Adds an additional message to failing type conversions.

8 files changed, 34 insertions, 19 deletions

diff --git a/Changelog.md b/Changelog.md
index cf3cf9e2..6a366ca0 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -6,6 +6,7 @@ Language Features:
 Compiler Features:
  * Inline Assembly: Improve error messages around invalid function argument count.
  * Code Generator: Use binary search for dispatch function if more efficient. The size/speed tradeoff can be tuned using ``--optimize-runs``.
+ * Type Checker: Add an additional reason to be displayed when type conversion fails.
 
 
 Bugfixes:
diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
index 5c8e0c6c..1c9f1956 100644
--- a/libsolidity/analysis/TypeChecker.cpp
+++ b/libsolidity/analysis/TypeChecker.cpp
@@ -1252,7 +1252,8 @@ void TypeChecker::endVisit(BinaryOperation const& _operation)
 {
 	TypePointer const& leftType = type(_operation.leftExpression());
 	TypePointer const& rightType = type(_operation.rightExpression());
-	TypePointer commonType = leftType->binaryOperatorResult(_operation.getOperator(), rightType);
+	TypeResult result = leftType->binaryOperatorResult(_operation.getOperator(), rightType);
+	TypePointer commonType = result.get();
 	if (!commonType)
 	{
 		m_errorReporter.typeError(
@@ -1262,7 +1263,8 @@ void TypeChecker::endVisit(BinaryOperation const& _operation)
 			" not compatible with types " +
 			leftType->toString() +
 			" and " +
-			rightType->toString()
+			rightType->toString() +
+			(!result.message().empty() ? ". " + result.message() : "")
 		);
 		commonType = leftType;
 	}
diff --git a/libsolidity/ast/Types.cpp b/libsolidity/ast/Types.cpp
index fd8839ca..0822fb4a 100644
--- a/libsolidity/ast/Types.cpp
+++ b/libsolidity/ast/Types.cpp
@@ -512,9 +512,8 @@ TypeResult AddressType::unaryOperatorResult(Token _operator) const
 
 TypeResult AddressType::binaryOperatorResult(Token _operator, TypePointer const& _other) const
 {
-	// Addresses can only be compared.
 	if (!TokenTraits::isCompareOp(_operator))
-		return TypePointer();
+		return TypeResult{"Addresses can only be compared"};
 
 	return Type::commonType(shared_from_this(), _other);
 }
@@ -678,9 +677,8 @@ TypeResult IntegerType::binaryOperatorResult(Token _operator, TypePointer const&
 		return TypePointer();
 	if (auto intType = dynamic_pointer_cast<IntegerType const>(commonType))
 	{
-		// Signed EXP is not allowed
 		if (Token::Exp == _operator && intType->isSigned())
-			return TypePointer();
+			return TypeResult{"Signed exponentiation is not allowed"};
 	}
 	else if (auto fixType = dynamic_pointer_cast<FixedPointType const>(commonType))
 		if (Token::Exp == _operator)
@@ -1128,9 +1126,8 @@ TypeResult RationalNumberType::binaryOperatorResult(Token _operator, TypePointer
 
 				uint32_t absExp = bigint(abs(exp)).convert_to<uint32_t>();
 
-				// Limit size to 4096 bits
 				if (!fitsPrecisionExp(abs(m_value.numerator()), absExp) || !fitsPrecisionExp(abs(m_value.denominator()), absExp))
-					return TypePointer();
+					return TypeResult{"Precision is limited to 4096 bits"};
 
 				static auto const optimizedPow = [](bigint const& _base, uint32_t _exponent) -> bigint {
 					if (_base == 1)
@@ -1211,7 +1208,7 @@ TypeResult RationalNumberType::binaryOperatorResult(Token _operator, TypePointer
 
