Merge pull request #935 from chriseth/pragma

Version pragma

28 files changed, 906 insertions, 66 deletions

diff --git a/Changelog.md b/Changelog.md
index 5cf2898b..25890890 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -6,6 +6,9 @@ enforce some safety features. The most important change is
 
 Breaking Changes:
 
+ * Source files have to specify the compiler version they are
+   compatible with using e.g. `pragma solidity ^0.4.0;` or
+   `pragma solidity >=0.4.0 <0.4.8;`
  * Contracts that want to receive Ether have to implement a fallback
    function (contracts now throw if no fallback function is defined
    and no function matches the signature).
diff --git a/docs/layout-of-source-files.rst b/docs/layout-of-source-files.rst
index 6ef06961..fdb7b5e8 100644
--- a/docs/layout-of-source-files.rst
+++ b/docs/layout-of-source-files.rst
@@ -2,7 +2,36 @@
 Layout of a Solidity Source File
 ********************************
 
-Source files can contain an arbitrary number of contract definitions and include directives.
+Source files can contain an arbitrary number of contract definitions, include directives
+and pragma directives.
+
+.. index:: ! pragma, version
+
+Version Pragma
+==============
+
+Source files can (and should) be annotated with a so-called version pragma to reject
+being compiled with future compiler versions that might introduce incompatible
+changes. We try to keep such changes to an absolute minimum and especially
+introduce changes in a way that changes in semantics will also require changes
+in the syntax, but this is of course not always possible. Because of that, it is always
+a good idea to read through the changelog at least for releases that contain
+breaking changes, those releases will always have versions of the form
+``0.x.0`` or ``x.0.0``.
+
+The version pragma is used as follows::
+
+  pragma solidity ^0.4.0;
+
+Such a source file will not compile with a compiler earlier than version 0.4.0
+and it will also not work on a compiler starting form version 0.5.0 (this
+second condition is added by using ``^``). The idea behind this is that
+there will be no breaking changes until version ``0.5.0``, so we can always
+be sure that our code will compile the way we intended it to. We do not fix
+the exact version of the compiler, so that bugfix releases are still possible.
+
+It is possible to specify much more complex rules for the compiler version,
+the expression follows those used by npm.
 
 .. index:: source file, ! import
 
diff --git a/libsolidity/analysis/SemVerHandler.cpp b/libsolidity/analysis/SemVerHandler.cpp
new file mode 100644
index 00000000..c7b212b2
--- /dev/null
+++ b/libsolidity/analysis/SemVerHandler.cpp
@@ -0,0 +1,290 @@
+/*
+	This file is part of cpp-ethereum.
+
+	cpp-ethereum is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	cpp-ethereum is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * @author Christian <chris@ethereum.org>
+ * @date 2016
+ * Utilities to handle semantic versioning.
+ */
+
+#include <libsolidity/analysis/SemVerHandler.h>
+#include <functional>
+
+using namespace std;
+using namespace dev;
+using namespace dev::solidity;
+
+SemVerVersion::SemVerVersion(string const& _versionString)
+{
+	auto i = _versionString.begin();
+	auto end = _versionString.end();
+
+	for (unsigned level = 0; level < 3; ++level)
+	{
+		unsigned v = 0;
+		for (; i != end && '0' <= *i && *i <= '9'; ++i)
+			v = v * 10 + (*i - '0');
+		numbers[level] = v;
+		if (level < 2)
+		{
+			if (i == end || *i != '.')
+				throw SemVerError();
+			else
+				++i;
+		}
+	}
+	if (i != end && *i == '-')
+	{
+		auto prereleaseStart = ++i;
+		while (i != end && *i != '+') ++i;
+		prerelease = string(prereleaseStart, i);
+	}
+	if (i != end && *i == '+')
+	{
+		auto buildStart = ++i;
+		while (i != end) ++i;
+		build = string(buildStart, i);
+	}
+	if (i != end)
+		throw SemVerError();
+}
+
+bool SemVerMatchExpression::MatchComponent::matches(SemVerVersion const& _version) const
+{
+	if (prefix == Token::BitNot)
+	{
+		MatchComponent comp = *this;
+
+		comp.prefix = Token::GreaterThanOrEqual;
+		if (!comp.matches(_version))
+			return false;
+
+		if (levelsPresent >= 2)
+			comp.levelsPresent = 2;
+		else
+			comp.levelsPresent = 1;
+		comp.prefix = Token::LessThanOrEqual;
+		return comp.matches(_version);
+	}
+	else if (prefix == Token::BitXor)
+	{
+		MatchComponent comp = *this;
+
+		comp.prefix = Token::GreaterThanOrEqual;
+		if (!comp.matches(_version))
+			return false;
+
+		if (comp.version.numbers[0] == 0)
+			comp.levelsPresent = 2;
+		else
+			comp.levelsPresent = 1;
+		comp.prefix = Token::LessThanOrEqual;
+		return comp.matches(_version);
+	}
+	else
+	{
+		int cmp = 0;
+		bool didCompare = false;
+		for (unsigned i = 0; i < levelsPresent && cmp == 0; i++)
+			if (version.numbers[i] != unsigned(-1))
+			{
+				didCompare = true;
+				cmp = _version.numbers[i] - version.numbers[i];
+			}
+		if (cmp == 0 && !_version.prerelease.empty() && didCompare)
+			cmp = -1;
+		if (prefix == Token::Assign)
+			return cmp == 0;
+		else if (prefix == Token::LessThan)
+			return cmp < 0;
+		else if (prefix == Token::LessThanOrEqual)
+			return cmp <= 0;
+		else if (prefix == Token::GreaterThan)
+			return cmp > 0;
+		else if (prefix == Token::GreaterThanOrEqual)
+			return cmp >= 0;
+		else
+			solAssert(false, "Invalid SemVer expression");
+		return false;
+	}
+}
+
+bool SemVerMatchExpression::Conjunction::matches(SemVerVersion const& _version) const
+{
+	for (auto const& component: components)
+		if (!component.matches(_version))
+			return false;
+	return true;
+}
+
+bool SemVerMatchExpression::matches(SemVerVersion const& _version) const
+{
+	if (!isValid())
+		return false;
+	for (auto const& range: m_disjunction)
+		if (range.matches(_version))
+			return true;
+	return false;
+}
+
+SemVerMatchExpression SemVerMatchExpressionParser::parse()
+{
+	reset();
+
+	try
+	{
+		while (true)
+		{
+			parseMatchExpression();
+			if (m_pos >= m_tokens.size())
+				break;
+			if (currentToken() != Token::Or)
+				throw SemVerError();
+			nextToken();
+		}
+	}
+	catch (SemVerError const&)
+	{
+		reset();
+	}
+
+	return m_expression;
+}
+
+
+void SemVerMatchExpressionParser::reset()
+{
+	m_expression = SemVerMatchExpression();
+	m_pos = 0;
+	m_posInside = 0;
+}
+
+void SemVerMatchExpressionParser::parseMatchExpression()
+{
+	// component - component (range)
+	// or component component* (conjunction)
+
+	SemVerMatchExpression::Conjunction range;
+	range.components.push_back(parseMatchComponent());
+	if (currentToken() == Token::Sub)
+	{
+		range.components[0].prefix = Token::GreaterThanOrEqual;
+		nextToken();
+		range.components.push_back(parseMatchComponent());
+		range.components[1].prefix = Token::LessThanOrEqual;
+	}
+	else
+		while (currentToken() != Token::Or && currentToken() != Token::Illegal)
+			range.components.push_back(parseMatchComponent());
+	m_expression.m_disjunction.push_back(range);
+}
+
+SemVerMatchExpression::MatchComponent SemVerMatchExpressionParser::parseMatchComponent()
+{
+	SemVerMatchExpression::MatchComponent component;
+	Token::Value token = currentToken();
+	if (
+		token == Token::BitXor ||
+		token == Token::BitNot ||
+		token == Token::LessThan ||
+		token == Token::LessThanOrEqual||
+		token == Token::GreaterThan ||
+		token == Token::GreaterThanOrEqual ||
+		token == Token::Assign
+	)
+	{
+		component.prefix = token;
+		nextToken();
+	}
+	else
+		component.prefix = Token::Assign;
+
+	component.levelsPresent = 0;
+	while (component.levelsPresent < 3)
+	{
+		component.version.numbers[component.levelsPresent] = parseVersionPart();
+		component.levelsPresent++;
+		if (currentChar() == '.')
+			nextChar();
+		else
+			break;
+	}
+	// TODO we do not support pre and build version qualifiers for now in match expressions
+	// (but we do support them in the actual versions)
+	return component;
+}
+
+unsigned SemVerMatchExpressionParser::parseVersionPart()
+{
+	auto startPos = m_pos;
+	char c = currentChar();
+	nextChar();
+	if (c == 'x' || c == 'X' || c == '*')
+		return unsigned(-1);
+	else if (c == '0')
+		return 0;
+	else if ('1' <= c && c <= '9')
+	{
+		unsigned v = c - '0';
+		// If we skip to the next token, the current number is terminated.
+		while (m_pos == startPos && '0' <= currentChar() && currentChar() <= '9')
+		{
+			c = currentChar();
+			if (v * 10 < v || v * 10 + (c - '0') < v * 10)
+				throw SemVerError();
+			v = v * 10 + c - '0';
+			nextChar();
+		}
+		return v;
+	}
+	else
+		throw SemVerError();
+}
+
+char SemVerMatchExpressionParser::currentChar() const
+{
+	if (m_pos >= m_literals.size())
+		return char(-1);
+	if (m_posInside >= m_literals[m_pos].size())
+		return char(-1);
+	return m_literals[m_pos][m_posInside];
+}
+
+char SemVerMatchExpressionParser::nextChar()
+{
+	if (m_pos < m_literals.size())
+	{
+		if (m_posInside + 1 >= m_literals[m_pos].size())
+			nextToken();
+		else
+			++m_posInside;
+	}
+	return currentChar();
+}
+
+Token::Value SemVerMatchExpressionParser::currentToken() const
+{
+	if (m_pos < m_tokens.size())
+		return m_tokens[m_pos];
+	else
+		return Token::Illegal;
+}
+
+void SemVerMatchExpressionParser::nextToken()
+{
+	++m_pos;
+	m_posInside = 0;
+}
diff --git a/libsolidity/analysis/SemVerHandler.h b/libsolidity/analysis/SemVerHandler.h
new file mode 100644
index 00000000..3c110b19
--- /dev/null
+++ b/libsolidity/analysis/SemVerHandler.h
@@ -0,0 +1,102 @@
+/*
+	This file is part of cpp-ethereum.
+
+	cpp-ethereum is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	cpp-ethereum is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * @author Christian <chris@ethereum.org>
+ * @date 2016
+ * Utilities to handle semantic versioning.
+ */
+
+#pragma once
+
+#include <vector>
+#include <libsolidity/parsing/Token.h>
+
+namespace dev
+{
+namespace solidity
+{
+
+class SemVerError: dev::Exception
+{
+};
+
+struct SemVerVersion
+{
+	unsigned numbers[3];
+	std::string prerelease;
+	std::string build;
+
+	explicit SemVerVersion(std::string const& _versionString = "0.0.0");
+};
+
+struct SemVerMatchExpression
+{
+	bool matches(SemVerVersion const& _version) const;
+
+	bool isValid() const { return !m_disjunction.empty(); }
+
+	struct MatchComponent
+	{
+		/// Prefix from < > <= >= ~ ^
+		Token::Value prefix = Token::Illegal;
+		/// Version, where unsigned(-1) in major, minor or patch denotes '*', 'x' or 'X'
+		SemVerVersion version;
+		/// Whether we have 1, 1.2 or 1.2.4
+		unsigned levelsPresent = 1;
+		bool matches(SemVerVersion const& _version) const;
+	};
+
+	struct Conjunction
+	{
+		std::vector<MatchComponent> components;
+		bool matches(SemVerVersion const& _version) const;
+	};
+
+	std::vector<Conjunction> m_disjunction;
+};
+
+class SemVerMatchExpressionParser
+{
+public:
+	SemVerMatchExpressionParser(std::vector<Token::Value> const& _tokens, std::vector<std::string> const& _literals):
+		m_tokens(_tokens), m_literals(_literals)
+	{}
+	SemVerMatchExpression parse();
+
+private:
+	void reset();
+
+	void parseMatchExpression();
+	SemVerMatchExpression::MatchComponent parseMatchComponent();
+	unsigned parseVersionPart();
+
+	char currentChar() const;
+	char nextChar();
+	Token::Value currentToken() const;
+	void nextToken();
+
+	std::vector<Token::Value> m_tokens;
+	std::vector<std::string> m_literals;
+
+	unsigned m_pos = 0;
+	unsigned m_posInside = 0;
+
+	SemVerMatchExpression m_expression;
+};
+
+}
+}
diff --git a/libsolidity/analysis/SyntaxChecker.cpp b/libsolidity/analysis/SyntaxChecker.cpp
index 593f2f69..a95b4879 100644
--- a/libsolidity/analysis/SyntaxChecker.cpp
+++ b/libsolidity/analysis/SyntaxChecker.cpp
@@ -15,9 +15,11 @@
 	along with cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
 */
 
