Auto merge of #38449 - eddyb:lazy-10, r=nikomatsakis

[10/n] Split constants and functions' arguments into disjoint bodies.

_This is part of a series ([prev](#38053) | [next]()) of patches designed to rework rustc into an out-of-order on-demand pipeline model for both better feature support (e.g. [MIR-based](https://github.com/solson/miri) early constant evaluation) and incremental execution of compiler passes (e.g. type-checking), with beneficial consequences to IDE support as well.
If any motivation is unclear, please ask for additional PR description clarifications or code comments._

<hr>

Finishes the signature-body split started in #37918, namely:
* `trait` items are separated just like `impl` items were, for uniformity, closing #37712
* `static`s, `const`s (including associated ones), `enum` discriminants and array lengths get bodies
  * even the count in "repeat expressions", i.e. `n` in `[x; n]`, which fixes #24414
* arguments' patterns are moved to the bodies, with the types staying in `FnDecl`
  * `&self` now desugars to `self: &Self` instead of `self: &_` (similarly for other `self` forms)
  * `astconv`'s and metadata's (for rustdoc) informative uses are explicitly ignored for the purposes of the dep graph. this could be fixed in the future by hashing the exact information being extracted about the arguments as opposed to generating a dependency on *the whole body*

src/librustc/cfg/construct.rs

@@ -327,10 +327,6 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                 self.opt_expr(base, field_cfg)
             }
 
-            hir::ExprRepeat(ref elem, ref count) => {
-                self.straightline(expr, pred, [elem, count].iter().map(|&e| &**e))
-            }
-
             hir::ExprAssign(ref l, ref r) |
             hir::ExprAssignOp(_, ref l, ref r) => {
                 self.straightline(expr, pred, [r, l].iter().map(|&e| &**e))
@@ -347,7 +343,8 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
             hir::ExprType(ref e, _) |
             hir::ExprUnary(_, ref e) |
             hir::ExprField(ref e, _) |
-            hir::ExprTupField(ref e, _) => {
+            hir::ExprTupField(ref e, _) |
+            hir::ExprRepeat(ref e, _) => {
                 self.straightline(expr, pred, Some(&**e).into_iter())
             }
 

src/librustc/dep_graph/graph.rs

@@ -51,6 +51,12 @@ impl DepGraph {
         }
     }
 
+    /// True if we are actually building the full dep-graph.
+    #[inline]
+    pub fn is_fully_enabled(&self) -> bool {
+        self.data.thread.is_fully_enabled()
+    }
+
     pub fn query(&self) -> DepGraphQuery<DefId> {
         self.data.thread.query()
     }

src/librustc/dep_graph/visit.rs

@@ -45,6 +45,16 @@ pub fn visit_all_item_likes_in_krate<'a, 'tcx, V, F>(tcx: TyCtxt<'a, 'tcx, 'tcx>
             debug!("Ended task {:?}", task_id);
         }
 
+        fn visit_trait_item(&mut self, i: &'tcx hir::TraitItem) {
+            let trait_item_def_id = self.tcx.map.local_def_id(i.id);
+            let task_id = (self.dep_node_fn)(trait_item_def_id);
+            let _task = self.tcx.dep_graph.in_task(task_id.clone());
+            debug!("Started task {:?}", task_id);
+            self.tcx.dep_graph.read(DepNode::Hir(trait_item_def_id));
+            self.visitor.visit_trait_item(i);
+            debug!("Ended task {:?}", task_id);
+        }
+
         fn visit_impl_item(&mut self, i: &'tcx hir::ImplItem) {
             let impl_item_def_id = self.tcx.map.local_def_id(i.id);
             let task_id = (self.dep_node_fn)(impl_item_def_id);

