Disallow initialization of immutables in for loops and ternary expressions

Changelog.md

@@ -9,6 +9,7 @@ Compiler Features:
 
 
 Bugfixes:
+ * Immutables: Disallow initialization of immutables in for loops and ternary expressions.
  * SMTChecker: Fix encoding of side-effects inside ``if`` and ``ternary conditional``statements in the BMC engine.
 
 

libsolidity/analysis/ImmutableValidator.cpp

@@ -73,6 +73,16 @@ bool ImmutableValidator::visit(Assignment const& _assignment)
 	return false;
 }
 
+bool ImmutableValidator::visit(Conditional const& _conditional)
+{
+	ScopedSaveAndRestore branchGuard{m_inBranch, true};
+
+	_conditional.condition().accept(*this);
+	_conditional.trueExpression().accept(*this);
+	_conditional.falseExpression().accept(*this);
+
+	return false;
+}
 
 bool ImmutableValidator::visit(FunctionDefinition const& _functionDefinition)
 {
@@ -132,6 +142,21 @@ bool ImmutableValidator::visit(WhileStatement const& _whileStatement)
 	return false;
 }
 
+bool ImmutableValidator::visit(ForStatement const& _forStatement)
+{
+	ScopedSaveAndRestore forLoopGuard{m_inLoop, true};
+
+	if (auto&& initializationExpression = _forStatement.initializationExpression())
+		initializationExpression->accept(*this);
+	if (auto&& condition = _forStatement.condition())
+		condition->accept(*this);
+	if (auto&& loopExpression = _forStatement.loopExpression())
+		loopExpression->accept(*this);
+	_forStatement.body().accept(*this);
+
+	return false;
+}
+
 bool ImmutableValidator::visit(TryStatement const& _tryStatement)
 {
 	ScopedSaveAndRestore constructorGuard{m_inTryStatement, true};
@@ -228,7 +253,7 @@ void ImmutableValidator::analyseVariableReference(VariableDeclaration const& _va
 			m_errorReporter.typeError(
 				4599_error,
 				_expression.location(),
-				"Cannot write to immutable here: Immutable variables cannot be initialized inside an if statement."
+				"Cannot write to immutable here: Immutable variables cannot be initialized inside a conditional (if/ternary) statement."
 			);
 		else if (m_inTryStatement)
 			m_errorReporter.typeError(

libsolidity/analysis/ImmutableValidator.h

@@ -50,11 +50,13 @@ public:
 
 private:
 	bool visit(Assignment const& _assignment);
+	bool visit(Conditional const& _conditional);
 	bool visit(FunctionDefinition const& _functionDefinition);
 	bool visit(ModifierDefinition const& _modifierDefinition);
 	bool visit(MemberAccess const& _memberAccess);
 	bool visit(IfStatement const& _ifStatement);
 	bool visit(WhileStatement const& _whileStatement);
+	bool visit(ForStatement const& _forStatement);
 	bool visit(TryStatement const& _tryStatement);
 	void endVisit(IdentifierPath const& _identifierPath);
 	void endVisit(Identifier const& _identifier);

test/libsolidity/syntaxTests/immutable/conditionally_initialized.sol

@@ -6,4 +6,4 @@ contract C {
     }
 }
 // ----
-// TypeError 4599: (86-87): Cannot write to immutable here: Immutable variables cannot be initialized inside an if statement.
+// TypeError 4599: (86-87): Cannot write to immutable here: Immutable variables cannot be initialized inside a conditional (if/ternary) statement.

test/libsolidity/syntaxTests/immutable/for_loop_initialized.sol

@@ -0,0 +1,12 @@
+contract C {
+    uint immutable x;
+    constructor() {
+        for (x = 1; x < 10; ++x)
+            x = 5;
+    }
+}
+
+// ----
+// TypeError 6672: (68-69): Cannot write to immutable here: Immutable variables cannot be initialized inside a loop.
+// TypeError 6672: (85-86): Cannot write to immutable here: Immutable variables cannot be initialized inside a loop.
+// TypeError 6672: (100-101): Cannot write to immutable here: Immutable variables cannot be initialized inside a loop.

test/libsolidity/syntaxTests/immutable/ternary_initialized.sol

@@ -0,0 +1,15 @@
+contract A
+{
+    uint256 immutable x;
+    uint256 y = 0;
+
+    constructor(bool _branch)
+    {
+        _branch ? x = 1 : y = 2;
+        _branch ? y = 3 : x = 4;
+    }
+}
+
+// ----
+// TypeError 4599: (112-113): Cannot write to immutable here: Immutable variables cannot be initialized inside a conditional (if/ternary) statement.
+// TypeError 4599: (153-154): Cannot write to immutable here: Immutable variables cannot be initialized inside a conditional (if/ternary) statement.