 		// verify that numerator and denominator fit into 4096 bit after every operation
 		if (value.numerator() != 0 && max(mostSignificantBit(abs(value.numerator())), mostSignificantBit(abs(value.denominator()))) > 4096)
-			return TypePointer();
+			return TypeResult{"Precision is limited to 4096 bits"};
 
 		return TypeResult(make_shared<RationalNumberType>(value));
 	}
diff --git a/test/libsolidity/syntaxTests/nameAndTypeResolution/201_integer_signed_exp_signed.sol b/test/libsolidity/syntaxTests/nameAndTypeResolution/201_integer_signed_exp_signed.sol
index 93e5f065..c2f930b7 100644
--- a/test/libsolidity/syntaxTests/nameAndTypeResolution/201_integer_signed_exp_signed.sol
+++ b/test/libsolidity/syntaxTests/nameAndTypeResolution/201_integer_signed_exp_signed.sol
@@ -1,3 +1,3 @@
 contract test { function() external { int x = -3; int y = -4; x ** y; } }
 // ----
-// TypeError: (62-68): Operator ** not compatible with types int256 and int256
+// TypeError: (62-68): Operator ** not compatible with types int256 and int256. Signed exponentiation is not allowed
diff --git a/test/libsolidity/syntaxTests/types/address/address_binary_operators.sol b/test/libsolidity/syntaxTests/types/address/address_binary_operators.sol
new file mode 100644
index 00000000..ab92ab36
--- /dev/null
+++ b/test/libsolidity/syntaxTests/types/address/address_binary_operators.sol
@@ -0,0 +1,15 @@
+contract C {
+    address a;
+    function f() public pure returns(bool) {
+        a = address(0) + address(0);
+        a = address(0) - address(0);
+        a = address(0) * address(0);
+        a = address(0) / address(0);
+        return address(0) == address(0);
+    }
+}
+// ----
+// TypeError: (85-108): Operator + not compatible with types address payable and address payable. Addresses can only be compared
+// TypeError: (122-145): Operator - not compatible with types address payable and address payable. Addresses can only be compared
+// TypeError: (159-182): Operator * not compatible with types address payable and address payable. Addresses can only be compared
+// TypeError: (196-219): Operator / not compatible with types address payable and address payable. Addresses can only be compared
diff --git a/test/libsolidity/syntaxTests/types/rational_number_div_limit.sol b/test/libsolidity/syntaxTests/types/rational_number_div_limit.sol
index 1b0b5f94..71b736b8 100644
--- a/test/libsolidity/syntaxTests/types/rational_number_div_limit.sol
+++ b/test/libsolidity/syntaxTests/types/rational_number_div_limit.sol
@@ -5,5 +5,5 @@ contract c {
     }
 }
 // ----
-// TypeError: (71-92): Operator / not compatible with types rational_const 1 / 5221...(1225 digits omitted)...5168 and int_const 5221...(1225 digits omitted)...5168
+// TypeError: (71-92): Operator / not compatible with types rational_const 1 / 5221...(1225 digits omitted)...5168 and int_const 5221...(1225 digits omitted)...5168. Precision is limited to 4096 bits
 // TypeError: (71-92): Type rational_const 1 / 5221...(1225 digits omitted)...5168 is not implicitly convertible to expected type int256. Try converting to type ufixed8x80 or use an explicit conversion.
diff --git a/test/libsolidity/syntaxTests/types/rational_number_exp_limit_fail.sol b/test/libsolidity/syntaxTests/types/rational_number_exp_limit_fail.sol
index 058db2e9..d9f89119 100644
--- a/test/libsolidity/syntaxTests/types/rational_number_exp_limit_fail.sol
+++ b/test/libsolidity/syntaxTests/types/rational_number_exp_limit_fail.sol
@@ -19,23 +19,23 @@ contract c {
     }
 }
 // ----
-// TypeError: (71-102): Operator ** not compatible with types int_const 1797...(301 digits omitted)...7216 and int_const 4
+// TypeError: (71-102): Operator ** not compatible with types int_const 1797...(301 digits omitted)...7216 and int_const 4. Precision is limited to 4096 bits
 // TypeError: (71-102): Type int_const 1797...(301 digits omitted)...7216 is not implicitly convertible to expected type int256.
-// TypeError: (116-148): Operator ** not compatible with types int_const 1797...(301 digits omitted)...7216 and int_const 4
