Use FnvHashMap in more places

* A step towards #34902
* More stable error messages in some places related to crate loading
* Possible slight performance improvements since all `HashMap`s
  replaced had small keys where `FnvHashMap` should be faster
  (although I didn't measure)

src/librustc/infer/freshen.rs

@@ -32,15 +32,16 @@
 
 use ty::{self, Ty, TyCtxt, TypeFoldable};
 use ty::fold::TypeFolder;
-use std::collections::hash_map::{self, Entry};
+use util::nodemap::FnvHashMap;
+use std::collections::hash_map::Entry;
 
 use super::InferCtxt;
 use super::unify_key::ToType;
 
 pub struct TypeFreshener<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
     freshen_count: u32,
-    freshen_map: hash_map::HashMap<ty::InferTy, Ty<'tcx>>,
+    freshen_map: FnvHashMap<ty::InferTy, Ty<'tcx>>,
 }
 
 impl<'a, 'gcx, 'tcx> TypeFreshener<'a, 'gcx, 'tcx> {
@@ -49,7 +50,7 @@ impl<'a, 'gcx, 'tcx> TypeFreshener<'a, 'gcx, 'tcx> {
         TypeFreshener {
             infcx: infcx,
             freshen_count: 0,
-            freshen_map: hash_map::HashMap::new(),
+            freshen_map: FnvHashMap(),
         }
     }
 

src/librustc/middle/dead.rs

@@ -22,8 +22,8 @@ use ty::{self, TyCtxt};
 use hir::def::Def;
 use hir::def_id::{DefId};
 use lint;
+use util::nodemap::FnvHashSet;
 
-use std::collections::HashSet;
 use syntax::{ast, codemap};
 use syntax::attr;
 use syntax_pos;
@@ -48,7 +48,7 @@ fn should_explore<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 struct MarkSymbolVisitor<'a, 'tcx: 'a> {
     worklist: Vec<ast::NodeId>,
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
-    live_symbols: Box<HashSet<ast::NodeId>>,
+    live_symbols: Box<FnvHashSet<ast::NodeId>>,
     struct_has_extern_repr: bool,
     ignore_non_const_paths: bool,
     inherited_pub_visibility: bool,
@@ -61,7 +61,7 @@ impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
         MarkSymbolVisitor {
             worklist: worklist,
             tcx: tcx,
-            live_symbols: box HashSet::new(),
+            live_symbols: box FnvHashSet(),
             struct_has_extern_repr: false,
             ignore_non_const_paths: false,
             inherited_pub_visibility: false,
@@ -162,7 +162,7 @@ impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
     }
 
     fn mark_live_symbols(&mut self) {
-        let mut scanned = HashSet::new();
+        let mut scanned = FnvHashSet();
         while !self.worklist.is_empty() {
             let id = self.worklist.pop().unwrap();
             if scanned.contains(&id) {
@@ -395,7 +395,7 @@ fn create_and_seed_worklist<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 fn find_live<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                        access_levels: &privacy::AccessLevels,
                        krate: &hir::Crate)
-                       -> Box<HashSet<ast::NodeId>> {
+                       -> Box<FnvHashSet<ast::NodeId>> {
     let worklist = create_and_seed_worklist(tcx, access_levels, krate);
     let mut symbol_visitor = MarkSymbolVisitor::new(tcx, worklist);
     symbol_visitor.mark_live_symbols();
@@ -413,7 +413,7 @@ fn get_struct_ctor_id(item: &hir::Item) -> Option<ast::NodeId> {
 
 struct DeadVisitor<'a, 'tcx: 'a> {
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
-    live_symbols: Box<HashSet<ast::NodeId>>,
+    live_symbols: Box<FnvHashSet<ast::NodeId>>,
 }
 
 impl<'a, 'tcx> DeadVisitor<'a, 'tcx> {

src/librustc/middle/reachable.rs

@@ -22,9 +22,8 @@ use hir::def_id::DefId;
 use ty::{self, TyCtxt};
 use middle::privacy;
 use session::config;
-use util::nodemap::NodeSet;
+use util::nodemap::{NodeSet, FnvHashSet};
 
-use std::collections::HashSet;
 use syntax::abi::Abi;
 use syntax::ast;
 use syntax::attr;
@@ -204,7 +203,7 @@ impl<'a, 'tcx> ReachableContext<'a, 'tcx> {
 
     // Step 2: Mark all symbols that the symbols on the worklist touch.
     fn propagate(&mut self) {
-        let mut scanned = HashSet::new();
+        let mut scanned = FnvHashSet();
         loop {
             let search_item = match self.worklist.pop() {
                 Some(item) => item,

src/librustc_metadata/loader.rs

@@ -221,6 +221,7 @@ use rustc::session::Session;
 use rustc::session::filesearch::{FileSearch, FileMatches, FileDoesntMatch};
 use rustc::session::search_paths::PathKind;
 use rustc::util::common;
+use rustc::util::nodemap::FnvHashMap;
 
 use rustc_llvm as llvm;
 use rustc_llvm::{False, ObjectFile, mk_section_iter};
@@ -230,7 +231,6 @@ use syntax_pos::Span;
 use rustc_back::target::Target;
 
 use std::cmp;
-use std::collections::HashMap;
 use std::fmt;
 use std::fs;
 use std::io;
@@ -413,7 +413,7 @@ impl<'a> Context<'a> {
         let rlib_prefix = format!("lib{}", self.crate_name);
         let staticlib_prefix = format!("{}{}", staticpair.0, self.crate_name);
 
