Improves address literal checksum error message

Changelog.md

@@ -2,6 +2,7 @@
 
 Features:
  * Syntax Checker: Turn the usage of ``callcode`` into an error as experimental 0.5.0 feature.
+ * Type Checker: Improve address checksum warning.
  * Type Checker: More detailed errors for invalid array lengths (such as division by zero).
 
 Bugfixes:

libdevcore/CommonData.cpp

@@ -86,20 +86,23 @@ bool dev::passesAddressChecksum(string const& _str, bool _strict)
 	))
 		return true;
 
+	return _str == dev::getChecksummedAddress(_str);
+}
+
+string dev::getChecksummedAddress(string const& _addr)
+{
+	string s = _addr.substr(0, 2) == "0x" ? _addr.substr(2) : _addr;
 	h256 hash = keccak256(boost::algorithm::to_lower_copy(s, std::locale::classic()));
-	for (size_t i = 0; i < 40; ++i)
+	string ret = "0x";
+
+	for (size_t i = 0; i < s.length(); ++i)
 	{
 		char addressCharacter = s[i];
-		bool lowerCase;
-		if ('a' <= addressCharacter && addressCharacter <= 'f')
-			lowerCase = true;
-		else if ('A' <= addressCharacter && addressCharacter <= 'F')
-			lowerCase = false;
-		else
-			continue;
 		unsigned nibble = (unsigned(hash[i / 2]) >> (4 * (1 - (i % 2)))) & 0xf;
-		if ((nibble >= 8) == lowerCase)
-			return false;
+		if (nibble >= 8)
+			ret += toupper(addressCharacter);
+		else
+			ret += tolower(addressCharacter);
 	}
-	return true;
+	return ret;
 }

libdevcore/CommonData.h

@@ -209,4 +209,8 @@ bool contains(T const& _t, V const& _v)
 /// are considered valid.
 bool passesAddressChecksum(std::string const& _str, bool _strict);
 
+/// @returns the checksummed version of an address
+/// @param hex strings that look like an address
+std::string getChecksummedAddress(std::string const& _addr);
+
 }

libsolidity/analysis/TypeChecker.cpp

@@ -2000,7 +2000,9 @@ void TypeChecker::endVisit(Literal const& _literal)
 			m_errorReporter.warning(
 				_literal.location(),
 				"This looks like an address but has an invalid checksum. "
-				"If this is not used as an address, please prepend '00'."
+				"If this is not used as an address, please prepend '00'. "
+				"Correct checksummed address: '" + _literal.getChecksummedAddress() + "'. "
+				"For more information please see https://solidity.readthedocs.io/en/develop/types.html#address-literals"
 			);
 	}
 	if (!_literal.annotation().type)

libsolidity/ast/AST.cpp

@@ -583,3 +583,9 @@ bool Literal::passesAddressChecksum() const
 	solAssert(isHexNumber(), "Expected hex number");
 	return dev::passesAddressChecksum(value(), true);
 }
+
+std::string Literal::getChecksummedAddress() const
+{
+	solAssert(isHexNumber(), "Expected hex number");
+	return dev::getChecksummedAddress(value());
+}

libsolidity/ast/AST.h

@@ -1613,6 +1613,8 @@ public:
 	bool looksLikeAddress() const;
 	/// @returns true if it passes the address checksum test.
 	bool passesAddressChecksum() const;
+	/// @returns the checksummed version of an address
+	std::string getChecksummedAddress() const;
 
 private:
 	Token::Value m_token;