Auto merge of #73751 - eddyb:no-empty-tables, r=nikomatsakis

Remove `TypeckTables::empty(None)` and make hir_owner non-optional.

Each commit before the last one removes uses of `TypeckTables::empty(None)`, replacing the empty tables with having `Option` around the `&'tcx TypeckTables<'tcx>` that HIR visitors kept track of.

The last commit removes the concept of "empty `TypeckTables`" altogether, guaranteeing that every `TypeckTables` corresponds to a HIR body owner.

r? @nikomatsakis

src/librustc_driver/lib.rs

@@ -6,6 +6,7 @@
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![feature(nll)]
+#![cfg_attr(bootstrap, feature(track_caller))]
 #![recursion_limit = "256"]
 
 #[macro_use]

src/librustc_driver/pretty.rs

@@ -80,8 +80,7 @@ where
         PpmTyped => {
             abort_on_err(tcx.analysis(LOCAL_CRATE), tcx.sess);
 
-            let empty_tables = ty::TypeckTables::empty(None);
-            let annotation = TypedAnnotation { tcx, tables: Cell::new(&empty_tables) };
+            let annotation = TypedAnnotation { tcx, maybe_typeck_tables: Cell::new(None) };
             tcx.dep_graph.with_ignore(|| f(&annotation, tcx.hir().krate()))
         }
         _ => panic!("Should use call_with_pp_support"),
@@ -304,12 +303,22 @@ impl<'a> pprust::PpAnn for HygieneAnnotation<'a> {
     }
 }
 
-struct TypedAnnotation<'a, 'tcx> {
+struct TypedAnnotation<'tcx> {
     tcx: TyCtxt<'tcx>,
-    tables: Cell<&'a ty::TypeckTables<'tcx>>,
+    maybe_typeck_tables: Cell<Option<&'tcx ty::TypeckTables<'tcx>>>,
 }
 
-impl<'b, 'tcx> HirPrinterSupport<'tcx> for TypedAnnotation<'b, 'tcx> {
+impl<'tcx> TypedAnnotation<'tcx> {
+    /// Gets the type-checking side-tables for the current body.
+    /// As this will ICE if called outside bodies, only call when working with
+    /// `Expr` or `Pat` nodes (they are guaranteed to be found only in bodies).
+    #[track_caller]
+    fn tables(&self) -> &'tcx ty::TypeckTables<'tcx> {
+        self.maybe_typeck_tables.get().expect("`TypedAnnotation::tables` called outside of body")
+    }
+}
+
+impl<'tcx> HirPrinterSupport<'tcx> for TypedAnnotation<'tcx> {
     fn sess(&self) -> &Session {
         &self.tcx.sess
     }
@@ -327,15 +336,15 @@ impl<'b, 'tcx> HirPrinterSupport<'tcx> for TypedAnnotation<'b, 'tcx> {
     }
 }
 
-impl<'a, 'tcx> pprust_hir::PpAnn for TypedAnnotation<'a, 'tcx> {
+impl<'tcx> pprust_hir::PpAnn for TypedAnnotation<'tcx> {
     fn nested(&self, state: &mut pprust_hir::State<'_>, nested: pprust_hir::Nested) {
-        let old_tables = self.tables.get();
+        let old_maybe_typeck_tables = self.maybe_typeck_tables.get();
         if let pprust_hir::Nested::Body(id) = nested {
-            self.tables.set(self.tcx.body_tables(id));
+            self.maybe_typeck_tables.set(Some(self.tcx.body_tables(id)));
         }
         let pp_ann = &(&self.tcx.hir() as &dyn hir::intravisit::Map<'_>);
         pprust_hir::PpAnn::nested(pp_ann, state, nested);
-        self.tables.set(old_tables);
+        self.maybe_typeck_tables.set(old_maybe_typeck_tables);
     }
     fn pre(&self, s: &mut pprust_hir::State<'_>, node: pprust_hir::AnnNode<'_>) {
         if let pprust_hir::AnnNode::Expr(_) = node {
@@ -347,7 +356,7 @@ impl<'a, 'tcx> pprust_hir::PpAnn for TypedAnnotation<'a, 'tcx> {
             s.s.space();
             s.s.word("as");
             s.s.space();
-            s.s.word(self.tables.get().expr_ty(expr).to_string());
+            s.s.word(self.tables().expr_ty(expr).to_string());
             s.pclose();
         }
     }

