resolve: Optimize path resolution for rustdoc

petrochenkov · petrochenkov · commit 15a8b981e08b · 2022-03-25T02:03:54.000+03:00
Do not construct or pass unused data
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
@@ -71,7 +71,7 @@ use rustc_span::{Span, DUMMY_SP};
 use smallvec::{smallvec, SmallVec};
 use std::cell::{Cell, RefCell};
 use std::collections::BTreeSet;
-use std::{cmp, fmt, iter, mem, ptr};
+use std::{cmp, fmt, mem, ptr};
 use tracing::debug;
 
 use diagnostics::{extend_span_to_previous_binding, find_span_of_binding_until_next_binding};
@@ -3309,82 +3309,39 @@ impl<'a> Resolver<'a> {
         })
     }
 
-    /// Rustdoc uses this to resolve things in a recoverable way. `ResolutionError<'a>`
+    /// Rustdoc uses this to resolve doc link paths in a recoverable way. `PathResult<'a>`
     /// isn't something that can be returned because it can't be made to live that long,
     /// and also it's a private type. Fortunately rustdoc doesn't need to know the error,
     /// just that an error occurred.
-    // FIXME(Manishearth): intra-doc links won't get warned of epoch changes.
-    pub fn resolve_str_path_error(
+    pub fn resolve_rustdoc_path(
         &mut self,
-        span: Span,
         path_str: &str,
         ns: Namespace,
         module_id: DefId,
-    ) -> Result<(ast::Path, Res), ()> {
-        let path = if path_str.starts_with("::") {
-            ast::Path {
-                span,
-                segments: iter::once(Ident::with_dummy_span(kw::PathRoot))
-                    .chain(path_str.split("::").skip(1).map(Ident::from_str))
-                    .map(|i| self.new_ast_path_segment(i))
-                    .collect(),
-                tokens: None,
-            }
-        } else {
-            ast::Path {
-                span,
-                segments: path_str
-                    .split("::")
-                    .map(Ident::from_str)
-                    .map(|i| self.new_ast_path_segment(i))
-                    .collect(),
-                tokens: None,
-            }
-        };
-        let module = self.expect_module(module_id);
-        let parent_scope = &ParentScope::module(module, self);
-        let res = self.resolve_ast_path(&path, ns, parent_scope).map_err(|_| ())?;
-        Ok((path, res))
-    }
+    ) -> Option<Res> {
+        let mut segments =
+            Vec::from_iter(path_str.split("::").map(Ident::from_str).map(Segment::from_ident));
+        if path_str.starts_with("::") {
+            segments[0].ident.name = kw::PathRoot;
+        }
 
-    // Resolve a path passed from rustdoc or HIR lowering.
-    fn resolve_ast_path(
-        &mut self,
-        path: &ast::Path,
-        ns: Namespace,
-        parent_scope: &ParentScope<'a>,
-    ) -> Result<Res, (Span, ResolutionError<'a>)> {
+        let module = self.expect_module(module_id);
         match self.resolve_path(
-            &Segment::from_path(path),
+            &segments,
             Some(ns),
-            parent_scope,
-            path.span,
+            &ParentScope::module(module, self),
+            DUMMY_SP,
             CrateLint::No,
         ) {
-            PathResult::Module(ModuleOrUniformRoot::Module(module)) => Ok(module.res().unwrap()),
+            PathResult::Module(ModuleOrUniformRoot::Module(module)) => Some(module.res().unwrap()),
             PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
-                Ok(path_res.base_res())
+                Some(path_res.base_res())
             }
-            PathResult::NonModule(..) => Err((
-                path.span,
-                ResolutionError::FailedToResolve {
-                    label: String::from("type-relative paths are not supported in this context"),
-                    suggestion: None,
-                },
-            )),
+            PathResult::NonModule(..) | PathResult::Failed { .. } => None,
             PathResult::Module(..) | PathResult::Indeterminate => unreachable!(),
-            PathResult::Failed { span, label, suggestion, .. } => {
-                Err((span, ResolutionError::FailedToResolve { label, suggestion }))
-            }
         }
     }
 
-    fn new_ast_path_segment(&mut self, ident: Ident) -> ast::PathSegment {
-        let mut seg = ast::PathSegment::from_ident(ident);
-        seg.id = self.next_node_id();
-        seg
-    }
-
     // For rustdoc.
     pub fn graph_root(&self) -> Module<'a> {
         self.graph_root
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -487,12 +487,10 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
         module_id: DefId,
     ) -> Result<Res, ResolutionFailure<'a>> {
         self.cx.enter_resolver(|resolver| {
-            // NOTE: this needs 2 separate lookups because `resolve_str_path_error` doesn't take
+            // NOTE: this needs 2 separate lookups because `resolve_rustdoc_path` doesn't take
             // lexical scope into account (it ignores all macros not defined at the mod-level)
             debug!("resolving {} as a macro in the module {:?}", path_str, module_id);
-            if let Ok((_, res)) =
-                resolver.resolve_str_path_error(DUMMY_SP, path_str, MacroNS, module_id)
-            {
+            if let Some(res) = resolver.resolve_rustdoc_path(path_str, MacroNS, module_id) {
                 // don't resolve builtins like `#[derive]`
                 if let Ok(res) = res.try_into() {
                     return Ok(res);
@@ -540,10 +538,10 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
             })
     }
 
-    /// Convenience wrapper around `resolve_str_path_error`.
+    /// Convenience wrapper around `resolve_rustdoc_path`.
     ///
     /// This also handles resolving `true` and `false` as booleans.
-    /// NOTE: `resolve_str_path_error` knows only about paths, not about types.
+    /// NOTE: `resolve_rustdoc_path` knows only about paths, not about types.
     /// Associated items will never be resolved by this function.
     fn resolve_path(
         &self,
@@ -556,18 +554,14 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
             return res;
         }
 