+#include <libsolidity/analysis/SyntaxChecker.h>
 #include <memory>
 #include <libsolidity/ast/AST.h>
-#include <libsolidity/analysis/SyntaxChecker.h>
+#include <libsolidity/analysis/SemVerHandler.h>
+#include <libsolidity/interface/Version.h>
 
 using namespace std;
 using namespace dev;
@@ -27,7 +29,7 @@ using namespace dev::solidity;
 bool SyntaxChecker::checkSyntax(SourceUnit const& _sourceUnit)
 {
 	_sourceUnit.accept(*this);
-	return m_errors.empty();
+	return Error::containsOnlyWarnings(m_errors);
 }
 
 void SyntaxChecker::syntaxError(SourceLocation const& _location, std::string const& _description)
@@ -40,6 +42,52 @@ void SyntaxChecker::syntaxError(SourceLocation const& _location, std::string con
 	m_errors.push_back(err);
 }
 
+bool SyntaxChecker::visit(SourceUnit const&)
+{
+	m_versionPragmaFound = false;
+	return true;
+}
+
+void SyntaxChecker::endVisit(SourceUnit const& _sourceUnit)
+{
+	if (!m_versionPragmaFound)
+	{
+		auto err = make_shared<Error>(Error::Type::Warning);
+		*err <<
+			errinfo_sourceLocation(_sourceUnit.location()) <<
+			errinfo_comment(
+				string("Source file does not specify required compiler version! ") +
+				string("Consider adding \"pragma solidity ^") + VersionNumber + string(";\".")
+			);
+		m_errors.push_back(err);
+	}
+}
+
+bool SyntaxChecker::visit(PragmaDirective const& _pragma)
+{
+	solAssert(!_pragma.tokens().empty(), "");
+	solAssert(_pragma.tokens().size() == _pragma.literals().size(), "");
+	if (_pragma.tokens()[0] != Token::Identifier && _pragma.literals()[0] != "solidity")
+		syntaxError(_pragma.location(), "Unknown pragma \"" + _pragma.literals()[0] + "\"");
+	else
+	{
+		vector<Token::Value> tokens(_pragma.tokens().begin() + 1, _pragma.tokens().end());
+		vector<string> literals(_pragma.literals().begin() + 1, _pragma.literals().end());
+		SemVerMatchExpressionParser parser(tokens, literals);
+		auto matchExpression = parser.parse();
+		SemVerVersion currentVersion{string(VersionString)};
+		if (!matchExpression.matches(currentVersion))
+			syntaxError(
+				_pragma.location(),
+				"Source file requires different compiler version (current compiler is " +
+				string(VersionString) + " - note that nightly builds are considered to be "
+				"strictly less than the released version"
+			);
+		m_versionPragmaFound = true;
+	}
+	return true;
+}
+
 bool SyntaxChecker::visit(ModifierDefinition const&)
 {
 	m_placeholderFound = false;
@@ -91,7 +139,7 @@ bool SyntaxChecker::visit(Break const& _breakStatement)
 	return true;
 }
 
