Rollup merge of #40315 - oli-obk:lint_body, r=eddyb

Allow lints to check Bodys directly

r? @eddyb

babysteps towards fixing https://github.com/Manishearth/rust-clippy/issues/1580 (disable certain lints in const environments, since they make no sense there (yet))

src/librustc/lint/context.rs

@@ -806,6 +806,12 @@ fn visit_nested_body(&mut self, body: hir::BodyId) {
         self.tables = old_tables;
     }
 
+    fn visit_body(&mut self, body: &'tcx hir::Body) {
+        run_lints!(self, check_body, late_passes, body);
+        hir_visit::walk_body(self, body);
+        run_lints!(self, check_body_post, late_passes, body);
+    }
+
     fn visit_item(&mut self, it: &'tcx hir::Item) {
         self.with_lint_attrs(&it.attrs, |cx| {
             run_lints!(cx, check_item, late_passes, it);

src/librustc/lint/mod.rs

@@ -133,6 +133,8 @@ pub trait LintPass {
 // FIXME: eliminate the duplication with `Visitor`. But this also
 // contains a few lint-specific methods with no equivalent in `Visitor`.
 pub trait LateLintPass<'a, 'tcx>: LintPass {
+    fn check_body(&mut self, _: &LateContext, _: &'tcx hir::Body) { }
+    fn check_body_post(&mut self, _: &LateContext, _: &'tcx hir::Body) { }
     fn check_name(&mut self, _: &LateContext, _: Span, _: ast::Name) { }
     fn check_crate(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Crate) { }
     fn check_crate_post(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Crate) { }