try to compil with the latest evm version if bytecode doesn't match

apps/explorer/lib/explorer/smart_contract/verifier.ex

@@ -28,7 +28,25 @@ defmodule Explorer.SmartContract.Verifier do
     solc_output =
       CodeCompiler.run(name, compiler_version, contract_source_code, optimization, evm_version, external_libraries)
 
-    compare_bytecodes(solc_output, address_hash, constructor_arguments)
+    case compare_bytecodes(solc_output, address_hash, constructor_arguments) do
+      {:error, :generated_bytecode} ->
+        next_evm_version = next_evm_version(evm_version)
+
+        second_solc_output =
+          CodeCompiler.run(
+            name,
+            compiler_version,
+            contract_source_code,
+            optimization,
+            next_evm_version,
+            external_libraries
+          )
+
+        compare_bytecodes(second_solc_output, address_hash, constructor_arguments)
+
+      result ->
+        result
+    end
   end
 
   defp compare_bytecodes({:error, :name}, _, _), do: {:error, :name}
@@ -71,4 +89,17 @@ defmodule Explorer.SmartContract.Verifier do
 
     bytecode
   end
+
+  def next_evm_version(current_evm_version) do
+    [prev_version, last_version] =
+      CodeCompiler.allowed_evm_versions()
+      |> Enum.reverse()
+      |> Enum.take(2)
+
+    if current_evm_version != last_version do
+      last_version
+    else
+      prev_version
+    end
+  end
 end

apps/explorer/test/explorer/smart_contract/verifier_test.exs

@@ -82,6 +82,41 @@ defmodule Explorer.SmartContract.VerifierTest do
       assert abi != nil
     end
 
+    test "tries to compile with the latest evm version if wrong evm version was provided" do
+      bytecode =
+        "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"
+
+      contract_address = insert(:contract_address, contract_code: bytecode)
+
+      code = """
+      pragma solidity ^0.4.15;
+      contract Incrementer {
+          event Incremented(address indexed sender, uint256 newValue);
+          uint256 public value;
+          address public lastSender;
+          function Incrementer(uint256 initialValue) {
+              value = initialValue;
+              lastSender = msg.sender;
+          }
+          function inc(uint256 delta) {
+              value = value + delta;
+              lastSender = msg.sender;
+          }
+      }
+      """
+
+      params = %{
+        "contract_source_code" => code,
+        "compiler_version" => "v0.4.15+commit.bbb8e64f",
+        "evm_version" => "homestead",
+        "name" => "Incrementer",
+        "optimization" => false
+      }
+
+      assert {:ok, %{abi: abi}} = Verifier.evaluate_authenticity(contract_address.hash, params)
+      assert abi != nil
+    end
+
     test "returns error when constructor arguments do not match", %{
       contract_code_info: contract_code_info
     } do