-bool SyntaxChecker::visit(const PlaceholderStatement&)
+bool SyntaxChecker::visit(PlaceholderStatement const&)
 {
 	m_placeholderFound = true;
 	return true;
diff --git a/libsolidity/analysis/SyntaxChecker.h b/libsolidity/analysis/SyntaxChecker.h
index 3198ffd0..ac8ed872 100644
--- a/libsolidity/analysis/SyntaxChecker.h
+++ b/libsolidity/analysis/SyntaxChecker.h
@@ -45,6 +45,10 @@ private:
 	/// Adds a new error to the list of errors.
 	void syntaxError(SourceLocation const& _location, std::string const& _description);
 
+	virtual bool visit(SourceUnit const& _sourceUnit) override;
+	virtual void endVisit(SourceUnit const& _sourceUnit) override;
+	virtual bool visit(PragmaDirective const& _pragma) override;
+
 	virtual bool visit(ModifierDefinition const& _modifier) override;
 	virtual void endVisit(ModifierDefinition const& _modifier) override;
 
@@ -63,6 +67,9 @@ private:
 	/// Flag that indicates whether a function modifier actually contains '_'.
 	bool m_placeholderFound = false;
 
+	/// Flag that indicates whether some version pragma was present.
+	bool m_versionPragmaFound = false;
+
 	int m_inLoopDepth = 0;
 };
 
diff --git a/libsolidity/ast/AST.h b/libsolidity/ast/AST.h
index bf275869..761d85fe 100644
--- a/libsolidity/ast/AST.h
+++ b/libsolidity/ast/AST.h
@@ -176,6 +176,34 @@ private:
 };
 
 /**
+ * Pragma directive, only version requirements in the form `pragma solidity "^0.4.0";` are
+ * supported for now.
+ */
+class PragmaDirective: public ASTNode
+{
+public:
+	PragmaDirective(
+		SourceLocation const& _location,
+		std::vector<Token::Value> const& _tokens,
+		std::vector<ASTString> const& _literals
+	): ASTNode(_location), m_tokens(_tokens), m_literals(_literals)
+	{}
+
+	virtual void accept(ASTVisitor& _visitor) override;
+	virtual void accept(ASTConstVisitor& _visitor) const override;
+
+	std::vector<Token::Value> const& tokens() const { return m_tokens; }
+	std::vector<ASTString> const& literals() const { return m_literals; }
+
+private:
+
+	/// Sequence of tokens following the "pragma" keyword.
+	std::vector<Token::Value> m_tokens;
+	/// Sequence of literals following the "pragma" keyword.
+	std::vector<ASTString> m_literals;
+};
+
+/**
  * Import directive for referencing other files / source objects.
  * Example: import "abc.sol" // imports all symbols of "abc.sol" into current scope
  * Source objects are identified by a string which can be a file name but does not have to be.
diff --git a/libsolidity/ast/ASTForward.h b/libsolidity/ast/ASTForward.h
index dad2b2e2..59fc1b57 100644
--- a/libsolidity/ast/ASTForward.h
+++ b/libsolidity/ast/ASTForward.h
@@ -35,6 +35,7 @@ namespace solidity
 
 class ASTNode;
 class SourceUnit;
+class PragmaDirective;
 class ImportDirective;
 class Declaration;
 class ContractDefinition;
diff --git a/libsolidity/ast/ASTJsonConverter.cpp b/libsolidity/ast/ASTJsonConverter.cpp
index 35fd0b7d..49ee6d34 100644
--- a/libsolidity/ast/ASTJsonConverter.cpp
+++ b/libsolidity/ast/ASTJsonConverter.cpp
@@ -103,6 +103,15 @@ bool ASTJsonConverter::visit(SourceUnit const&)
 	return true;
 }
 
+bool ASTJsonConverter::visit(PragmaDirective const& _node)
+{
+	Json::Value literals(Json::arrayValue);
+	for (auto const& literal: _node.literals())
+		literals.append(literal);
+	addJsonNode(_node, "PragmaDirective", { make_pair("literals", literals) });
+	return true;
+}
+
 bool ASTJsonConverter::visit(ImportDirective const& _node)
 {
 	addJsonNode(_node, "ImportDirective", { make_pair("file", _node.path())});
@@ -401,6 +410,10 @@ void ASTJsonConverter::endVisit(SourceUnit const&)
 	goUp();
 }
 
+void ASTJsonConverter::endVisit(PragmaDirective const&)
+{
+}
+
 void ASTJsonConverter::endVisit(ImportDirective const&)
 {
 }
diff --git a/libsolidity/ast/ASTJsonConverter.h b/libsolidity/ast/ASTJsonConverter.h
index 97aa8654..7c7b37f8 100644
--- a/libsolidity/ast/ASTJsonConverter.h
+++ b/libsolidity/ast/ASTJsonConverter.h
@@ -52,6 +52,7 @@ public:
 	Json::Value const& json();
 
 	bool visit(SourceUnit const& _node) override;
+	bool visit(PragmaDirective const& _node) override;
 	bool visit(ImportDirective const& _node) override;
 	bool visit(ContractDefinition const& _node) override;
 	bool visit(InheritanceSpecifier const& _node) override;
@@ -96,6 +97,7 @@ public:
 	bool visit(Literal const& _node) override;
 
 	void endVisit(SourceUnit const&) override;
+	void endVisit(PragmaDirective const&) override;
 	void endVisit(ImportDirective const&) override;
 	void endVisit(ContractDefinition const&) override;
 	void endVisit(InheritanceSpecifier const&) override;
diff --git a/libsolidity/ast/ASTPrinter.cpp b/libsolidity/ast/ASTPrinter.cpp
index 9ed9c6d5..a9de457a 100644
--- a/libsolidity/ast/ASTPrinter.cpp
+++ b/libsolidity/ast/ASTPrinter.cpp
@@ -47,6 +47,13 @@ void ASTPrinter::print(ostream& _stream)
 }
 
 
+bool ASTPrinter::visit(PragmaDirective const& _node)
+{
+	writeLine("PragmaDirective");
+	printSourcePart(_node);
+	return goDeeper();
+}
+
 bool ASTPrinter::visit(ImportDirective const& _node)
 {
 	writeLine("ImportDirective \"" + _node.path() + "\"");
@@ -355,6 +362,11 @@ bool ASTPrinter::visit(Literal const& _node)
 	return goDeeper();
 }
 
+void ASTPrinter::endVisit(PragmaDirective const&)
+{
+	m_indentation--;
+}
+
 void ASTPrinter::endVisit(ImportDirective const&)
 {
 	m_indentation--;
diff --git a/libsolidity/ast/ASTPrinter.h b/libsolidity/ast/ASTPrinter.h
index a2546935..f0ab1098 100644
--- a/libsolidity/ast/ASTPrinter.h
+++ b/libsolidity/ast/ASTPrinter.h
@@ -47,6 +47,7 @@ public:
 	/// Output the string representation of the AST to _stream.
 	void print(std::ostream& _stream);
 
+	bool visit(PragmaDirective const& _node) override;
 	bool visit(ImportDirective const& _node) override;
 	bool visit(ContractDefinition const& _node) override;
 	bool visit(InheritanceSpecifier const& _node) override;
@@ -89,6 +90,7 @@ public:
 	bool visit(ElementaryTypeNameExpression const& _node) override;
 	bool visit(Literal const& _node) override;
 
