Refactor `hir::lowering` API

src/librustc/hir/lowering.rs

@@ -91,30 +91,33 @@ impl Resolver for DummyResolver {
     }
 }
 
-impl<'a> LoweringContext<'a> {
-    pub fn new(id_assigner: &'a NodeIdAssigner,
-               c: Option<&Crate>,
-               resolver: &'a mut Resolver)
-               -> LoweringContext<'a> {
-        let crate_root = c.and_then(|c| {
-            if std_inject::no_core(c) {
-                None
-            } else if std_inject::no_std(c) {
-                Some("core")
-            } else {
-                Some("std")
-            }
-        });
+pub fn lower_crate(krate: &Crate, id_assigner: &NodeIdAssigner, resolver: &mut Resolver)
+                   -> hir::Crate {
+    LoweringContext {
+        crate_root: if std_inject::no_core(krate) {
+            None
+        } else if std_inject::no_std(krate) {
+            Some("core")
+        } else {
+            Some("std")
+        },
+        id_assigner: id_assigner,
+        parent_def: None,
+        resolver: resolver,
+    }.lower_crate(krate)
+}
 
+impl<'a> LoweringContext<'a> {
+    pub fn testing_context(id_assigner: &'a NodeIdAssigner, resolver: &'a mut Resolver) -> Self {
         LoweringContext {
-            crate_root: crate_root,
+            crate_root: None,
             id_assigner: id_assigner,
             parent_def: None,
             resolver: resolver,
         }
     }
 
-    pub fn lower_crate(&mut self, c: &Crate) -> hir::Crate {
+    fn lower_crate(&mut self, c: &Crate) -> hir::Crate {
         struct ItemLowerer<'lcx, 'interner: 'lcx> {
             items: BTreeMap<NodeId, hir::Item>,
             lctx: &'lcx mut LoweringContext<'interner>,

src/librustc_driver/driver.rs

@@ -37,7 +37,7 @@ use rustc_typeck as typeck;
 use rustc_privacy;
 use rustc_plugin::registry::Registry;
 use rustc_plugin as plugin;
-use rustc::hir::lowering::LoweringContext;
+use rustc::hir::lowering::lower_crate;
 use rustc_passes::{no_asm, loops, consts, rvalues, static_recursion};
 use rustc_const_eval::check_match;
 use super::Compilation;
@@ -787,8 +787,7 @@ pub fn lower_and_resolve<'a>(sess: &Session,
 
         // Lower ast -> hir.
         let hir_forest = time(sess.time_passes(), "lowering ast -> hir", || {
-            let krate = LoweringContext::new(sess, Some(krate), &mut resolver).lower_crate(krate);
-            hir_map::Forest::new(krate, dep_graph)
+            hir_map::Forest::new(lower_crate(krate, sess, &mut resolver), dep_graph)
         });
 
         (ty::CrateAnalysis {

src/librustc_metadata/astencode.rs

@@ -1329,7 +1329,7 @@ fn mk_ctxt() -> parse::ParseSess {
 fn with_testing_context<T, F: FnOnce(&mut LoweringContext) -> T>(f: F) -> T {
     let assigner = FakeNodeIdAssigner;
     let mut resolver = DummyResolver;
-    let mut lcx = LoweringContext::new(&assigner, None, &mut resolver);
+    let mut lcx = LoweringContext::testing_context(&assigner, &mut resolver);
     f(&mut lcx)
 }
 

src/librustdoc/test.rs

@@ -28,7 +28,7 @@ use rustc::hir::map as hir_map;
 use rustc::session::{self, config};
 use rustc::session::config::{get_unstable_features_setting, OutputType};
 use rustc::session::search_paths::{SearchPaths, PathKind};
-use rustc::hir::lowering::{LoweringContext, DummyResolver};
+use rustc::hir::lowering::{lower_crate, DummyResolver};
 use rustc_back::dynamic_lib::DynamicLibrary;
 use rustc_back::tempdir::TempDir;
 use rustc_driver::{driver, Compilation};
@@ -98,7 +98,7 @@ pub fn run(input: &str,
     let defs = &RefCell::new(hir_map::collect_definitions(&krate));
 
     let mut dummy_resolver = DummyResolver;
-    let krate = LoweringContext::new(&sess, Some(&krate), &mut dummy_resolver).lower_crate(&krate);
+    let krate = lower_crate(&krate, &sess, &mut dummy_resolver);
 
     let opts = scrape_test_config(&krate);