src/librustc/hir/intravisit.rs

@@ -177,6 +177,17 @@ pub trait Visitor<'v> : Sized {
         }
     }
 
+    /// Like `visit_nested_item()`, but for trait items. See
+    /// `visit_nested_item()` for advice on when to override this
+    /// method.
+    #[allow(unused_variables)]
+    fn visit_nested_trait_item(&mut self, id: TraitItemId) {
+        let opt_item = self.nested_visit_map().inter().map(|map| map.trait_item(id));
+        if let Some(item) = opt_item {
+            self.visit_trait_item(item);
+        }
+    }
+
     /// Like `visit_nested_item()`, but for impl items. See
     /// `visit_nested_item()` for advice on when to override this
     /// method.
@@ -192,10 +203,10 @@ pub trait Visitor<'v> : Sized {
     /// visit_nested_item, does nothing by default unless you override
     /// `nested_visit_map` to return `Some(_)`, in which case it will walk the
     /// body.
-    fn visit_body(&mut self, id: ExprId) {
-        let opt_expr = self.nested_visit_map().intra().map(|map| map.expr(id));
-        if let Some(expr) = opt_expr {
-            self.visit_expr(expr);
+    fn visit_nested_body(&mut self, id: BodyId) {
+        let opt_body = self.nested_visit_map().intra().map(|map| map.body(id));
+        if let Some(body) = opt_body {
+            self.visit_body(body);
         }
     }
 
@@ -205,6 +216,10 @@ pub trait Visitor<'v> : Sized {
         walk_item(self, i)
     }
 
+    fn visit_body(&mut self, b: &'v Body) {
+        walk_body(self, b);
+    }
+
     /// When invoking `visit_all_item_likes()`, you need to supply an
     /// item-like visitor.  This method converts a "intra-visit"
     /// visitor into an item-like visitor that walks the entire tree.
@@ -253,8 +268,6 @@ pub trait Visitor<'v> : Sized {
     fn visit_expr(&mut self, ex: &'v Expr) {
         walk_expr(self, ex)
     }
-    fn visit_expr_post(&mut self, _ex: &'v Expr) {
-    }
     fn visit_ty(&mut self, t: &'v Ty) {
         walk_ty(self, t)
     }
@@ -267,12 +280,15 @@ pub trait Visitor<'v> : Sized {
     fn visit_fn_decl(&mut self, fd: &'v FnDecl) {
         walk_fn_decl(self, fd)
     }
-    fn visit_fn(&mut self, fk: FnKind<'v>, fd: &'v FnDecl, b: ExprId, s: Span, id: NodeId) {
+    fn visit_fn(&mut self, fk: FnKind<'v>, fd: &'v FnDecl, b: BodyId, s: Span, id: NodeId) {
         walk_fn(self, fk, fd, b, s, id)
     }
     fn visit_trait_item(&mut self, ti: &'v TraitItem) {
         walk_trait_item(self, ti)
     }
+    fn visit_trait_item_ref(&mut self, ii: &'v TraitItemRef) {
+        walk_trait_item_ref(self, ii)
+    }
     fn visit_impl_item(&mut self, ii: &'v ImplItem) {
         walk_impl_item(self, ii)
     }
@@ -378,6 +394,14 @@ pub fn walk_mod<'v, V: Visitor<'v>>(visitor: &mut V, module: &'v Mod, mod_node_i
     }
 }
 
