Disallow assigning to fields of non-mutable structs (FuelLabs#1420)

* Disallow assigning to fields of non-mutable structs

* Add test for assigning to field of non-mutable struct

* fix broken test case that was failing with mutability check

* disable broken test blocked on FuelLabs#1188

* disable impl_self_reassignment test

This test was failing by trying to assign to a non-mut variable. We need
`&mut self` methods before it can be re-enabled.

Co-authored-by: Alex Hansen <[email protected]>

sway-core/src/semantic_analysis/ast_node/mod.rs

@@ -961,6 +961,30 @@ fn reassignment(
 
                         match expr {
                             Expression::VariableExpression { name, .. } => {
+                                match namespace.clone().resolve_symbol(&name).value {
+                                    Some(TypedDeclaration::VariableDeclaration(
+                                        TypedVariableDeclaration { is_mutable, .. },
+                                    )) => {
+                                        if !is_mutable.is_mutable() {
+                                            errors.push(CompileError::AssignmentToNonMutable {
+                                                name: name.clone(),
+                                            });
+                                        }
+                                    }
+                                    Some(other) => {
+                                        errors.push(CompileError::ReassignmentToNonVariable {
+                                            name: name.clone(),
+                                            kind: other.friendly_name(),
+                                            span,
+                                        });
+                                        return err(warnings, errors);
+                                    }
+                                    None => {
+                                        errors
+                                            .push(CompileError::UnknownVariable { var_name: name });
+                                        return err(warnings, errors);
+                                    }
+                                }
                                 names_vec.push(ReassignmentLhs {
                                     name,
                                     r#type: type_checked.return_type,

test/src/e2e_vm_tests/mod.rs

@@ -293,10 +293,16 @@ pub fn run(filter_regex: Option<regex::Regex>) {
             "should_pass/language/contract_caller_as_type",
             ProgramState::Return(42),
         ),
+        /*
+         * This test is disabled because in order to work correctly it requires that we implement
+         * `&mut self` methods.
+         *
+         * See: #1188
         (
             "should_pass/language/self_impl_reassignment",
             ProgramState::Return(1),
         ),
+        */
         (
             "should_pass/language/import_trailing_comma",
             ProgramState::Return(0),
@@ -455,6 +461,7 @@ pub fn run(filter_regex: Option<regex::Regex>) {
         "should_fail/double_underscore_var",
         "should_fail/double_underscore_struct",
         "should_fail/double_underscore_enum",
+        "should_fail/assign_to_field_of_non_mutable_struct",
         "should_fail/abi_method_signature_mismatch",
         "should_fail/trait_method_signature_mismatch",
         "should_fail/impure_read_calls_impure_write",

test/src/e2e_vm_tests/test_programs/should_fail/assign_to_field_of_non_mutable_struct/Forc.lock

@@ -0,0 +1,3 @@
+[[package]]
+name = 'assign_to_field_of_non_mutable_struct'
+dependencies = []

test/src/e2e_vm_tests/test_programs/should_fail/assign_to_field_of_non_mutable_struct/Forc.toml

@@ -0,0 +1,6 @@
+[project]
+authors = ["Fuel Labs <[email protected]>"]
+license = "Apache-2.0"
+name = "assign_to_field_of_non_mutable_struct"
+entry = "main.sw"
+implicit-std = false

test/src/e2e_vm_tests/test_programs/should_fail/assign_to_field_of_non_mutable_struct/src/main.sw

@@ -0,0 +1,11 @@
+script;
+
+struct S {
+    x: u64,
+}
+
+fn wow() {
+    let thing: S = S { x: 0 };
+    thing.x = 23;
+}
+

test/src/e2e_vm_tests/test_programs/should_pass/language/nested_structs/src/main.sw

@@ -42,7 +42,7 @@ struct S {
 }
 
 fn main() -> bool {
-    let s = S {
+    let mut s = S {
         t0: W {
             t5: 5,
             t6: T6 {