do not consider string types as immut cand.

slither/detectors/variables/unchanged_state_variables.py

@@ -118,8 +118,9 @@ class UnchangedStateVariables:
                         self.constant_candidates.append(v)
 
                     elif (
-                        v in constructor_variables_written or v in variables_initialized
+                        v.type != ElementaryType("string")
-                    ) and version.parse(self.compilation_unit.solc_version) >= version.parse(
+                        and version.parse(self.compilation_unit.solc_version)
-                        "0.6.5"
+                        >= version.parse("0.6.5")
+                        and (v in constructor_variables_written or v in variables_initialized)
                     ):
                         self.immutable_candidates.append(v)

tests/detectors/immutable-states/0.4.25/immut_state_variables.sol

@@ -45,9 +45,11 @@ contract MyConc{
     uint not_constant_2 = getNumber();
     uint not_constant_3 = 10 + block.number;
     uint not_constant_5;
+    string cannote_be_immutable;
     
-	constructor(uint b) public {
+	constructor(uint b, string memory c) public {
 		not_constant_5 = b;
+        cannote_be_immutable = c;
 	}
 
     function getNumber() public returns(uint){

tests/detectors/immutable-states/0.5.16/immut_state_variables.sol

@@ -46,9 +46,11 @@ contract MyConc{
     uint not_constant_2 = getNumber();
     uint not_constant_3 = 10 + block.number;
     uint not_constant_5;
+    string cannote_be_immutable;
     
-	constructor(uint b) public {
+	constructor(uint b, string memory c) public {
 		not_constant_5 = b;
+        cannote_be_immutable = c;
 	}
 
     function getNumber() public returns(uint){

tests/detectors/immutable-states/0.6.11/immut_state_variables.sol

@@ -67,9 +67,11 @@ contract Good {
     uint immutable should_be_immutable_3 = 10 + block.number;
     B immutable should_be_immutable_4 = new B();
     uint immutable should_be_immutable_5;
+    string cannote_be_immutable;
     
-	constructor(uint b) public {
+	constructor(uint b, string memory c) public {
 		should_be_immutable_5 = b;
+        cannote_be_immutable = c;
 	}
 
     function getNumber() public returns(uint){

tests/detectors/immutable-states/0.7.6/immut_state_variables.sol

@@ -66,9 +66,11 @@ contract Good {
     uint immutable should_be_immutable_3 = 10 + block.number;
     B immutable should_be_immutable_4 = new B();
     uint immutable should_be_immutable_5;
+    string cannote_be_immutable;
     
-	constructor(uint b) {
+	constructor(uint b, string memory c) {
 		should_be_immutable_5 = b;
+        cannote_be_immutable = c;
 	}
 
     function getNumber() public returns(uint){

tests/detectors/immutable-states/0.8.0/immut_state_variables.sol

@@ -44,9 +44,11 @@ contract Bad {
     uint should_be_immutable_2 = getNumber();
     uint should_be_immutable_3 = 10 + block.number;
     uint should_be_immutable_5;
+    string cannote_be_immutable;
     
-	constructor(uint b) {
+	constructor(uint b, string memory c) {
 		should_be_immutable_5 = b;
+        cannote_be_immutable = c;
 	}
 
     function getNumber() public returns(uint){

tests/detectors/immutable-states/0.8.0/immut_state_variables.sol.0.8.0.CouldBeImmutable.json

@@ -24,7 +24,7 @@
                             "name": "Bad",
                             "source_mapping": {
                                 "start": 718,
-                                "length": 493,
+                                "length": 577,
                                 "filename_relative": "tests/detectors/immutable-states/0.8.0/immut_state_variables.sol",
                                 "filename_absolute": "/GENERIC_PATH",
                                 "filename_short": "tests/detectors/immutable-states/0.8.0/immut_state_variables.sol",
@@ -49,7 +49,9 @@
                                     53,
                                     54,
                                     55,
-                                    56
+                                    56,
+                                    57,
+                                    58
                                 ],
                                 "starting_column": 1,
                                 "ending_column": 2
@@ -90,7 +92,7 @@
                             "name": "Bad",
                             "source_mapping": {
                                 "start": 718,
-                                "length": 493,
+                                "length": 577,
                                 "filename_relative": "tests/detectors/immutable-states/0.8.0/immut_state_variables.sol",
                                 "filename_absolute": "/GENERIC_PATH",
                                 "filename_short": "tests/detectors/immutable-states/0.8.0/immut_state_variables.sol",
@@ -115,7 +117,9 @@
                                     53,
                                     54,
                                     55,
-                                    56
+                                    56,
+                                    57,
+                                    58
                                 ],
                                 "starting_column": 1,
                                 "ending_column": 2
@@ -156,7 +160,7 @@
                             "name": "Bad",
                             "source_mapping": {
                                 "start": 718,
-                                "length": 493,
+                                "length": 577,
                                 "filename_relative": "tests/detectors/immutable-states/0.8.0/immut_state_variables.sol",
                                 "filename_absolute": "/GENERIC_PATH",
                                 "filename_short": "tests/detectors/immutable-states/0.8.0/immut_state_variables.sol",
@@ -181,7 +185,9 @@
                                     53,
                                     54,
                                     55,
-                                    56
+                                    56,
+                                    57,
+                                    58
                                 ],
                                 "starting_column": 1,
                                 "ending_column": 2
@@ -222,7 +228,7 @@
                             "name": "Bad",
                             "source_mapping": {
                                 "start": 718,
-                                "length": 493,
+                                "length": 577,
                                 "filename_relative": "tests/detectors/immutable-states/0.8.0/immut_state_variables.sol",
                                 "filename_absolute": "/GENERIC_PATH",
                                 "filename_short": "tests/detectors/immutable-states/0.8.0/immut_state_variables.sol",
@@ -247,7 +253,9 @@
                                     53,
                                     54,
                                     55,
-                                    56
+                                    56,
+                                    57,
+                                    58
                                 ],
                                 "starting_column": 1,
                                 "ending_column": 2