Fix reads checks for immutable variables.

Changelog.md

@@ -13,6 +13,7 @@ Compiler Features:
 
 Bugfixes:
  * AST: Remove ``null`` member values also when the compiler is used in standard-json-mode.
+ * Immutables: Properly treat complex assignment and increment/decrement as both reading and writing and thus disallow it everywhere for immutable variables.
  * Optimizer: Keep side-effects of ``x`` in ``byte(a, shr(b, x))`` even if the constants ``a`` and ``b`` would make the expression zero unconditionally. This optimizer rule is very hard if not impossible to trigger in a way that it can result in invalid code, though.
  * SMTChecker: Fix internal error in BMC function inlining.
  * SMTChecker: Fix internal error on array implicit conversion.

libsolidity/analysis/ImmutableValidator.cpp

@@ -163,41 +163,44 @@ void ImmutableValidator::analyseVariableReference(VariableDeclaration const& _va
 	if (!_variableReference.isStateVariable() || !_variableReference.immutable())
 		return;
 
-	if (_expression.annotation().willBeWrittenTo && _expression.annotation().lValueOfOrdinaryAssignment)
+	// If this is not an ordinary assignment, we write and read at the same time.
+	bool write = _expression.annotation().willBeWrittenTo;
+	bool read = !_expression.annotation().willBeWrittenTo || !_expression.annotation().lValueOfOrdinaryAssignment;
+	if (write)
 	{
 		if (!m_currentConstructor)
 			m_errorReporter.typeError(
 				1581_error,
 				_expression.location(),
-				"Immutable variables can only be initialized inline or assigned directly in the constructor."
+				"Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor."
 			);
 		else if (m_currentConstructor->annotation().contract->id() != _variableReference.annotation().contract->id())
 			m_errorReporter.typeError(
 				7484_error,
 				_expression.location(),
-				"Immutable variables must be initialized in the constructor of the contract they are defined in."
+				"Cannot write to immutable here: Immutable variables must be initialized in the constructor of the contract they are defined in."
 			);
 		else if (m_inLoop)
 			m_errorReporter.typeError(
 				6672_error,
 				_expression.location(),
-				"Immutable variables can only be initialized once, not in a while statement."
+				"Cannot write to immutable here: Immutable variables cannot be initialized inside a loop."
 			);
 		else if (m_inBranch)
 			m_errorReporter.typeError(
 				4599_error,
 				_expression.location(),
-				"Immutable variables must be initialized unconditionally, not in an if statement."
+				"Cannot write to immutable here: Immutable variables cannot be initialized inside an if statement."
 			);
-
-		if (!m_initializedStateVariables.emplace(&_variableReference).second)
+		else if (m_initializedStateVariables.count(&_variableReference))
 			m_errorReporter.typeError(
 				1574_error,
 				_expression.location(),
 				"Immutable state variable already initialized."
 			);
+		m_initializedStateVariables.emplace(&_variableReference);
 	}
-	else if (m_inConstructionContext)
+	if (read && m_inConstructionContext)
 		m_errorReporter.typeError(
 			7733_error,
 			_expression.location(),

test/libsolidity/syntaxTests/immutable/complex.sol

@@ -0,0 +1,8 @@
+contract A {
+  int immutable a;
+  constructor() { a = 5; }
+  function f() public { a += 7; }
+}
+
+// ----
+// TypeError 1581: (83-84): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/conditionally_initialized.sol

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

test/libsolidity/syntaxTests/immutable/ctor_indirect_initialization.sol

@@ -9,4 +9,4 @@ contract C {
     }
 }
 // ----
-// TypeError 1581: (119-120): Immutable variables can only be initialized inline or assigned directly in the constructor.
+// TypeError 1581: (119-120): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/ctor_modifier_args.sol

@@ -9,4 +9,4 @@ contract C {
     function f(uint a) internal pure {}
 }
 // ----
-// TypeError 1581: (59-60): Immutable variables can only be initialized inline or assigned directly in the constructor.
+// TypeError 1581: (59-60): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/ctor_modifier_initialization.sol

@@ -8,4 +8,4 @@ contract C {
     }
 }
 // ----
-// TypeError 1581: (102-103): Immutable variables can only be initialized inline or assigned directly in the constructor.
+// TypeError 1581: (102-103): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/decrement.sol

@@ -1,8 +1,8 @@
 contract C {
-    uint immutable x = 3;
+    uint immutable x;
     constructor() {
         x--;
     }
 }
 // ----
-// TypeError 7733: (67-68): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.
+// TypeError 7733: (63-64): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.

