draft v2

lib/rules/gas-consumption/_gas-struct-packing.js

@@ -0,0 +1,149 @@
+/* eslint-disable */
+const BaseChecker = require('../base-checker')
+
+const ruleId = 'gas-struct-packing'
+const meta = {
+  type: 'gas-consumption',
+
+  docs: {
+    description: 'Suggest to re-arrange struct packing order when it is inefficient',
+    category: 'Gas Consumption Rules',
+    notes: [
+      {
+        note: 'This rule ',
+      },
+      {
+        note: '[source 1](https://coinsbench.com/comprehensive-guide-tips-and-tricks-for-gas-optimization-in-solidity-5380db734404) of the rule initiative (Variable Packing)',
+      },
+      {
+        note: '[source 2](https://www.rareskills.io/post/gas-optimization?postId=c9db474a-ff97-4fa3-a51d-fe13ccb8fe3b#viewer-f8m1r) of the rule initiative',
+      },
+    ],
+  },
+
+  isDefault: false,
+  recommended: false,
+  defaultSetup: 'warn',
+
+  schema: null,
+}
+
+class GasStructPacking extends BaseChecker {
+  constructor(reporter) {
+    super(reporter, ruleId, meta)
+  }
+
+  StructDefinition(node) {
+    if (this.isInefficientlyPacked(node)) {
+      this.reportError(node)
+    }
+  }
+
+  isInefficientlyPacked(structNode) {
+    if (!structNode || !Array.isArray(structNode.members)) {
+      return false
+    }
+
+    let members = structNode.members.map((member) => ({
+      name: member.name,
+      size: this.getVariableSize(member.typeName),
+      type: member.typeName.type,
+    }))
+
+    let currentSlotSize = 0
+    let potentialSavings = 0
+    let dynamicTypeEncountered = false
+
+    for (const member of members) {
+      // Dynamically-sized types (strings, arrays) and mappings always start a new slot.
+      if (this.isDynamicType(member.type)) {
+        currentSlotSize = 0
+        dynamicTypeEncountered = true
+        continue
+      }
+
+      if (member.size === 32 || dynamicTypeEncountered) {
+        currentSlotSize = 0
+        dynamicTypeEncountered = false
+      }
+
+      if (currentSlotSize + member.size > 32) {
+        potentialSavings += 32 - currentSlotSize
+        currentSlotSize = member.size
+      } else {
+        currentSlotSize += member.size
+      }
+    }
+
+    if (currentSlotSize > 0 && currentSlotSize < 32) {
+      potentialSavings += 32 - currentSlotSize
+    }
+
+    return potentialSavings > 0
+  }
+
+  isDynamicType(typeNode) {
+    if (!typeNode) {
+      return false
+    }
+
+    switch (typeNode.type) {
+      case 'Mapping':
+        // Mappings are always dynamically sized
+        return true
+      case 'ArrayTypeName':
+        // Arrays are dynamically sized unless they have a fixed size declared
+        return !typeNode.length
+      case 'ElementaryTypeName':
+        // Strings and bytes are dynamically sized elementary types
+        if (typeNode.name.startsWith('string') || typeNode.name.startsWith('bytes')) {
+          return true
+        }
+        break
+      case 'UserDefinedTypeName':
+        // For user-defined types, more complex logic might be required
+        // to determine if they are dynamically sized. This could involve
+        // looking up their definitions if available.
+        // For now, let's assume they are not dynamically sized.
+        return false
+      // ... handle any other specific types as needed ...
+    }
+
+    return false // Default to false if type is not recognized as dynamic
+  }
+
+  getVariableSize(typeNode) {
+    // Enhanced version to handle more types
+    switch (typeNode.type) {
+      case 'ElementaryTypeName':
+        switch (typeNode.name) {
+          case 'address':
+            return 20 // Address is 20 bytes
+          case 'bool':
+            return 1 // Bool is 1 byte
+          case 'uint256':
+          case 'int256':
+            return 32 // uint256 and int256 are 32 bytes
+          // ...other elementary types...
+        }
+        break
+      case 'UserDefinedTypeName':
+        // For user-defined types, you might assume worst-case (full slot usage)
+        // unless you analyze their definitions as well.
+        return 32
+      // ...cases for arrays, mappings, etc...
+    }
+
+    return 32 // Default to 32 bytes for unknown or complex types
+  }
+
+  reportError(node) {
+    // const variableName = fullVariableName.split('.')[0]
+    this.error(
+      node,
+      `GC: For [ ] struct, packing seems inefficient. Try rearranging variables to achieve 32bytes slots`
+    )
+  }
+}
+
+module.exports = GasStructPacking