+	void endVisit(PragmaDirective const&) override;
 	void endVisit(ImportDirective const&) override;
 	void endVisit(ContractDefinition const&) override;
 	void endVisit(InheritanceSpecifier const&) override;
diff --git a/libsolidity/ast/ASTVisitor.h b/libsolidity/ast/ASTVisitor.h
index 5aac2066..3a1b55d3 100644
--- a/libsolidity/ast/ASTVisitor.h
+++ b/libsolidity/ast/ASTVisitor.h
@@ -44,6 +44,7 @@ class ASTVisitor
 {
 public:
 	virtual bool visit(SourceUnit& _node) { return visitNode(_node); }
+	virtual bool visit(PragmaDirective& _node) { return visitNode(_node); }
 	virtual bool visit(ImportDirective& _node) { return visitNode(_node); }
 	virtual bool visit(ContractDefinition& _node) { return visitNode(_node); }
 	virtual bool visit(InheritanceSpecifier& _node) { return visitNode(_node); }
@@ -88,6 +89,7 @@ public:
 	virtual bool visit(Literal& _node) { return visitNode(_node); }
 
 	virtual void endVisit(SourceUnit& _node) { endVisitNode(_node); }
+	virtual void endVisit(PragmaDirective& _node) { endVisitNode(_node); }
 	virtual void endVisit(ImportDirective& _node) { endVisitNode(_node); }
 	virtual void endVisit(ContractDefinition& _node) { endVisitNode(_node); }
 	virtual void endVisit(InheritanceSpecifier& _node) { endVisitNode(_node); }
@@ -144,6 +146,7 @@ class ASTConstVisitor
 {
 public:
 	virtual bool visit(SourceUnit const& _node) { return visitNode(_node); }
+	virtual bool visit(PragmaDirective const& _node) { return visitNode(_node); }
 	virtual bool visit(ImportDirective const& _node) { return visitNode(_node); }
 	virtual bool visit(ContractDefinition const& _node) { return visitNode(_node); }
 	virtual bool visit(InheritanceSpecifier const& _node) { return visitNode(_node); }
@@ -188,6 +191,7 @@ public:
 	virtual bool visit(Literal const& _node) { return visitNode(_node); }
 
 	virtual void endVisit(SourceUnit const& _node) { endVisitNode(_node); }
+	virtual void endVisit(PragmaDirective const& _node) { endVisitNode(_node); }
 	virtual void endVisit(ImportDirective const& _node) { endVisitNode(_node); }
 	virtual void endVisit(ContractDefinition const& _node) { endVisitNode(_node); }
 	virtual void endVisit(InheritanceSpecifier const& _node) { endVisitNode(_node); }
diff --git a/libsolidity/ast/AST_accept.h b/libsolidity/ast/AST_accept.h
index dd2a7d60..b5a3806b 100644
--- a/libsolidity/ast/AST_accept.h
+++ b/libsolidity/ast/AST_accept.h
@@ -45,6 +45,18 @@ void SourceUnit::accept(ASTConstVisitor& _visitor) const
 	_visitor.endVisit(*this);
 }
 
+void PragmaDirective::accept(ASTVisitor& _visitor)
+{
+	_visitor.visit(*this);
+	_visitor.endVisit(*this);
+}
+
+void PragmaDirective::accept(ASTConstVisitor& _visitor) const
+{
+	_visitor.visit(*this);
+	_visitor.endVisit(*this);
+}
+
 void ImportDirective::accept(ASTVisitor& _visitor)
 {
 	_visitor.visit(*this);
diff --git a/libsolidity/grammar.txt b/libsolidity/grammar.txt
index 0d1f68a6..0230729a 100644
--- a/libsolidity/grammar.txt
+++ b/libsolidity/grammar.txt
@@ -1,13 +1,16 @@
-SourceUnit = (ImportDirective | ContractDefinition)*
+SourceUnit = (PragmaDirective | ImportDirective | ContractDefinition)*
 
-ContractDefinition = ( 'contract' | 'library' ) Identifier
-                     ( 'is' InheritanceSpecifier (',' InheritanceSpecifier )* )?
-                     '{' ContractPart* '}'
+// Pragma actually parses anything up to the trailing ';' to be fully forward-compatible.
+PragmaDirective = 'pragma' Identifier Expression ';'
 
 ImportDirective = 'import' StringLiteral ('as' Identifier)? ';'
         | 'import' ('*' | Identifier) ('as' Identifier)? 'from' StringLiteral ';'
         | 'import' '{' Identifier ('as' Identifier)? ( ',' Identifier ('as' Identifier)? )* '}' 'from' StringLiteral ';'
 
+ContractDefinition = ( 'contract' | 'library' ) Identifier
+                     ( 'is' InheritanceSpecifier (',' InheritanceSpecifier )* )?
+                     '{' ContractPart* '}'
+
 ContractPart = StateVariableDeclaration | UsingForDeclaration
              | StructDefinition | ModifierDefinition | FunctionDefinition | EventDefinition | EnumDefinition
 
diff --git a/libsolidity/parsing/Parser.cpp b/libsolidity/parsing/Parser.cpp
index b8f72238..b2f4a156 100644
--- a/libsolidity/parsing/Parser.cpp
+++ b/libsolidity/parsing/Parser.cpp
@@ -76,6 +76,9 @@ ASTPointer<SourceUnit> Parser::parse(shared_ptr<Scanner> const& _scanner)
 		{
 			switch (auto token = m_scanner->currentToken())
 			{
+			case Token::Pragma:
+				nodes.push_back(parsePragmaDirective());
+				break;
 			case Token::Import:
 				nodes.push_back(parseImportDirective());
 				break;
@@ -97,6 +100,36 @@ ASTPointer<SourceUnit> Parser::parse(shared_ptr<Scanner> const& _scanner)
 	}
 }
 
+ASTPointer<PragmaDirective> Parser::parsePragmaDirective()
+{
+	// pragma anything* ;
+	// Currently supported:
+	// pragma solidity ^0.4.0 || ^0.3.0;
+	ASTNodeFactory nodeFactory(*this);
+	expectToken(Token::Pragma);
+	vector<string> literals;
+	vector<Token::Value> tokens;
+	do
+	{
+		Token::Value token = m_scanner->currentToken();
+		if (token == Token::Illegal)
+			parserError("Token incompatible with Solidity parser as part of pragma directive.");
+		else
+		{
+			string literal = m_scanner->currentLiteral();
+			if (literal.empty() && Token::toString(token))
+				literal = Token::toString(token);
+			literals.push_back(literal);
+			tokens.push_back(token);
+		}
+		m_scanner->next();
+	}
+	while (m_scanner->currentToken() != Token::Semicolon && m_scanner->currentToken() != Token::EOS);
+	nodeFactory.markEndPosition();
+	expectToken(Token::Semicolon);
+	return nodeFactory.createNode<PragmaDirective>(tokens, literals);
+}
+
 ASTPointer<ImportDirective> Parser::parseImportDirective()
 {
 	// import "abc" [as x];
diff --git a/libsolidity/parsing/Parser.h b/libsolidity/parsing/Parser.h
index d776c3fd..9c30cf60 100644
--- a/libsolidity/parsing/Parser.h
+++ b/libsolidity/parsing/Parser.h
@@ -55,6 +55,7 @@ private:
 