-        let result = self.cx.enter_resolver(|resolver| {
-            resolver
-                .resolve_str_path_error(DUMMY_SP, path_str, ns, module_id)
-                .and_then(|(_, res)| res.try_into())
-        });
+        // Resolver doesn't know about true, false, and types that aren't paths (e.g. `()`).
+        let result = self
+            .cx
+            .enter_resolver(|resolver| resolver.resolve_rustdoc_path(path_str, ns, module_id))
+            .and_then(|res| res.try_into().ok())
+            .or_else(|| resolve_primitive(path_str, ns));
         debug!("{} resolved to {:?} in namespace {:?}", path_str, result, ns);
-        match result {
-            // resolver doesn't know about true, false, and types that aren't paths (e.g. `()`)
-            // manually as bool
-            Err(()) => resolve_primitive(path_str, ns),
-            Ok(res) => Some(res),
-        }
+        result
     }
 
     /// Resolves a string as a path within a particular namespace. Returns an
diff --git a/src/librustdoc/passes/collect_intra_doc_links/early.rs b/src/librustdoc/passes/collect_intra_doc_links/early.rs
@@ -13,7 +13,7 @@ use rustc_hir::TraitCandidate;
 use rustc_middle::ty::{DefIdTree, Visibility};
 use rustc_resolve::{ParentScope, Resolver};
 use rustc_session::config::Externs;
-use rustc_span::{Span, SyntaxContext, DUMMY_SP};
+use rustc_span::SyntaxContext;
 
 use std::collections::hash_map::Entry;
 use std::mem;
@@ -39,7 +39,7 @@ crate fn early_resolve_intra_doc_links(
 
     // Overridden `visit_item` below doesn't apply to the crate root,
     // so we have to visit its attributes and reexports separately.
-    loader.load_links_in_attrs(&krate.attrs, krate.spans.inner_span);
+    loader.load_links_in_attrs(&krate.attrs);
     loader.process_module_children_or_reexports(CRATE_DEF_ID.to_def_id());
     visit::walk_crate(&mut loader, krate);
     loader.add_foreign_traits_in_scope();
@@ -49,12 +49,7 @@ crate fn early_resolve_intra_doc_links(
     // DO NOT REMOVE THIS without first testing on the reproducer in
     // https://github.com/jyn514/objr/commit/edcee7b8124abf0e4c63873e8422ff81beb11ebb
     for (extern_name, _) in externs.iter().filter(|(_, entry)| entry.add_prelude) {
-        let _ = loader.resolver.resolve_str_path_error(
-            DUMMY_SP,
-            extern_name,
-            TypeNS,
-            CRATE_DEF_ID.to_def_id(),
-        );
+        loader.resolver.resolve_rustdoc_path(extern_name, TypeNS, CRATE_DEF_ID.to_def_id());
     }
 
     ResolverCaches {
@@ -151,7 +146,7 @@ impl IntraLinkCrateLoader<'_, '_> {
         }
     }
 
-    fn load_links_in_attrs(&mut self, attrs: &[ast::Attribute], span: Span) {
+    fn load_links_in_attrs(&mut self, attrs: &[ast::Attribute]) {
         // FIXME: this needs to consider reexport inlining.
         let attrs = clean::Attributes::from_ast(attrs, None);
         for (parent_module, doc) in attrs.collapsed_doc_value_by_module_level() {
@@ -165,7 +160,7 @@ impl IntraLinkCrateLoader<'_, '_> {
                 } else {
                     continue;
                 };
-                let _ = self.resolver.resolve_str_path_error(span, &path_str, TypeNS, module_id);
+                self.resolver.resolve_rustdoc_path(&path_str, TypeNS, module_id);
             }
         }
     }
@@ -201,7 +196,7 @@ impl Visitor<'_> for IntraLinkCrateLoader<'_, '_> {
             // loaded, even if the module itself has no doc comments.
             self.add_traits_in_parent_scope(self.current_mod.to_def_id());
 
-            self.load_links_in_attrs(&item.attrs, item.span);
+            self.load_links_in_attrs(&item.attrs);
             self.process_module_children_or_reexports(self.current_mod.to_def_id());
             visit::walk_item(self, item);
 
@@ -216,28 +211,28 @@ impl Visitor<'_> for IntraLinkCrateLoader<'_, '_> {
                 }
                 _ => {}
             }
-            self.load_links_in_attrs(&item.attrs, item.span);
+            self.load_links_in_attrs(&item.attrs);
             visit::walk_item(self, item);
         }
     }
 
     fn visit_assoc_item(&mut self, item: &ast::AssocItem, ctxt: AssocCtxt) {
-        self.load_links_in_attrs(&item.attrs, item.span);
+        self.load_links_in_attrs(&item.attrs);
         visit::walk_assoc_item(self, item, ctxt)
     }
 
     fn visit_foreign_item(&mut self, item: &ast::ForeignItem) {
-        self.load_links_in_attrs(&item.attrs, item.span);
+        self.load_links_in_attrs(&item.attrs);
         visit::walk_foreign_item(self, item)
     }
 
     fn visit_variant(&mut self, v: &ast::Variant) {
-        self.load_links_in_attrs(&v.attrs, v.span);
+        self.load_links_in_attrs(&v.attrs);
         visit::walk_variant(self, v)
     }
 
     fn visit_field_def(&mut self, field: &ast::FieldDef) {
-        self.load_links_in_attrs(&field.attrs, field.span);
+        self.load_links_in_attrs(&field.attrs);
         visit::walk_field_def(self, field)
     }
 