src/librustc_infer/infer/error_reporting/mod.rs

@@ -1684,7 +1684,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         // Attempt to obtain the span of the parameter so we can
         // suggest adding an explicit lifetime bound to it.
         let generics =
-            self.in_progress_tables.and_then(|table| table.borrow().hir_owner).map(|table_owner| {
+            self.in_progress_tables.map(|table| table.borrow().hir_owner).map(|table_owner| {
                 let hir_id = hir.as_local_hir_id(table_owner);
                 let parent_id = hir.get_parent_item(hir_id);
                 (

src/librustc_infer/infer/mod.rs

@@ -588,7 +588,7 @@ impl<'tcx> InferCtxtBuilder<'tcx> {
     /// Used only by `rustc_typeck` during body type-checking/inference,
     /// will initialize `in_progress_tables` with fresh `TypeckTables`.
     pub fn with_fresh_in_progress_tables(mut self, table_owner: LocalDefId) -> Self {
-        self.fresh_tables = Some(RefCell::new(ty::TypeckTables::empty(Some(table_owner))));
+        self.fresh_tables = Some(RefCell::new(ty::TypeckTables::new(table_owner)));
         self
     }
 

src/librustc_lint/builtin.rs

@@ -165,7 +165,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
                 .pat_ty(pat)
                 .ty_adt_def()
                 .expect("struct pattern type is not an ADT")
-                .variant_of_res(cx.tables().qpath_res(qpath, pat.hir_id));
+                .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
             for fieldpat in field_pats {
                 if fieldpat.is_shorthand {
                     continue;
@@ -901,7 +901,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MutableTransmutes {
             expr: &hir::Expr<'_>,
         ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
             let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
-                cx.tables().qpath_res(qpath, expr.hir_id)
+                cx.qpath_res(qpath, expr.hir_id)
             } else {
                 return None;
             };
@@ -1891,7 +1891,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
             if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
                 // Find calls to `mem::{uninitialized,zeroed}` methods.
                 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
-                    let def_id = cx.tables().qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
+                    let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
 
                     if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
                         return Some(InitKind::Zeroed);
@@ -1911,8 +1911,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
                     // See if the `self` parameter is one of the dangerous constructors.
                     if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
                         if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
-                            let def_id =
-                                cx.tables().qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
+                            let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
 
                             if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
                                 return Some(InitKind::Zeroed);

src/librustc_lint/context.rs

@@ -24,6 +24,7 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync;
 use rustc_errors::{struct_span_err, Applicability};
 use rustc_hir as hir;
+use rustc_hir::def::Res;
 use rustc_hir::def_id::{CrateNum, DefId};
 use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
 use rustc_middle::lint::LintDiagnosticBuilder;
@@ -427,15 +428,12 @@ pub struct LateContext<'a, 'tcx> {
     /// Current body, or `None` if outside a body.
     pub enclosing_body: Option<hir::BodyId>,
 
-    /// Type-checking side-tables for the current body. Access using the
-    /// `tables` method, which handles querying the tables on demand.
+    /// Type-checking side-tables for the current body. Access using the `tables`
+    /// and `maybe_tables` methods, which handle querying the tables on demand.
     // FIXME(eddyb) move all the code accessing internal fields like this,
     // to this module, to avoid exposing it to lint logic.
     pub(super) cached_typeck_tables: Cell<Option<&'tcx ty::TypeckTables<'tcx>>>,
 
-    // HACK(eddyb) replace this with having `Option` around `&TypeckTables`.
-    pub(super) empty_typeck_tables: &'a ty::TypeckTables<'tcx>,
-
     /// Parameter environment for the item we are in.
     pub param_env: ty::ParamEnv<'tcx>,
 