 	///@{
 	///@name Parsing functions for the AST nodes
+	ASTPointer<PragmaDirective> parsePragmaDirective();
 	ASTPointer<ImportDirective> parseImportDirective();
 	ASTPointer<ContractDefinition> parseContractDefinition(bool _isLibrary);
 	ASTPointer<InheritanceSpecifier> parseInheritanceSpecifier();
diff --git a/libsolidity/parsing/Token.h b/libsolidity/parsing/Token.h
index 007baef4..15d4860f 100644
--- a/libsolidity/parsing/Token.h
+++ b/libsolidity/parsing/Token.h
@@ -167,6 +167,7 @@ namespace solidity
 	K(Modifier, "modifier", 0)                                         \
 	K(New, "new", 0)                                                   \
 	K(Public, "public", 0)                                             \
+	K(Pragma, "pragma", 0)                                             \
 	K(Private, "private", 0)                                           \
 	K(Return, "return", 0)                                             \
 	K(Returns, "returns", 0)                                           \
diff --git a/test/contracts/AuctionRegistrar.cpp b/test/contracts/AuctionRegistrar.cpp
index 6eba2706..681caa26 100644
--- a/test/contracts/AuctionRegistrar.cpp
+++ b/test/contracts/AuctionRegistrar.cpp
@@ -39,7 +39,7 @@ namespace
 {
 
 static char const* registrarCode = R"DELIMITER(
-//sol
+pragma solidity ^0.3.5;
 
 contract NameRegister {
 	function addr(string _name) constant returns (address o_owner);
diff --git a/test/contracts/FixedFeeRegistrar.cpp b/test/contracts/FixedFeeRegistrar.cpp
index 3acfba62..fd0861f7 100644
--- a/test/contracts/FixedFeeRegistrar.cpp
+++ b/test/contracts/FixedFeeRegistrar.cpp
@@ -52,6 +52,8 @@ static char const* registrarCode = R"DELIMITER(
 // @authors:
 //   Gav Wood <g@ethdev.com>
 
+pragma solidity ^0.3.5;
+
 contract Registrar {
 	event Changed(string indexed name);
 
diff --git a/test/contracts/Wallet.cpp b/test/contracts/Wallet.cpp
index 9e797af4..55c2e1af 100644
--- a/test/contracts/Wallet.cpp
+++ b/test/contracts/Wallet.cpp
@@ -54,6 +54,9 @@ static char const* walletCode = R"DELIMITER(
 // use modifiers onlyowner (just own owned) or onlymanyowners(hash), whereby the same hash must be provided by
 // some number (specified in constructor) of the set of owners (specified in the constructor, modifiable) before the
 // interior is executed.
+
+pragma solidity ^0.3.5;
+
 contract multiowned {
 
 	// TYPES
diff --git a/test/libsolidity/GasMeter.cpp b/test/libsolidity/GasMeter.cpp
index 41204a0a..1f216680 100644
--- a/test/libsolidity/GasMeter.cpp
+++ b/test/libsolidity/GasMeter.cpp
@@ -46,7 +46,7 @@ public:
 	GasMeterTestFramework() { }
 	void compile(string const& _sourceCode)
 	{
-		m_compiler.setSource(_sourceCode);
+		m_compiler.setSource("pragma solidity >= 0.0;" + _sourceCode);
 		ETH_TEST_REQUIRE_NO_THROW(m_compiler.compile(), "Compiling contract failed");
 
 		AssemblyItems const* items = m_compiler.runtimeAssemblyItems("");
diff --git a/test/libsolidity/Imports.cpp b/test/libsolidity/Imports.cpp
index 0736a853..1a9e16cc 100644
--- a/test/libsolidity/Imports.cpp
+++ b/test/libsolidity/Imports.cpp
@@ -39,106 +39,106 @@ BOOST_AUTO_TEST_SUITE(SolidityImports)
 BOOST_AUTO_TEST_CASE(smoke_test)
 {
 	CompilerStack c;
-	c.addSource("a", "contract C {}");
+	c.addSource("a", "contract C {} pragma solidity >=0.0;");
 	BOOST_CHECK(c.compile());
 }
 
 BOOST_AUTO_TEST_CASE(regular_import)
 {
 	CompilerStack c;
-	c.addSource("a", "contract C {}");
-	c.addSource("b", "import \"a\"; contract D is C {}");
+	c.addSource("a", "contract C {} pragma solidity >=0.0;");
+	c.addSource("b", "import \"a\"; contract D is C {} pragma solidity >=0.0;");
 	BOOST_CHECK(c.compile());
 }
 
 BOOST_AUTO_TEST_CASE(import_does_not_clutter_importee)
 {
 	CompilerStack c;
-	c.addSource("a", "contract C { D d; }");
-	c.addSource("b", "import \"a\"; contract D is C {}");
+	c.addSource("a", "contract C { D d; } pragma solidity >=0.0;");
+	c.addSource("b", "import \"a\"; contract D is C {} pragma solidity >=0.0;");
 	BOOST_CHECK(!c.compile());
 }
 
 BOOST_AUTO_TEST_CASE(import_is_transitive)
 {
 	CompilerStack c;
-	c.addSource("a", "contract C { }");
-	c.addSource("b", "import \"a\";");
-	c.addSource("c", "import \"b\"; contract D is C {}");
+	c.addSource("a", "contract C { } pragma solidity >=0.0;");
+	c.addSource("b", "import \"a\"; pragma solidity >=0.0;");
+	c.addSource("c", "import \"b\"; contract D is C {} pragma solidity >=0.0;");
 	BOOST_CHECK(c.compile());
 }
 
 BOOST_AUTO_TEST_CASE(circular_import)
 {
 	CompilerStack c;
-	c.addSource("a", "import \"b\"; contract C { D d; }");
-	c.addSource("b", "import \"a\"; contract D { C c; }");
+	c.addSource("a", "import \"b\"; contract C { D d; } pragma solidity >=0.0;");
+	c.addSource("b", "import \"a\"; contract D { C c; } pragma solidity >=0.0;");
 	BOOST_CHECK(c.compile());
 }
 
 BOOST_AUTO_TEST_CASE(relative_import)
 {
 	CompilerStack c;
-	c.addSource("a", "import \"./dir/b\"; contract A is B {}");
-	c.addSource("dir/b", "contract B {}");
-	c.addSource("dir/c", "import \"../a\"; contract C is A {}");
+	c.addSource("a", "import \"./dir/b\"; contract A is B {} pragma solidity >=0.0;");
+	c.addSource("dir/b", "contract B {} pragma solidity >=0.0;");
+	c.addSource("dir/c", "import \"../a\"; contract C is A {} pragma solidity >=0.0;");
 	BOOST_CHECK(c.compile());
 }
 
 BOOST_AUTO_TEST_CASE(relative_import_multiplex)
 {
 	CompilerStack c;
-	c.addSource("a", "contract A {}");
-	c.addSource("dir/a/b/c", "import \"../../.././a\"; contract B is A {}");
+	c.addSource("a", "contract A {} pragma solidity >=0.0;");
+	c.addSource("dir/a/b/c", "import \"../../.././a\"; contract B is A {} pragma solidity >=0.0;");
 	BOOST_CHECK(c.compile());
 }
 
 BOOST_AUTO_TEST_CASE(simple_alias)
 {
 	CompilerStack c;
-	c.addSource("a", "contract A {}");
-	c.addSource("dir/a/b/c", "import \"../../.././a\" as x; contract B is x.A { function() { x.A r = x.A(20); } }");
+	c.addSource("a", "contract A {} pragma solidity >=0.0;");
+	c.addSource("dir/a/b/c", "import \"../../.././a\" as x; contract B is x.A { function() { x.A r = x.A(20); } } pragma solidity >=0.0;");
 	BOOST_CHECK(c.compile());
 }
 
 BOOST_AUTO_TEST_CASE(library_name_clash)
 {
 	CompilerStack c;
-	c.addSource("a", "library A {}");
-	c.addSource("b", "library A {}");
+	c.addSource("a", "library A {} pragma solidity >=0.0;");
+	c.addSource("b", "library A {} pragma solidity >=0.0;");
 	BOOST_CHECK(!c.compile());
 }
 
