Type checking for pure expressions.

3 files changed, 18 insertions, 0 deletions

diff --git a/libsolidity/ast/ASTAnnotations.h b/libsolidity/ast/ASTAnnotations.h
index 9c4c3ae8..bd297f9e 100644
--- a/libsolidity/ast/ASTAnnotations.h
+++ b/libsolidity/ast/ASTAnnotations.h
@@ -156,6 +156,8 @@ struct ExpressionAnnotation: ASTAnnotation
 	TypePointer type;
 	/// Whether the expression is a constant variable
 	bool isConstant = false;
+	/// Whether the expression is pure, i.e. compile-time constant.
+	bool isPure = false;
 	/// Whether it is an LValue (i.e. something that can be assigned to).
 	bool isLValue = false;
 	/// Whether the expression is used in a context where the LValue is actually required.
diff --git a/libsolidity/ast/Types.cpp b/libsolidity/ast/Types.cpp
index d2793b6d..0e11c3ec 100644
--- a/libsolidity/ast/Types.cpp
+++ b/libsolidity/ast/Types.cpp
@@ -2456,6 +2456,18 @@ u256 FunctionType::externalIdentifier() const
 	return FixedHash<4>::Arith(FixedHash<4>(dev::keccak256(externalSignature())));
 }
 
+bool FunctionType::isPure() const
+{
+	return
+		m_location == Location::SHA3 ||
+		m_location == Location::ECRecover ||
+		m_location == Location::SHA256 ||
+		m_location == Location::RIPEMD160 ||
+		m_location == Location::AddMod ||
+		m_location == Location::MulMod ||
+		m_location == Location::ObjectCreation;
+}
+
 TypePointers FunctionType::parseElementaryTypeVector(strings const& _types)
 {
 	TypePointers pointers;
diff --git a/libsolidity/ast/Types.h b/libsolidity/ast/Types.h
index 022b67c4..7c8fd429 100644
--- a/libsolidity/ast/Types.h
+++ b/libsolidity/ast/Types.h
@@ -972,6 +972,10 @@ public:
 	}
 	bool hasDeclaration() const { return !!m_declaration; }
 	bool isConstant() const { return m_isConstant; }
+	/// @returns true if the the result of this function only depends on its arguments
+	/// and it does not modify the state.
+	/// Currently, this will only return true for internal functions like keccak and ecrecover.
+	bool isPure() const;
 	bool isPayable() const { return m_isPayable; }
 	/// @return A shared pointer of an ASTString.
 	/// Can contain a nullptr in which case indicates absence of documentation