-// TypeError: (116-153): Operator ** not compatible with types int_const 1797...(301 digits omitted)...7216 and int_const 4
+// TypeError: (116-148): Operator ** not compatible with types int_const 1797...(301 digits omitted)...7216 and int_const 4. Precision is limited to 4096 bits
+// TypeError: (116-153): Operator ** not compatible with types int_const 1797...(301 digits omitted)...7216 and int_const 4. Precision is limited to 4096 bits
 // TypeError: (116-153): Type int_const 1797...(301 digits omitted)...7216 is not implicitly convertible to expected type int256.
 // TypeError: (167-203): Operator ** not compatible with types int_const 4 and int_const -179...(302 digits omitted)...7216
 // TypeError: (217-228): Operator ** not compatible with types int_const 2 and int_const 1000...(1226 digits omitted)...0000
 // TypeError: (242-254): Operator ** not compatible with types int_const -2 and int_const 1000...(1226 digits omitted)...0000
 // TypeError: (268-280): Operator ** not compatible with types int_const 2 and int_const -100...(1227 digits omitted)...0000
 // TypeError: (294-307): Operator ** not compatible with types int_const -2 and int_const -100...(1227 digits omitted)...0000
-// TypeError: (321-332): Operator ** not compatible with types int_const 1000...(1226 digits omitted)...0000 and int_const 2
+// TypeError: (321-332): Operator ** not compatible with types int_const 1000...(1226 digits omitted)...0000 and int_const 2. Precision is limited to 4096 bits
 // TypeError: (321-332): Type int_const 1000...(1226 digits omitted)...0000 is not implicitly convertible to expected type int256.
-// TypeError: (346-358): Operator ** not compatible with types int_const -100...(1227 digits omitted)...0000 and int_const 2
+// TypeError: (346-358): Operator ** not compatible with types int_const -100...(1227 digits omitted)...0000 and int_const 2. Precision is limited to 4096 bits
 // TypeError: (346-358): Type int_const -100...(1227 digits omitted)...0000 is not implicitly convertible to expected type int256.
-// TypeError: (372-384): Operator ** not compatible with types int_const 1000...(1226 digits omitted)...0000 and int_const -2
+// TypeError: (372-384): Operator ** not compatible with types int_const 1000...(1226 digits omitted)...0000 and int_const -2. Precision is limited to 4096 bits
 // TypeError: (372-384): Type int_const 1000...(1226 digits omitted)...0000 is not implicitly convertible to expected type int256.
-// TypeError: (398-411): Operator ** not compatible with types int_const -100...(1227 digits omitted)...0000 and int_const -2
+// TypeError: (398-411): Operator ** not compatible with types int_const -100...(1227 digits omitted)...0000 and int_const -2. Precision is limited to 4096 bits
 // TypeError: (398-411): Type int_const -100...(1227 digits omitted)...0000 is not implicitly convertible to expected type int256.
 // TypeError: (425-441): Operator ** not compatible with types int_const 1000...(1226 digits omitted)...0000 and int_const 1000...(1226 digits omitted)...0000
 // TypeError: (425-441): Type int_const 1000...(1226 digits omitted)...0000 is not implicitly convertible to expected type int256.
diff --git a/test/libsolidity/syntaxTests/types/rational_number_mul_limit.sol b/test/libsolidity/syntaxTests/types/rational_number_mul_limit.sol
index bbed94b5..487e7432 100644
--- a/test/libsolidity/syntaxTests/types/rational_number_mul_limit.sol
+++ b/test/libsolidity/syntaxTests/types/rational_number_mul_limit.sol
@@ -5,5 +5,5 @@ contract c {
     }
 }
 // ----
-// TypeError: (71-90): Operator * not compatible with types int_const 5221...(1225 digits omitted)...5168 and int_const 5221...(1225 digits omitted)...5168
+// TypeError: (71-90): Operator * not compatible with types int_const 5221...(1225 digits omitted)...5168 and int_const 5221...(1225 digits omitted)...5168. Precision is limited to 4096 bits
 // TypeError: (71-90): Type int_const 5221...(1225 digits omitted)...5168 is not implicitly convertible to expected type int256.