-        let mut candidates = HashMap::new();
+        let mut candidates = FnvHashMap();
         let mut staticlibs = vec!();
 
         // First, find all possible candidate rlibs and dylibs purely based on
@@ -456,7 +456,7 @@ impl<'a> Context<'a> {
 
             let hash_str = hash.to_string();
             let slot = candidates.entry(hash_str)
-                                 .or_insert_with(|| (HashMap::new(), HashMap::new()));
+                                 .or_insert_with(|| (FnvHashMap(), FnvHashMap()));
             let (ref mut rlibs, ref mut dylibs) = *slot;
             fs::canonicalize(path).map(|p| {
                 if rlib {
@@ -477,7 +477,7 @@ impl<'a> Context<'a> {
         // A Library candidate is created if the metadata for the set of
         // libraries corresponds to the crate id and hash criteria that this
         // search is being performed for.
-        let mut libraries = HashMap::new();
+        let mut libraries = FnvHashMap();
         for (_hash, (rlibs, dylibs)) in candidates {
             let mut slot = None;
             let rlib = self.extract_one(rlibs, CrateFlavor::Rlib, &mut slot);
@@ -527,7 +527,7 @@ impl<'a> Context<'a> {
     // read the metadata from it if `*slot` is `None`. If the metadata couldn't
     // be read, it is assumed that the file isn't a valid rust library (no
     // errors are emitted).
-    fn extract_one(&mut self, m: HashMap<PathBuf, PathKind>, flavor: CrateFlavor,
+    fn extract_one(&mut self, m: FnvHashMap<PathBuf, PathKind>, flavor: CrateFlavor,
                    slot: &mut Option<(Svh, MetadataBlob)>) -> Option<(PathBuf, PathKind)> {
         let mut ret: Option<(PathBuf, PathKind)> = None;
         let mut error = 0;
@@ -669,8 +669,8 @@ impl<'a> Context<'a> {
         // rlibs/dylibs.
         let sess = self.sess;
         let dylibname = self.dylibname();
-        let mut rlibs = HashMap::new();
-        let mut dylibs = HashMap::new();
+        let mut rlibs = FnvHashMap();
+        let mut dylibs = FnvHashMap();
         {
             let locs = locs.map(|l| PathBuf::from(l)).filter(|loc| {
                 if !loc.exists() {

src/librustc_metadata/macro_import.rs

@@ -14,8 +14,8 @@ use creader::CrateReader;
 use cstore::CStore;
 
 use rustc::session::Session;
+use rustc::util::nodemap::{FnvHashSet, FnvHashMap};
 
-use std::collections::{HashSet, HashMap};
 use syntax::parse::token;
 use syntax::ast;
 use syntax::attr;
@@ -45,13 +45,13 @@ pub fn call_bad_macro_reexport(a: &Session, b: Span) {
     span_err!(a, b, E0467, "bad macro reexport");
 }
 
-pub type MacroSelection = HashMap<token::InternedString, Span>;
+pub type MacroSelection = FnvHashMap<token::InternedString, Span>;
 
 impl<'a> ext::base::MacroLoader for MacroLoader<'a> {
     fn load_crate(&mut self, extern_crate: &ast::Item, allows_macros: bool) -> Vec<ast::MacroDef> {
         // Parse the attributes relating to macros.
-        let mut import = Some(HashMap::new());  // None => load all
-        let mut reexport = HashMap::new();
+        let mut import = Some(FnvHashMap());  // None => load all
+        let mut reexport = FnvHashMap();
 
         for attr in &extern_crate.attrs {
             let mut used = true;
@@ -120,7 +120,7 @@ impl<'a> MacroLoader<'a> {
         }
 
         let mut macros = Vec::new();
-        let mut seen = HashSet::new();
+        let mut seen = FnvHashSet();
 
         for mut def in self.reader.read_exported_macros(vi) {
             let name = def.ident.name.as_str();

src/librustc_resolve/assign_ids.rs

@@ -10,14 +10,14 @@
 
 use Resolver;
 use rustc::session::Session;
+use rustc::util::nodemap::FnvHashMap;
 use syntax::ast;
 use syntax::ext::hygiene::Mark;
 use syntax::fold::{self, Folder};
 use syntax::ptr::P;
 use syntax::util::move_map::MoveMap;
 use syntax::util::small_vector::SmallVector;
 
-use std::collections::HashMap;
 use std::mem;
 
 impl<'a> Resolver<'a> {
@@ -31,7 +31,7 @@ impl<'a> Resolver<'a> {
 
 struct NodeIdAssigner<'a> {
     sess: &'a Session,
-    macros_at_scope: &'a mut HashMap<ast::NodeId, Vec<Mark>>,
+    macros_at_scope: &'a mut FnvHashMap<ast::NodeId, Vec<Mark>>,
 }
 
 impl<'a> Folder for NodeIdAssigner<'a> {