+pub fn walk_body<'v, V: Visitor<'v>>(visitor: &mut V, body: &'v Body) {
+    for argument in &body.arguments {
+        visitor.visit_id(argument.id);
+        visitor.visit_pat(&argument.pat);
+    }
+    visitor.visit_expr(&body.value);
+}
+
 pub fn walk_local<'v, V: Visitor<'v>>(visitor: &mut V, local: &'v Local) {
     visitor.visit_id(local.id);
     visitor.visit_pat(&local.pat);
@@ -423,11 +447,11 @@ pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item) {
             visitor.visit_id(item.id);
             visitor.visit_path(path, item.id);
         }
-        ItemStatic(ref typ, _, ref expr) |
-        ItemConst(ref typ, ref expr) => {
+        ItemStatic(ref typ, _, body) |
+        ItemConst(ref typ, body) => {
             visitor.visit_id(item.id);
             visitor.visit_ty(typ);
-            visitor.visit_expr(expr);
+            visitor.visit_nested_body(body);
         }
         ItemFn(ref declaration, unsafety, constness, abi, ref generics, body_id) => {
             visitor.visit_fn(FnKind::ItemFn(item.name,
@@ -469,21 +493,19 @@ pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item) {
             visitor.visit_generics(type_parameters);
             walk_list!(visitor, visit_trait_ref, opt_trait_reference);
             visitor.visit_ty(typ);
-            for impl_item_ref in impl_item_refs {
-                visitor.visit_impl_item_ref(impl_item_ref);
-            }
+            walk_list!(visitor, visit_impl_item_ref, impl_item_refs);
         }
         ItemStruct(ref struct_definition, ref generics) |
         ItemUnion(ref struct_definition, ref generics) => {
             visitor.visit_generics(generics);
             visitor.visit_id(item.id);
             visitor.visit_variant_data(struct_definition, item.name, generics, item.id, item.span);
         }
-        ItemTrait(_, ref generics, ref bounds, ref methods) => {
+        ItemTrait(_, ref generics, ref bounds, ref trait_item_refs) => {
             visitor.visit_id(item.id);
             visitor.visit_generics(generics);
             walk_list!(visitor, visit_ty_param_bound, bounds);
-            walk_list!(visitor, visit_trait_item, methods);
+            walk_list!(visitor, visit_trait_item_ref, trait_item_refs);
         }
     }
     walk_list!(visitor, visit_attribute, &item.attrs);
@@ -511,7 +533,7 @@ pub fn walk_variant<'v, V: Visitor<'v>>(visitor: &mut V,
                                generics,
                                parent_item_id,
                                variant.span);
-    walk_list!(visitor, visit_expr, &variant.node.disr_expr);
+    walk_list!(visitor, visit_nested_body, variant.node.disr_expr);
     walk_list!(visitor, visit_attribute, &variant.node.attrs);
 }
 
@@ -544,18 +566,18 @@ pub fn walk_ty<'v, V: Visitor<'v>>(visitor: &mut V, typ: &'v Ty) {
             visitor.visit_ty(ty);
             walk_list!(visitor, visit_ty_param_bound, bounds);
         }
-        TyArray(ref ty, ref expression) => {
+        TyArray(ref ty, length) => {
             visitor.visit_ty(ty);
-            visitor.visit_expr(expression)
+            visitor.visit_nested_body(length)
         }
         TyPolyTraitRef(ref bounds) => {
             walk_list!(visitor, visit_ty_param_bound, bounds);
         }
         TyImplTrait(ref bounds) => {
             walk_list!(visitor, visit_ty_param_bound, bounds);
         }
-        TyTypeof(ref expression) => {
-            visitor.visit_expr(expression)
+        TyTypeof(expression) => {
+            visitor.visit_nested_body(expression)
         }
         TyInfer => {}
     }
@@ -662,9 +684,12 @@ pub fn walk_foreign_item<'v, V: Visitor<'v>>(visitor: &mut V, foreign_item: &'v
     visitor.visit_name(foreign_item.span, foreign_item.name);
 
     match foreign_item.node {
-        ForeignItemFn(ref function_declaration, ref generics) => {
+        ForeignItemFn(ref function_declaration, ref names, ref generics) => {
+            visitor.visit_generics(generics);
             visitor.visit_fn_decl(function_declaration);
-            visitor.visit_generics(generics)
+            for name in names {
+                visitor.visit_name(name.span, name.node);
+            }
         }
         ForeignItemStatic(ref typ, _) => visitor.visit_ty(typ),
     }
@@ -732,18 +757,8 @@ pub fn walk_fn_ret_ty<'v, V: Visitor<'v>>(visitor: &mut V, ret_ty: &'v FunctionR
 }
 
