavariable-regex:
+ metavariable: $TYPE
+ regex: uint
+ languages: 
+ - solidity
+ severity: INFO
+