 BOOST_AUTO_TEST_CASE(library_name_clash_with_contract)
 {
 	CompilerStack c;
-	c.addSource("a", "contract A {}");
-	c.addSource("b", "library A {}");
+	c.addSource("a", "contract A {} pragma solidity >=0.0;");
+	c.addSource("b", "library A {} pragma solidity >=0.0;");
 	BOOST_CHECK(c.compile());
 }
 
 BOOST_AUTO_TEST_CASE(complex_import)
 {
 	CompilerStack c;
-	c.addSource("a", "contract A {} contract B {} contract C { struct S { uint a; } }");
+	c.addSource("a", "contract A {} contract B {} contract C { struct S { uint a; } } pragma solidity >=0.0;");
 	c.addSource("b", "import \"a\" as x; import {B as b, C as c, C} from \"a\"; "
-				"contract D is b { function f(c.S var1, x.C.S var2, C.S var3) internal {} }");
+				"contract D is b { function f(c.S var1, x.C.S var2, C.S var3) internal {} } pragma solidity >=0.0;");
 	BOOST_CHECK(c.compile());
 }
 
 BOOST_AUTO_TEST_CASE(name_clash_in_import)
 {
 	CompilerStack c;
-	c.addSource("a", "contract A {}");
-	c.addSource("b", "import \"a\"; contract A {} ");
+	c.addSource("a", "contract A {} pragma solidity >=0.0;");
+	c.addSource("b", "import \"a\"; contract A {} pragma solidity >=0.0;");
 	BOOST_CHECK(!c.compile());
-	c.addSource("b", "import \"a\" as A; contract A {} ");
+	c.addSource("b", "import \"a\" as A; contract A {} pragma solidity >=0.0;");
 	BOOST_CHECK(!c.compile());
-	c.addSource("b", "import {A as b} from \"a\"; contract b {} ");
+	c.addSource("b", "import {A as b} from \"a\"; contract b {} pragma solidity >=0.0;");
 	BOOST_CHECK(!c.compile());
-	c.addSource("b", "import {A} from \"a\"; contract A {} ");
+	c.addSource("b", "import {A} from \"a\"; contract A {} pragma solidity >=0.0;");
 	BOOST_CHECK(!c.compile());
-	c.addSource("b", "import {A} from \"a\"; contract B {} ");
+	c.addSource("b", "import {A} from \"a\"; contract B {} pragma solidity >=0.0;");
 	BOOST_CHECK(c.compile());
 }
 
@@ -146,10 +146,10 @@ BOOST_AUTO_TEST_CASE(remappings)
 {
 	CompilerStack c;
 	c.setRemappings(vector<string>{"s=s_1.4.6", "t=Tee"});
-	c.addSource("a", "import \"s/s.sol\"; contract A is S {}");
-	c.addSource("b", "import \"t/tee.sol\"; contract A is Tee {} ");
-	c.addSource("s_1.4.6/s.sol", "contract S {}");
-	c.addSource("Tee/tee.sol", "contract Tee {}");
+	c.addSource("a", "import \"s/s.sol\"; contract A is S {} pragma solidity >=0.0;");
+	c.addSource("b", "import \"t/tee.sol\"; contract A is Tee {} pragma solidity >=0.0;");
+	c.addSource("s_1.4.6/s.sol", "contract S {} pragma solidity >=0.0;");
+	c.addSource("Tee/tee.sol", "contract Tee {} pragma solidity >=0.0;");
 	BOOST_CHECK(c.compile());
 }
 
@@ -157,10 +157,10 @@ BOOST_AUTO_TEST_CASE(context_dependent_remappings)
 {
 	CompilerStack c;
 	c.setRemappings(vector<string>{"a:s=s_1.4.6", "b:s=s_1.4.7"});
-	c.addSource("a/a.sol", "import \"s/s.sol\"; contract A is SSix {}");
-	c.addSource("b/b.sol", "import \"s/s.sol\"; contract B is SSeven {}");
-	c.addSource("s_1.4.6/s.sol", "contract SSix {} ");
-	c.addSource("s_1.4.7/s.sol", "contract SSeven {} ");
+	c.addSource("a/a.sol", "import \"s/s.sol\"; contract A is SSix {} pragma solidity >=0.0;");
+	c.addSource("b/b.sol", "import \"s/s.sol\"; contract B is SSeven {} pragma solidity >=0.0;");
+	c.addSource("s_1.4.6/s.sol", "contract SSix {} pragma solidity >=0.0;");
+	c.addSource("s_1.4.7/s.sol", "contract SSeven {} pragma solidity >=0.0;");
 	BOOST_CHECK(c.compile());
 }
 