 pub fn walk_fn_decl<'v, V: Visitor<'v>>(visitor: &mut V, function_declaration: &'v FnDecl) {
-    for argument in &function_declaration.inputs {
-        visitor.visit_id(argument.id);
-        visitor.visit_pat(&argument.pat);
-        visitor.visit_ty(&argument.ty)
-    }
-    walk_fn_ret_ty(visitor, &function_declaration.output)
-}
-
-pub fn walk_fn_decl_nopat<'v, V: Visitor<'v>>(visitor: &mut V, function_declaration: &'v FnDecl) {
-    for argument in &function_declaration.inputs {
-        visitor.visit_id(argument.id);
-        visitor.visit_ty(&argument.ty)
+    for ty in &function_declaration.inputs {
+        visitor.visit_ty(ty)
     }
     walk_fn_ret_ty(visitor, &function_declaration.output)
 }
@@ -763,42 +778,33 @@ pub fn walk_fn_kind<'v, V: Visitor<'v>>(visitor: &mut V, function_kind: FnKind<'
 pub fn walk_fn<'v, V: Visitor<'v>>(visitor: &mut V,
                                    function_kind: FnKind<'v>,
                                    function_declaration: &'v FnDecl,
-                                   body_id: ExprId,
+                                   body_id: BodyId,
                                    _span: Span,
                                    id: NodeId) {
     visitor.visit_id(id);
     visitor.visit_fn_decl(function_declaration);
     walk_fn_kind(visitor, function_kind);
-    visitor.visit_body(body_id)
-}
-
-pub fn walk_fn_with_body<'v, V: Visitor<'v>>(visitor: &mut V,
-                                             function_kind: FnKind<'v>,
-                                             function_declaration: &'v FnDecl,
-                                             body: &'v Expr,
-                                             _span: Span,
-                                             id: NodeId) {
-    visitor.visit_id(id);
-    visitor.visit_fn_decl(function_declaration);
-    walk_fn_kind(visitor, function_kind);
-    visitor.visit_expr(body)
+    visitor.visit_nested_body(body_id)
 }
 
 pub fn walk_trait_item<'v, V: Visitor<'v>>(visitor: &mut V, trait_item: &'v TraitItem) {
     visitor.visit_name(trait_item.span, trait_item.name);
     walk_list!(visitor, visit_attribute, &trait_item.attrs);
     match trait_item.node {
-        ConstTraitItem(ref ty, ref default) => {
+        TraitItemKind::Const(ref ty, default) => {
             visitor.visit_id(trait_item.id);
             visitor.visit_ty(ty);
-            walk_list!(visitor, visit_expr, default);
+            walk_list!(visitor, visit_nested_body, default);
         }
-        MethodTraitItem(ref sig, None) => {
+        TraitItemKind::Method(ref sig, TraitMethod::Required(ref names)) => {
             visitor.visit_id(trait_item.id);
             visitor.visit_generics(&sig.generics);
             visitor.visit_fn_decl(&sig.decl);
+            for name in names {
+                visitor.visit_name(name.span, name.node);
+            }
         }
-        MethodTraitItem(ref sig, Some(body_id)) => {
+        TraitItemKind::Method(ref sig, TraitMethod::Provided(body_id)) => {
             visitor.visit_fn(FnKind::Method(trait_item.name,
                                             sig,
                                             None,
@@ -808,14 +814,23 @@ pub fn walk_trait_item<'v, V: Visitor<'v>>(visitor: &mut V, trait_item: &'v Trai
                              trait_item.span,
                              trait_item.id);
         }
-        TypeTraitItem(ref bounds, ref default) => {
+        TraitItemKind::Type(ref bounds, ref default) => {
             visitor.visit_id(trait_item.id);
             walk_list!(visitor, visit_ty_param_bound, bounds);
             walk_list!(visitor, visit_ty, default);
         }
     }
 }
 
