Auto merge of #50929 - zackmdavis:hiridification_initiative, r=michaelwoerister

operate on `HirId` instead of `NodeId` in `hir::Pat::each_binding`, and consequences of that

See #50928 for motivation.

Questions—

 * Is #50928 actually a good idea as a plan of record, or is there some reason to keep `NodeId`s?
 * Are the uses of `find_node_for_hir_id` in this initial submission OK (see the FIXME comments)?
 * Can we bikeshed a better method names `struct_span_lint_hir` _&c._? (Coined in analogy to the `struct_span_lint_node` and `NodeId`, but it feels kind of semantically clunky.)

r? @michaelwoerister

Author: bors

src/librustc/hir/map/definitions.rs

@@ -487,14 +487,6 @@ impl Definitions {
         self.node_to_hir_id[node_id]
     }
 
-    pub fn find_node_for_hir_id(&self, hir_id: hir::HirId) -> ast::NodeId {
-        self.node_to_hir_id
-            .iter()
-            .position(|x| *x == hir_id)
-            .map(|idx| ast::NodeId::new(idx))
-            .unwrap()
-    }
-
     #[inline]
     pub fn def_index_to_hir_id(&self, def_index: DefIndex) -> hir::HirId {
         let space_index = def_index.address_space().index();

src/librustc/hir/pat_util.rs

@@ -10,7 +10,7 @@
 
 use hir::def::Def;
 use hir::def_id::DefId;
-use hir::{self, PatKind};
+use hir::{self, HirId, PatKind};
 use syntax::ast;
 use syntax::codemap::Spanned;
 use syntax_pos::Span;
@@ -91,11 +91,11 @@ impl hir::Pat {
     /// Call `f` on every "binding" in a pattern, e.g., on `a` in
     /// `match foo() { Some(a) => (), None => () }`
     pub fn each_binding<F>(&self, mut f: F)
-        where F: FnMut(hir::BindingAnnotation, ast::NodeId, Span, &Spanned<ast::Name>),
+        where F: FnMut(hir::BindingAnnotation, HirId, Span, &Spanned<ast::Name>),
     {
         self.walk(|p| {
             if let PatKind::Binding(binding_mode, _, ref pth, _) = p.node {
-                f(binding_mode, p.id, p.span, pth);
+                f(binding_mode, p.hir_id, p.span, pth);
             }
             true
         });

src/librustc/middle/expr_use_visitor.rs

@@ -608,9 +608,9 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
     fn walk_local(&mut self, local: &hir::Local) {
         match local.init {
             None => {
-                let delegate = &mut self.delegate;
-                local.pat.each_binding(|_, id, span, _| {
-                    delegate.decl_without_init(id, span);
+                local.pat.each_binding(|_, hir_id, span, _| {
+                    let node_id = self.mc.tcx.hir.hir_to_node_id(hir_id);
+                    self.delegate.decl_without_init(node_id, span);
                 })
             }