diff --git a/test/libsolidity/SemVerMatcher.cpp b/test/libsolidity/SemVerMatcher.cpp
new file mode 100644
index 00000000..80bdf16f
--- /dev/null
+++ b/test/libsolidity/SemVerMatcher.cpp
@@ -0,0 +1,223 @@
+/*
+	This file is part of cpp-ethereum.
+
+	cpp-ethereum is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	cpp-ethereum is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * @author Christian <chris@ethereum.org>
+ * @date 2016
+ * Unit tests for the semantic versioning matcher.
+ */
+
+#include <string>
+#include <vector>
+#include <tuple>
+#include <libsolidity/parsing/Scanner.h>
+#include <libsolidity/analysis/SemVerHandler.h>
+#include "../TestHelper.h"
+
+using namespace std;
+
+namespace dev
+{
+namespace solidity
+{
+namespace test
+{
+
+BOOST_AUTO_TEST_SUITE(SemVerMatcher)
+
+SemVerMatchExpression parseExpression(string const& _input)
+{
+	Scanner scanner{CharStream(_input)};
+	vector<string> literals;
+	vector<Token::Value> tokens;
+	while (scanner.currentToken() != Token::EOS)
+	{
+		auto token = scanner.currentToken();
+		string literal = scanner.currentLiteral();
+		if (literal.empty() && Token::toString(token))
+			literal = Token::toString(token);
+		literals.push_back(literal);
+		tokens.push_back(token);
+		scanner.next();
+	}
+
+	auto expression = SemVerMatchExpressionParser(tokens, literals).parse();
+	BOOST_CHECK_MESSAGE(
+		expression.isValid(),
+		"Expression \"" + _input + "\" did not parse properly."
+	);
+	return expression;
+}
+
+BOOST_AUTO_TEST_CASE(positive_range)
+{
+	// Positive range tests
+	vector<pair<string, string>> tests = {
+		{"*", "1.2.3-foo"},
+		{"1.0.0 - 2.0.0", "1.2.3"},
+		{"1.0.0", "1.0.0"},
+		{">=*", "0.2.4"},
+		{"*", "1.2.3"},
+		{">=1.0.0", "1.0.0"},
+		{">=1.0.0", "1.0.1"},
+		{">=1.0.0", "1.1.0"},
+		{">1.0.0", "1.0.1"},
+		{">1.0.0", "1.1.0"},
+		{"<=2.0.0", "2.0.0"},
+		{"<=2.0.0", "1.9999.9999"},
+		{"<=2.0.0", "0.2.9"},
+		{"<2.0.0", "1.9999.9999"},
+		{"<2.0.0", "0.2.9"},
+		{">= 1.0.0", "1.0.0"},
+		{">=  1.0.0", "1.0.1"},
+		{">=   1.0.0", "1.1.0"},
+		{"> 1.0.0", "1.0.1"},
+		{">  1.0.0", "1.1.0"},
+		{"<=   2.0.0", "2.0.0"},
+		{"<= 2.0.0", "1.9999.9999"},
+		{"<=  2.0.0", "0.2.9"},
+		{"<    2.0.0", "1.9999.9999"},
+		{"<\t2.0.0", "0.2.9"},
+		{">=0.1.97", "0.1.97"},
+		{"0.1.20 || 1.2.4", "1.2.4"},
+		{">=0.2.3 || <0.0.1", "0.0.0"},
+		{">=0.2.3 || <0.0.1", "0.2.3"},
+		{">=0.2.3 || <0.0.1", "0.2.4"},
+		{"\"2.x.x\"", "2.1.3"},
+		{"1.2.x", "1.2.3"},
+		{"\"1.2.x\" || \"2.x\"", "2.1.3"},
+		{"\"1.2.x\" || \"2.x\"", "1.2.3"},
+		{"x", "1.2.3"},
+		{"2.*.*", "2.1.3"},
+		{"1.2.*", "1.2.3"},
+		{"1.2.* || 2.*", "2.1.3"},
+		{"1.2.* || 2.*", "1.2.3"},
+		{"*", "1.2.3"},
+		{"2", "2.1.2"},
+		{"2.3", "2.3.1"},
+		{"~2.4", "2.4.0"}, // >=2.4.0 <2.5.0
+		{"~2.4", "2.4.5"},
+		{"~1", "1.2.3"}, // >=1.0.0 <2.0.0
+		{"~1.0", "1.0.2"}, // >=1.0.0 <1.1.0,
+		{"~ 1.0", "1.0.2"},
+		{"~ 1.0.3", "1.0.12"},
+		{">=1", "1.0.0"},
+		{">= 1", "1.0.0"},
+		{"<1.2", "1.1.1"},
+		{"< 1.2", "1.1.1"},
+		{"=0.7.x", "0.7.2"},
+		{"<=0.7.x", "0.7.2"},
+		{">=0.7.x", "0.7.2"},
+		{"<=0.7.x", "0.6.2"},
+		{"~1.2.1 >=1.2.3", "1.2.3"},
+		{"~1.2.1 =1.2.3", "1.2.3"},
+		{"~1.2.1 1.2.3", "1.2.3"},
+		{"~1.2.1 >=1.2.3 1.2.3", "1.2.3"},
+		{"~1.2.1 1.2.3 >=1.2.3", "1.2.3"},
+		{">=\"1.2.1\" 1.2.3", "1.2.3"},
+		{"1.2.3 >=1.2.1", "1.2.3"},
+		{">=1.2.3 >=1.2.1", "1.2.3"},
+		{">=1.2.1 >=1.2.3", "1.2.3"},
+		{">=1.2", "1.2.8"},
+		{"^1.2.3", "1.8.1"},
+		{"^0.1.2", "0.1.2"},
+		{"^0.1", "0.1.2"},
+		{"^1.2", "1.4.2"},
+		{"<=1.2.3", "1.2.3-beta"},
+		{">1.2", "1.3.0-beta"},
+		{"<1.2.3", "1.2.3-beta"},
+		{"^1.2 ^1", "1.4.2"}
+	};
+	for (auto const& t: tests)
+	{
+		SemVerVersion version(t.second);
+		SemVerMatchExpression expression = parseExpression(t.first);
+		BOOST_CHECK_MESSAGE(
+			expression.matches(version),
+			"Version \"" + t.second + "\" did not satisfy expression \"" + t.first + "\""
+		);
+	}
+}
+
+BOOST_AUTO_TEST_CASE(negative_range)
+{
+	// Positive range tests
+	vector<pair<string, string>> tests = {
+		{"1.0.0 - 2.0.0", "2.2.3"},
+		{"^1.2.3", "1.2.3-pre"},
+		{"^1.2", "1.2.0-pre"},
+		{"^1.2.3", "1.2.3-beta"},
+		{"=0.7.x", "0.7.0-asdf"},
+		{">=0.7.x", "0.7.0-asdf"},
+		{"1.0.0", "1.0.1"},
+		{">=1.0.0", "0.0.0"},
+		{">=1.0.0", "0.0.1"},
+		{">=1.0.0", "0.1.0"},
+		{">1.0.0", "0.0.1"},
+		{">1.0.0", "0.1.0"},
+		{"<=2.0.0", "3.0.0"},
+		{"<=2.0.0", "2.9999.9999"},
+		{"<=2.0.0", "2.2.9"},
+		{"<2.0.0", "2.9999.9999"},
+		{"<2.0.0", "2.2.9"},
+		{">=0.1.97", "0.1.93"},
+		{"0.1.20 || 1.2.4", "1.2.3"},
+		{">=0.2.3 || <0.0.1", "0.0.3"},
+		{">=0.2.3 || <0.0.1", "0.2.2"},
+		{"\"2.x.x\"", "1.1.3"},
+		{"\"2.x.x\"", "3.1.3"},
+		{"1.2.x", "1.3.3"},
+		{"\"1.2.x\" || \"2.x\"", "3.1.3"},
+		{"\"1.2.x\" || \"2.x\"", "1.1.3"},
+		{"2.*.*", "1.1.3"},
+		{"2.*.*", "3.1.3"},
+		{"1.2.*", "1.3.3"},
+		{"1.2.* || 2.*", "3.1.3"},
+		{"1.2.* || 2.*", "1.1.3"},
+		{"2", "1.1.2"},
+		{"2.3", "2.4.1"},
+		{"~2.4", "2.5.0"}, // >=2.4.0 <2.5.0
+		{"~2.4", "2.3.9"},
+		{"~1", "0.2.3"}, // >=1.0.0 <2.0.0
+		{"~1.0", "1.1.0"}, // >=1.0.0 <1.1.0
+		{"<1", "1.0.0"},
+		{">=1.2", "1.1.1"},
+		{"=0.7.x", "0.8.2"},
+		{">=0.7.x", "0.6.2"},
+		{"<0.7.x", "0.7.2"},
+		{"=1.2.3", "1.2.3-beta"},
+		{">1.2", "1.2.8"},
+		{"^1.2.3", "2.0.0-alpha"},
+		{"^1.2.3", "1.2.2"},
+		{"^1.2", "1.1.9"}
+	};
+	for (auto const& t: tests)
+	{
+		SemVerVersion version(t.second);
+		SemVerMatchExpression expression = parseExpression(t.first);
+		BOOST_CHECK_MESSAGE(
+			!expression.matches(version),
+			"Version \"" + t.second + "\" did satisfy expression \"" + t.first + "\" " +
+			"(although it should not)"
+		);
+	}
+}
+
+BOOST_AUTO_TEST_SUITE_END()
+
+}
+}
+} // end namespaces
diff --git a/test/libsolidity/SolidityABIJSON.cpp b/test/libsolidity/SolidityABIJSON.cpp
index cfc7b9bd..ec621104 100644
--- a/test/libsolidity/SolidityABIJSON.cpp
+++ b/test/libsolidity/SolidityABIJSON.cpp
@@ -39,7 +39,7 @@ public:
 
 	void checkInterface(std::string const& _code, std::string const& _expectedInterfaceString)
 	{
-		ETH_TEST_REQUIRE_NO_THROW(m_compilerStack.parse(_code), "Parsing contract failed");
+		ETH_TEST_REQUIRE_NO_THROW(m_compilerStack.parse("pragma solidity >=0.0;\n" + _code), "Parsing contract failed");
 		std::string generatedInterfaceString = m_compilerStack.metadata("", DocumentationType::ABIInterface);
 		Json::Value generatedInterface;
 		m_reader.parse(generatedInterfaceString, generatedInterface);
diff --git a/test/libsolidity/SolidityExecutionFramework.h b/test/libsolidity/SolidityExecutionFramework.h
index f4bdc657..6cf7e0ee 100644
--- a/test/libsolidity/SolidityExecutionFramework.h
+++ b/test/libsolidity/SolidityExecutionFramework.h
@@ -67,8 +67,10 @@ public:
 		std::map<std::string, Address> const& _libraryAddresses = std::map<std::string, Address>()
 	)
 	{
+		// Silence compiler version warning
+		std::string sourceCode = "pragma solidity >=0.0;\n" + _sourceCode;
 		m_compiler.reset(false);
-		m_compiler.addSource("", _sourceCode);
+		m_compiler.addSource("", sourceCode);
 		if (!m_compiler.compile(m_optimize, m_optimizeRuns))
 		{
 			for (auto const& error: m_compiler.errors())
diff --git a/test/libsolidity/SolidityNameAndTypeResolution.cpp b/test/libsolidity/SolidityNameAndTypeResolution.cpp
index fdd8d7f4..2c126b65 100644
--- a/test/libsolidity/SolidityNameAndTypeResolution.cpp
+++ b/test/libsolidity/SolidityNameAndTypeResolution.cpp
@@ -45,15 +45,17 @@ namespace
 {
 
