Make LintExpectationId stable between compilation sessions (RFC-2383)

compiler/rustc_middle/src/lint.rs

@@ -6,10 +6,9 @@ use rustc_errors::{Diagnostic, DiagnosticBuilder, DiagnosticId};
 use rustc_hir::HirId;
 use rustc_index::vec::IndexVec;
 use rustc_query_system::ich::StableHashingContext;
-use rustc_session::lint::LintExpectationId;
 use rustc_session::lint::{
     builtin::{self, FORBIDDEN_LINT_GROUPS},
-    FutureIncompatibilityReason, Level, Lint, LintId,
+    FutureIncompatibilityReason, Level, Lint, LintExpectationId, LintId,
 };
 use rustc_session::{DiagnosticMessageId, Session};
 use rustc_span::hygiene::MacroKind;

compiler/rustc_middle/src/ty/context.rs

@@ -49,7 +49,7 @@ use rustc_middle::mir::FakeReadCause;
 use rustc_query_system::ich::{NodeIdHashingMode, StableHashingContext};
 use rustc_serialize::opaque::{FileEncodeResult, FileEncoder};
 use rustc_session::config::{BorrowckMode, CrateType, OutputFilenames};
-use rustc_session::lint::{Level, Lint};
+use rustc_session::lint::{Level, Lint, LintExpectationId};
 use rustc_session::Limit;
 use rustc_session::Session;
 use rustc_span::def_id::{DefPathHash, StableCrateId};
@@ -2755,11 +2755,13 @@ impl<'tcx> TyCtxt<'tcx> {
                 return bound;
             }
 
-            if hir
-                .attrs(id)
-                .iter()
-                .any(|attr| Level::from_symbol(attr.name_or_empty(), attr.id.as_u32()).is_some())
-            {
+            if hir.attrs(id).iter().enumerate().any(|(attr_index, attr)| {
+                Level::from_symbol(attr.name_or_empty(), || LintExpectationId::Stable {
+                    hir_id: id,
+                    attr_index,
+                })
+                .is_some()
+            }) {
                 return id;
             }
             let next = hir.get_parent_node(id);