@@ -677,18 +675,35 @@ impl LintContext for EarlyContext<'_> {
 
 impl<'a, 'tcx> LateContext<'a, 'tcx> {
     /// Gets the type-checking side-tables for the current body,
-    /// or empty `TypeckTables` if outside a body.
-    // FIXME(eddyb) return `Option<&'tcx ty::TypeckTables<'tcx>>`,
-    // where `None` indicates we're outside a body.
-    pub fn tables(&self) -> &'a ty::TypeckTables<'tcx> {
-        if let Some(body) = self.enclosing_body {
-            self.cached_typeck_tables.get().unwrap_or_else(|| {
+    /// or `None` if outside a body.
+    pub fn maybe_typeck_tables(&self) -> Option<&'tcx ty::TypeckTables<'tcx>> {
+        self.cached_typeck_tables.get().or_else(|| {
+            self.enclosing_body.map(|body| {
                 let tables = self.tcx.body_tables(body);
                 self.cached_typeck_tables.set(Some(tables));
                 tables
             })
-        } else {
-            self.empty_typeck_tables
+        })
+    }
+
+    /// Gets the type-checking side-tables for the current body.
+    /// As this will ICE if called outside bodies, only call when working with
+    /// `Expr` or `Pat` nodes (they are guaranteed to be found only in bodies).
+    #[track_caller]
+    pub fn tables(&self) -> &'tcx ty::TypeckTables<'tcx> {
+        self.maybe_typeck_tables().expect("`LateContext::tables` called outside of body")
+    }
+
+    /// Returns the final resolution of a `QPath`, or `Res::Err` if unavailable.
+    /// Unlike `.tables().qpath_res(qpath, id)`, this can be used even outside
+    /// bodies (e.g. for paths in `hir::Ty`), without any risk of ICE-ing.
+    pub fn qpath_res(&self, qpath: &hir::QPath<'_>, id: hir::HirId) -> Res {
+        match *qpath {
+            hir::QPath::Resolved(_, ref path) => path.res,
+            hir::QPath::TypeRelative(..) => self
+                .maybe_typeck_tables()
+                .and_then(|tables| tables.type_dependent_def(id))
+                .map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
         }
     }
 

src/librustc_lint/late.rs

@@ -378,7 +378,6 @@ fn late_lint_mod_pass<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(
         tcx,
         enclosing_body: None,
         cached_typeck_tables: Cell::new(None),
-        empty_typeck_tables: &ty::TypeckTables::empty(None),
         param_env: ty::ParamEnv::empty(),
         access_levels,
         lint_store: unerased_lint_store(tcx),
@@ -427,7 +426,6 @@ fn late_lint_pass_crate<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(tcx: TyCtxt<'tc
         tcx,
         enclosing_body: None,
         cached_typeck_tables: Cell::new(None),
-        empty_typeck_tables: &ty::TypeckTables::empty(None),
         param_env: ty::ParamEnv::empty(),
         access_levels,
         lint_store: unerased_lint_store(tcx),

src/librustc_lint/lib.rs

@@ -34,6 +34,7 @@
 #![feature(never_type)]
 #![feature(nll)]
 #![feature(or_patterns)]
+#![cfg_attr(bootstrap, feature(track_caller))]
 #![recursion_limit = "256"]
 
 #[macro_use]

src/librustc_lint/unused.rs

@@ -55,7 +55,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults {
             hir::ExprKind::Call(ref callee, _) => {
                 match callee.kind {
                     hir::ExprKind::Path(ref qpath) => {
-                        match cx.tables().qpath_res(qpath, callee.hir_id) {
+                        match cx.qpath_res(qpath, callee.hir_id) {
                             Res::Def(DefKind::Fn | DefKind::AssocFn, def_id) => Some(def_id),
                             // `Res::Local` if it was a closure, for which we
                             // do not currently support must-use linting