 pair<ASTPointer<SourceUnit>, std::shared_ptr<Error::Type const>>
-parseAnalyseAndReturnError(string const& _source, bool _reportWarnings = false)
+parseAnalyseAndReturnError(string const& _source, bool _reportWarnings = false, bool _insertVersionPragma = true)
 {
+	// Silence compiler version warning
+	string source = _insertVersionPragma ? "pragma solidity >=0.0;\n" + _source : _source;
 	ErrorList errors;
 	Parser parser(errors);
 	ASTPointer<SourceUnit> sourceUnit;
 	// catch exceptions for a transition period
 	try
 	{
-		sourceUnit = parser.parse(std::make_shared<Scanner>(CharStream(_source)));
+		sourceUnit = parser.parse(std::make_shared<Scanner>(CharStream(source)));
 		if(!sourceUnit)
 			return make_pair(sourceUnit, nullptr);
 
@@ -445,8 +447,8 @@ BOOST_AUTO_TEST_CASE(function_no_implementation)
 		"}\n";
 	ETH_TEST_REQUIRE_NO_THROW(sourceUnit = parseAndAnalyse(text), "Parsing and name Resolving failed");
 	std::vector<ASTPointer<ASTNode>> nodes = sourceUnit->nodes();
-	ContractDefinition* contract = dynamic_cast<ContractDefinition*>(nodes[0].get());
-	BOOST_CHECK(contract);
+	ContractDefinition* contract = dynamic_cast<ContractDefinition*>(nodes[1].get());
+	BOOST_REQUIRE(contract);
 	BOOST_CHECK(!contract->annotation().isFullyImplemented);
 	BOOST_CHECK(!contract->definedFunctions()[0]->isImplemented());
 }
@@ -460,12 +462,12 @@ BOOST_AUTO_TEST_CASE(abstract_contract)
 		)";
 	ETH_TEST_REQUIRE_NO_THROW(sourceUnit = parseAndAnalyse(text), "Parsing and name Resolving failed");
 	std::vector<ASTPointer<ASTNode>> nodes = sourceUnit->nodes();
-	ContractDefinition* base = dynamic_cast<ContractDefinition*>(nodes[0].get());
-	ContractDefinition* derived = dynamic_cast<ContractDefinition*>(nodes[1].get());
-	BOOST_CHECK(base);
+	ContractDefinition* base = dynamic_cast<ContractDefinition*>(nodes[1].get());
+	ContractDefinition* derived = dynamic_cast<ContractDefinition*>(nodes[2].get());
+	BOOST_REQUIRE(base);
 	BOOST_CHECK(!base->annotation().isFullyImplemented);
 	BOOST_CHECK(!base->definedFunctions()[0]->isImplemented());
-	BOOST_CHECK(derived);
+	BOOST_REQUIRE(derived);
 	BOOST_CHECK(derived->annotation().isFullyImplemented);
 	BOOST_CHECK(derived->definedFunctions()[0]->isImplemented());
 }
@@ -479,8 +481,8 @@ BOOST_AUTO_TEST_CASE(abstract_contract_with_overload)
 		)";
 	ETH_TEST_REQUIRE_NO_THROW(sourceUnit = parseAndAnalyse(text), "Parsing and name Resolving failed");
 	std::vector<ASTPointer<ASTNode>> nodes = sourceUnit->nodes();
-	ContractDefinition* base = dynamic_cast<ContractDefinition*>(nodes[0].get());
-	ContractDefinition* derived = dynamic_cast<ContractDefinition*>(nodes[1].get());
+	ContractDefinition* base = dynamic_cast<ContractDefinition*>(nodes[1].get());
+	ContractDefinition* derived = dynamic_cast<ContractDefinition*>(nodes[2].get());
 	BOOST_REQUIRE(base);
 	BOOST_CHECK(!base->annotation().isFullyImplemented);
 	BOOST_REQUIRE(derived);
@@ -527,9 +529,9 @@ BOOST_AUTO_TEST_CASE(abstract_contract_constructor_args_not_provided)
 		)";
 	ETH_TEST_REQUIRE_NO_THROW(sourceUnit = parseAndAnalyse(text), "Parsing and name resolving failed");
 	std::vector<ASTPointer<ASTNode>> nodes = sourceUnit->nodes();
-	BOOST_CHECK_EQUAL(nodes.size(), 3);
-	ContractDefinition* derived = dynamic_cast<ContractDefinition*>(nodes[2].get());
-	BOOST_CHECK(derived);
+	BOOST_CHECK_EQUAL(nodes.size(), 4);
+	ContractDefinition* derived = dynamic_cast<ContractDefinition*>(nodes[3].get());
+	BOOST_REQUIRE(derived);
 	BOOST_CHECK(!derived->annotation().isFullyImplemented);
 }
 
@@ -553,9 +555,9 @@ BOOST_AUTO_TEST_CASE(implement_abstract_via_constructor)
 	)";
 	ETH_TEST_REQUIRE_NO_THROW(sourceUnit = parseAndAnalyse(text), "Parsing and name resolving failed");
 	std::vector<ASTPointer<ASTNode>> nodes = sourceUnit->nodes();
-	BOOST_CHECK_EQUAL(nodes.size(), 2);
-	ContractDefinition* derived = dynamic_cast<ContractDefinition*>(nodes[1].get());
-	BOOST_CHECK(derived);
+	BOOST_CHECK_EQUAL(nodes.size(), 3);
+	ContractDefinition* derived = dynamic_cast<ContractDefinition*>(nodes[2].get());
+	BOOST_REQUIRE(derived);
 	BOOST_CHECK(!derived->annotation().isFullyImplemented);
 }
 
@@ -3853,6 +3855,23 @@ BOOST_AUTO_TEST_CASE(modifier_without_underscore)
 	BOOST_CHECK(expectError(text, true) == Error::Type::SyntaxError);
 }
 
+BOOST_AUTO_TEST_CASE(warn_nonpresent_pragma)
+{
+	char const* text = "contract C {}";
+	auto sourceAndError = parseAnalyseAndReturnError(text, true, false);
+	BOOST_REQUIRE(!!sourceAndError.second);
+	BOOST_REQUIRE(!!sourceAndError.first);
+	BOOST_CHECK(*sourceAndError.second == Error::Type::Warning);
+}
+
+BOOST_AUTO_TEST_CASE(unsatisfied_version)
+{
+	char const* text = R"(
+		pragma solidity ^99.99.0;
+	)";
+	BOOST_CHECK(expectError(text, true) == Error::Type::SyntaxError);
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }
diff --git a/test/libsolidity/SolidityNatspecJSON.cpp b/test/libsolidity/SolidityNatspecJSON.cpp
index 56572b43..1f74e928 100644
--- a/test/libsolidity/SolidityNatspecJSON.cpp
+++ b/test/libsolidity/SolidityNatspecJSON.cpp
@@ -46,7 +46,7 @@ public:
 	)
 	{
 		std::string generatedDocumentationString;
-		ETH_TEST_REQUIRE_NO_THROW(m_compilerStack.parse(_code), "Parsing failed");
+		ETH_TEST_REQUIRE_NO_THROW(m_compilerStack.parse("pragma solidity >=0.0;\n" + _code), "Parsing failed");
 
 		if (_userDocumentation)
 			generatedDocumentationString = m_compilerStack.metadata("", DocumentationType::NatspecUser);