+pub fn walk_trait_item_ref<'v, V: Visitor<'v>>(visitor: &mut V, trait_item_ref: &'v TraitItemRef) {
+    // NB: Deliberately force a compilation error if/when new fields are added.
+    let TraitItemRef { id, name, ref kind, span, ref defaultness } = *trait_item_ref;
+    visitor.visit_nested_trait_item(id);
+    visitor.visit_name(span, name);
+    visitor.visit_associated_item_kind(kind);
+    visitor.visit_defaultness(defaultness);
+}
+
 pub fn walk_impl_item<'v, V: Visitor<'v>>(visitor: &mut V, impl_item: &'v ImplItem) {
     // NB: Deliberately force a compilation error if/when new fields are added.
     let ImplItem { id: _, name, ref vis, ref defaultness, ref attrs, ref node, span } = *impl_item;
@@ -825,10 +840,10 @@ pub fn walk_impl_item<'v, V: Visitor<'v>>(visitor: &mut V, impl_item: &'v ImplIt
     visitor.visit_defaultness(defaultness);
     walk_list!(visitor, visit_attribute, attrs);
     match *node {
-        ImplItemKind::Const(ref ty, ref expr) => {
+        ImplItemKind::Const(ref ty, body) => {
             visitor.visit_id(impl_item.id);
             visitor.visit_ty(ty);
-            visitor.visit_expr(expr);
+            visitor.visit_nested_body(body);
         }
         ImplItemKind::Method(ref sig, body_id) => {
             visitor.visit_fn(FnKind::Method(impl_item.name,
@@ -907,9 +922,9 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr) {
         ExprArray(ref subexpressions) => {
             walk_list!(visitor, visit_expr, subexpressions);
         }
-        ExprRepeat(ref element, ref count) => {
+        ExprRepeat(ref element, count) => {
             visitor.visit_expr(element);
-            visitor.visit_expr(count)
+            visitor.visit_nested_body(count)
         }
         ExprStruct(ref qpath, ref fields, ref optional_base) => {
             visitor.visit_qpath(qpath, expression.id, expression.span);
@@ -1016,8 +1031,6 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr) {
             }
         }
     }
-
-    visitor.visit_expr_post(expression)
 }
 
 pub fn walk_arm<'v, V: Visitor<'v>>(visitor: &mut V, arm: &'v Arm) {
@@ -1100,16 +1113,3 @@ impl<'a, 'ast> Visitor<'ast> for IdRangeComputingVisitor<'a, 'ast> {
         self.result.add(id);
     }
 }
-
-/// Computes the id range for a single fn body, ignoring nested items.
-pub fn compute_id_range_for_fn_body<'v>(fk: FnKind<'v>,
-                                        decl: &'v FnDecl,
-                                        body: &'v Expr,
-                                        sp: Span,
-                                        id: NodeId,
-                                        map: &map::Map<'v>)
-                                        -> IdRange {
-    let mut visitor = IdRangeComputingVisitor::new(map);
-    walk_fn_with_body(&mut visitor, fk, decl, body, sp, id);
-    visitor.result()
-}

src/librustc/hir/itemlikevisit.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use super::{Item, ImplItem};
+use super::{Item, ImplItem, TraitItem};
 use super::intravisit::Visitor;
 
 /// The "item-like visitor" visitor defines only the top-level methods
@@ -58,6 +58,7 @@ use super::intravisit::Visitor;
 /// needed.
 pub trait ItemLikeVisitor<'hir> {
     fn visit_item(&mut self, item: &'hir Item);
+    fn visit_trait_item(&mut self, trait_item: &'hir TraitItem);
     fn visit_impl_item(&mut self, impl_item: &'hir ImplItem);
 }
 
@@ -80,6 +81,10 @@ impl<'v, 'hir, V> ItemLikeVisitor<'hir> for DeepVisitor<'v, V>
         self.visitor.visit_item(item);
     }
 
+    fn visit_trait_item(&mut self, trait_item: &'hir TraitItem) {
+        self.visitor.visit_trait_item(trait_item);
+    }
+
     fn visit_impl_item(&mut self, impl_item: &'hir ImplItem) {
         self.visitor.visit_impl_item(impl_item);
     }