test/libsolidity/syntaxTests/immutable/delete.sol

@@ -1,8 +1,8 @@
 contract C {
-    uint immutable x = 3;
+    uint immutable x;
     constructor() {
         delete x;
     }
 }
 // ----
-// TypeError 7733: (74-75): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.
+// TypeError 7733: (70-71): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.

test/libsolidity/syntaxTests/immutable/delete_and_initialize.sol

@@ -0,0 +1,9 @@
+contract C {
+    uint immutable x = 3;
+    constructor() {
+        delete x;
+    }
+}
+// ----
+// TypeError 1574: (74-75): Immutable state variable already initialized.
+// TypeError 7733: (74-75): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.

test/libsolidity/syntaxTests/immutable/function_pointer_initializing.sol

@@ -10,5 +10,4 @@ contract C is B(C.f) {
     function f() internal returns(uint) { return x = 2; }
 }
 // ----
-// TypeError 1581: (200-201): Immutable variables can only be initialized inline or assigned directly in the constructor.
-// TypeError 1574: (200-201): Immutable state variable already initialized.
+// TypeError 1581: (200-201): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/increment.sol

@@ -1,8 +1,8 @@
 contract C {
-    uint immutable x = 3;
+    uint immutable x;
     constructor() {
         x++;
     }
 }
 // ----
-// TypeError 7733: (67-68): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.
+// TypeError 7733: (63-64): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.

test/libsolidity/syntaxTests/immutable/increment_decrement.sol

@@ -0,0 +1,11 @@
+contract C {
+  uint immutable x;
+  uint immutable y;
+  constructor() {
+    ++x;
+    --y;
+  }
+}
+// ----
+// TypeError 7733: (77-78): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.
+// TypeError 7733: (86-87): Immutable variables cannot be read during contract creation time, which means they cannot be read in the constructor or any function or modifier called from it.

test/libsolidity/syntaxTests/immutable/inheritance_ctor_argument.sol

@@ -11,4 +11,4 @@ contract C is B {
     constructor() B(y = 3) { }
 }
 // ----
-// TypeError 1581: (148-149): Immutable variables can only be initialized inline or assigned directly in the constructor.
+// TypeError 1581: (148-149): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/inheritance_ctor_inherit_specifier_argument_init.sol

@@ -10,4 +10,4 @@ contract C is B(C.y = 3) {
     uint immutable y;
 }
 // ----
-// TypeError 1581: (104-107): Immutable variables can only be initialized inline or assigned directly in the constructor.
+// TypeError 1581: (104-107): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/inheritance_wrong_ctor.sol

@@ -8,5 +8,4 @@ contract C is B {
     }
 }
 // ----
-// TypeError 7484: (88-89): Immutable variables must be initialized in the constructor of the contract they are defined in.
-// TypeError 1574: (88-89): Immutable state variable already initialized.
+// TypeError 7484: (88-89): Cannot write to immutable here: Immutable variables must be initialized in the constructor of the contract they are defined in.

test/libsolidity/syntaxTests/immutable/loop_initialized.sol

@@ -6,4 +6,4 @@ contract C {
     }
 }
 // ----
-// TypeError 6672: (88-89): Immutable variables can only be initialized once, not in a while statement.
+// TypeError 6672: (88-89): Cannot write to immutable here: Immutable variables cannot be initialized inside a loop.

test/libsolidity/syntaxTests/immutable/unary.sol

@@ -0,0 +1,8 @@
+contract A {
+  int immutable a;
+  constructor() { a = 5; }
+  function f() public { --a; }
+}
+
+// ----
+// TypeError 1581: (85-86): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/writing_after_initialization.sol

@@ -6,5 +6,4 @@ contract C {
     }
 }
 // ----
-// TypeError 1581: (76-77): Immutable variables can only be initialized inline or assigned directly in the constructor.
-// TypeError 1574: (76-77): Immutable state variable already initialized.
+// TypeError 1581: (76-77): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.

test/libsolidity/syntaxTests/immutable/writing_after_initialization_modifier.sol

@@ -8,5 +8,4 @@ contract C {
     }
 }
 // ----
-// TypeError 1581: (111-112): Immutable variables can only be initialized inline or assigned directly in the constructor.
-// TypeError 1574: (111-112): Immutable state variable already initialized.
+// TypeError 1581: (111-112): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.