Stop injecting coverage hash fn definition in interfaces (#383)

lib/parse.js

@@ -51,8 +51,10 @@ parse.ContractDefinition = function(contract, expression) {
 };
 
 parse.ContractOrLibraryStatement = function(contract, expression) {
+
   // We need to define a method to pass coverage hashes into at top of each contract.
   // This lets us get a fresh stack for the hash and avoid stack-too-deep errors.
+  if (expression.kind !== 'interface'){
     const start = expression.range[0];
     const end = contract.instrumented.slice(expression.range[0]).indexOf('{') + 1;
     const loc = start + end;;
@@ -60,6 +62,7 @@ parse.ContractOrLibraryStatement = function(contract, expression) {
     (contract.injectionPoints[loc])
       ? contract.injectionPoints[loc].push({ type: 'injectHashMethod'})
       : contract.injectionPoints[loc] = [{ type: 'injectHashMethod'}];
+  }
 
   if (expression.subNodes) {
     expression.subNodes.forEach(construct => {

test/sources/solidity/contracts/statements/interface.sol

@@ -0,0 +1,12 @@
+pragma solidity ^0.5.8;
+
+interface IInterface {
+    event Assign(address indexed token, address indexed from, address indexed to, uint256 amount);
+    event Withdraw(address indexed token, address indexed from, address indexed to, uint256 amount);
+
+    // TODO: remove init from the interface, all the initialization should be outside the court
+    function init(address _owner) external;
+
+    function assign(uint _token, address _to, uint256 _amount) external;
+    function withdraw(uint _token, address _to, uint256 _amount) external;
+}

test/units/statements.js

@@ -53,6 +53,11 @@ describe('generic statements', () => {
     util.report(info.solcOutput.errors);
   });
 
+  it('should instrument an interface contract', () => {
+    const info = util.instrumentAndCompile('statements/interface');
+    util.report(info.solcOutput.errors);
+  })
+
   it('should NOT pass tests if the contract has a compilation error', () => {
     const info = util.instrumentAndCompile('app/SimpleError');
     try {