librustc: Implement a lint mode for mutable structures; deny by default

Author: pcwalton

src/libcore/core.rc

@@ -51,6 +51,7 @@ Implicitly, all crates behave as if they included the following prologue:
 #[warn(vecs_implicitly_copyable)];
 #[deny(non_camel_case_types)];
 #[allow(deprecated_self)];
+#[allow(deprecated_mutable_fields)];
 
 /* The Prelude. */
 

src/librustc/middle/lint.rs

@@ -81,6 +81,7 @@ pub enum lint {
     type_limits,
     default_methods,
     deprecated_self,
+    deprecated_mutable_fields,
 
     managed_heap_memory,
     owned_heap_memory,
@@ -255,6 +256,13 @@ pub fn get_lint_dict() -> LintDict {
             default: warn
          }),
 
+        (@~"deprecated_mutable_fields",
+         @LintSpec {
+            lint: deprecated_mutable_fields,
+            desc: "deprecated mutable fields in structures",
+            default: deny
+        }),
+
         /* FIXME(#3266)--make liveness warnings lintable
         (@~"unused_variable",
          @LintSpec {
@@ -488,6 +496,7 @@ fn check_item(i: @ast::item, cx: ty::ctxt) {
     check_item_type_limits(cx, i);
     check_item_default_methods(cx, i);
     check_item_deprecated_self(cx, i);
+    check_item_deprecated_mutable_fields(cx, i);
 }
 
 // Take a visitor, and modify it so that it will not proceed past subitems.
@@ -705,6 +714,26 @@ fn check_item_deprecated_self(cx: ty::ctxt, item: @ast::item) {
     }
 }
 
+fn check_item_deprecated_mutable_fields(cx: ty::ctxt, item: @ast::item) {
+    match item.node {
+        ast::item_struct(struct_def, _) => {
+            for struct_def.fields.each |field| {
+                match field.node.kind {
+                    ast::named_field(_, ast::struct_mutable, _) => {
+                        cx.sess.span_lint(deprecated_mutable_fields,
+                                          item.id,
+                                          item.id,
+                                          field.span,
+                                          ~"mutable fields are deprecated");
+                    }
+                    ast::named_field(*) | ast::unnamed_field => {}
+                }
+            }
+        }
+        _ => {}
+    }
+}
+
 fn check_item_structural_records(cx: ty::ctxt, it: @ast::item) {
     let visit = item_stopping_visitor(
         visit::mk_simple_visitor(@visit::SimpleVisitor {

src/libstd/std.rc

@@ -29,6 +29,7 @@ not required in or otherwise suitable for the core library.
 #[allow(vecs_implicitly_copyable)];
 #[deny(non_camel_case_types)];
 #[allow(deprecated_self)];
+#[allow(deprecated_mutable_fields)];
 
 #[no_core];