Mark the empty version pragma as invalid

liblangutil/SemVerHandler.cpp

@@ -151,6 +151,9 @@ optional<SemVerMatchExpression> SemVerMatchExpressionParser::parse()
 {
 	reset();
 
+	if (m_tokens.empty())
+		return nullopt;
+
 	try
 	{
 		while (true)

liblangutil/SemVerHandler.h

@@ -24,6 +24,7 @@
 #pragma once
 
 #include <liblangutil/Token.h>
+#include <libsolutil/Assertions.h>
 
 #include <string>
 #include <optional>
@@ -86,7 +87,9 @@ class SemVerMatchExpressionParser
 public:
 	SemVerMatchExpressionParser(std::vector<Token> _tokens, std::vector<std::string> _literals):
 		m_tokens(std::move(_tokens)), m_literals(std::move(_literals))
-	{}
+	{
+		solAssert(m_tokens.size() == m_literals.size(), "");
+	}
 
 	/// Returns an expression if it was parseable, or nothing otherwise.
 	std::optional<SemVerMatchExpression> parse();

libsolidity/parsing/Parser.cpp

@@ -204,7 +204,7 @@ ASTPointer<PragmaDirective> Parser::parsePragmaDirective()
 	nodeFactory.markEndPosition();
 	expectToken(Token::Semicolon);
 
-	if (literals.size() >= 2 && literals[0] == "solidity")
+	if (literals.size() >= 1 && literals[0] == "solidity")
 	{
 		parsePragmaVersion(
 			nodeFactory.location(),

test/libsolidity/syntaxTests/pragma/empty_version.sol

@@ -0,0 +1,3 @@
+pragma solidity;
+// ----
+// ParserError 1684: (0-16): Found version pragma, but failed to parse it. Please ensure there is a trailing semicolon.