Merge pull request #14198 from ethereum/disallow-immutable-initialization-in-try-catch

Disallow immutable initialization in try catch statements

Changelog.md

@@ -22,6 +22,7 @@ Bugfixes:
  * Antlr Grammar: Fix discrepancy with the parser, which allowed octal numbers.
  * Antlr Grammar: Fix of a discrepancy with the parser, which allowed numbers followed by an identifier with no whitespace.
  * Antlr Grammar: Stricter rules for function definitions. The grammar will no longer accept as valid free functions having specifiers which are exclusive to contract functions.
+ * Immutables: Disallow initialization of immutables in try/catch statements.
  * SMTChecker: Fix false positives in ternary operators that contain verification targets in its branches, directly or indirectly.
 
 

libsolidity/analysis/ImmutableValidator.cpp

@@ -132,6 +132,19 @@ bool ImmutableValidator::visit(WhileStatement const& _whileStatement)
 	return false;
 }
 
+bool ImmutableValidator::visit(TryStatement const& _tryStatement)
+{
+	ScopedSaveAndRestore constructorGuard{m_inTryStatement, true};
+
+	_tryStatement.externalCall().accept(*this);
+
+	for (auto&& clause: _tryStatement.clauses())
+		if (clause)
+			clause->accept(*this);
+
+	return false;
+}
+
 void ImmutableValidator::endVisit(IdentifierPath const& _identifierPath)
 {
 	if (auto const callableDef = dynamic_cast<CallableDeclaration const*>(_identifierPath.annotation().referencedDeclaration))
@@ -217,6 +230,12 @@ void ImmutableValidator::analyseVariableReference(VariableDeclaration const& _va
 				_expression.location(),
 				"Cannot write to immutable here: Immutable variables cannot be initialized inside an if statement."
 			);
+		else if (m_inTryStatement)
+			m_errorReporter.typeError(
+					4130_error,
+					_expression.location(),
+					"Cannot write to immutable here: Immutable variables cannot be initialized inside a try/catch statement."
+			);
 		else if (m_initializedStateVariables.count(&_variableReference))
 		{
 			if (!read)

libsolidity/analysis/ImmutableValidator.h

@@ -55,6 +55,7 @@ private:
 	bool visit(MemberAccess const& _memberAccess);
 	bool visit(IfStatement const& _ifStatement);
 	bool visit(WhileStatement const& _whileStatement);
+	bool visit(TryStatement const& _tryStatement);
 	void endVisit(IdentifierPath const& _identifierPath);
 	void endVisit(Identifier const& _identifier);
 	void endVisit(Return const& _return);
@@ -78,6 +79,7 @@ private:
 	bool m_inLoop = false;
 	bool m_inBranch = false;
 	bool m_inCreationContext = true;
+	bool m_inTryStatement = false;
 };
 
 }

test/libsolidity/syntaxTests/immutable/try_catch_initialized.sol

@@ -0,0 +1,42 @@
+contract A
+{
+    uint256 public immutable variable;
+
+    constructor()
+    {
+        B b;
+        try b.foo(variable = 1)
+        {
+            variable = 2;
+        }
+        catch Panic(uint)
+        {
+            variable = 3;
+        }
+        catch Error(string memory)
+        {
+            variable = 4;
+        }
+        catch
+        {
+            variable = 5;
+        }
+    }
+}
+
+contract B
+{
+    function foo(uint256) external pure
+    {
+        revert();
+    }
+}
+
+// ====
+// EVMVersion: >=byzantium
+// ----
+// TypeError 4130: (108-116): Cannot write to immutable here: Immutable variables cannot be initialized inside a try/catch statement.
+// TypeError 4130: (144-152): Cannot write to immutable here: Immutable variables cannot be initialized inside a try/catch statement.
+// TypeError 4130: (216-224): Cannot write to immutable here: Immutable variables cannot be initialized inside a try/catch statement.
+// TypeError 4130: (297-305): Cannot write to immutable here: Immutable variables cannot be initialized inside a try/catch statement.
+// TypeError 4130: (357-365): Cannot write to immutable here: Immutable variables cannot be initialized inside a try/catch statement.