Distinct identifiers and tokens for integer type and integer class

- Using the same name causes syntax ambiguities. It's also not allowed for user-defined classes and types.

liblangutil/Token.h

@@ -273,7 +273,8 @@ namespace solidity::langutil
 	K(Class, "class", 0)                                               \
 	K(Instantiation, "instantiation", 0)                               \
 	K(Word, "word", 0)                                                 \
-	K(Integer, "integer", 0)                                           \
+	K(IntegerType, "integer", 0)                                       \
+	K(Integer, "Integer", 0)                                           \
 	K(Itself, "itself", 0)                                             \
 	K(Void, "void", 0)                                                 \
 	K(Pair, "pair", 0)                                                 \
@@ -307,7 +308,7 @@ namespace TokenTraits
 	constexpr bool isElementaryTypeName(Token tok)
 	{
 		return (Token::Int <= tok && tok < Token::TypesEnd) ||
-			tok == Token::Word || tok == Token::Void || tok == Token::Integer ||
+			tok == Token::Word || tok == Token::Void || tok == Token::IntegerType ||
 			tok == Token::Pair || tok == Token::Unit || tok == Token::Fun;
 	}
 	constexpr bool isAssignmentOp(Token tok) { return Token::Assign <= tok && tok <= Token::AssignMod; }

libsolidity/experimental/analysis/TypeRegistration.cpp

@@ -73,7 +73,7 @@ bool TypeRegistration::visit(ElementaryTypeName const& _typeName)
 			return m_typeSystem.constructor(PrimitiveType::Pair);
 		case Token::Word:
 			return m_typeSystem.constructor(PrimitiveType::Word);
-		case Token::Integer:
+		case Token::IntegerType:
 			return m_typeSystem.constructor(PrimitiveType::Integer);
 		case Token::Bool:
 			return m_typeSystem.constructor(PrimitiveType::Bool);

libsolidity/experimental/ast/TypeSystemHelper.cpp

@@ -66,7 +66,7 @@ std::optional<TypeConstructor> experimental::typeConstructorFromToken(Analysis c
 		return typeSystem.builtinConstructor(BuiltinType::Pair);
 	case Token::Word:
 		return typeSystem.builtinConstructor(BuiltinType::Word);
-	case Token::Integer:
+	case Token::IntegerType:
 		return typeSystem.builtinConstructor(BuiltinType::Integer);
 	case Token::Bool:
 		return typeSystem.builtinConstructor(BuiltinType::Bool);

test/libsolidity/semanticTests/experimental/stub.sol

@@ -34,7 +34,7 @@ instantiation word: * {
     }
 }
 
-instantiation word: integer {
+instantiation word: Integer {
     function fromInteger(x:integer) -> word {
         //x + x;
     }