Auto merge of #48917 - petrochenkov:import, r=oli-obk

syntax: Make imports in AST closer to the source and cleanup their parsing

This is a continuation of #45846 in some sense.

src/librustc/hir/intravisit.rs

@@ -444,10 +444,10 @@ pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item) {
     visitor.visit_vis(&item.vis);
     visitor.visit_name(item.span, item.name);
     match item.node {
-        ItemExternCrate(opt_name) => {
+        ItemExternCrate(orig_name) => {
             visitor.visit_id(item.id);
-            if let Some(name) = opt_name {
-                visitor.visit_name(item.span, name);
+            if let Some(orig_name) = orig_name {
+                visitor.visit_name(item.span, orig_name);
             }
         }
         ItemUse(ref path, _) => {

src/librustc/hir/lowering.rs

@@ -879,7 +879,7 @@ impl<'a> LoweringContext<'a> {
             TyKind::Slice(ref ty) => hir::TySlice(self.lower_ty(ty, itctx)),
             TyKind::Ptr(ref mt) => hir::TyPtr(self.lower_mt(mt, itctx)),
             TyKind::Rptr(ref region, ref mt) => {
-                let span = t.span.with_hi(t.span.lo());
+                let span = t.span.shrink_to_lo();
                 let lifetime = match *region {
                     Some(ref lt) => self.lower_lifetime(lt),
                     None => self.elided_lifetime(span)
@@ -1355,17 +1355,11 @@ impl<'a> LoweringContext<'a> {
                         id: NodeId,
                         p: &Path,
                         name: Option<Name>,
-                        param_mode: ParamMode,
-                        defaults_to_global: bool)
+                        param_mode: ParamMode)
                         -> hir::Path {
-        let mut segments = p.segments.iter();
-        if defaults_to_global && p.is_global() {
-            segments.next();
-        }
-
         hir::Path {
             def: self.expect_full_def(id),
-            segments: segments.map(|segment| {
+            segments: p.segments.iter().map(|segment| {
                 self.lower_path_segment(p.span, segment, param_mode, 0,
                                         ParenthesizedGenericArgs::Err,
                                         ImplTraitContext::Disallowed)
@@ -1378,10 +1372,9 @@ impl<'a> LoweringContext<'a> {
     fn lower_path(&mut self,
                   id: NodeId,
                   p: &Path,
-                  param_mode: ParamMode,
-                  defaults_to_global: bool)
+                  param_mode: ParamMode)
                   -> hir::Path {
-        self.lower_path_extra(id, p, None, param_mode, defaults_to_global)
+        self.lower_path_extra(id, p, None, param_mode)
     }
 
     fn lower_path_segment(&mut self,
@@ -1904,7 +1897,7 @@ impl<'a> LoweringContext<'a> {
                        i: &ItemKind)
                        -> hir::Item_ {
         match *i {
-            ItemKind::ExternCrate(string) => hir::ItemExternCrate(string),
+            ItemKind::ExternCrate(orig_name) => hir::ItemExternCrate(orig_name),
             ItemKind::Use(ref use_tree) => {
                 // Start with an empty prefix
                 let prefix = Path {
@@ -2047,8 +2040,8 @@ impl<'a> LoweringContext<'a> {
         let path = &tree.prefix;
 
         match tree.kind {
-            UseTreeKind::Simple(ident) => {
-                *name = ident.name;
+            UseTreeKind::Simple(rename) => {
+                *name = tree.ident().name;
 
                 // First apply the prefix to the path
                 let mut path = Path {
@@ -2064,12 +2057,12 @@ impl<'a> LoweringContext<'a> {
                 if path.segments.len() > 1 &&
                    path.segments.last().unwrap().identifier.name == keywords::SelfValue.name() {
                     let _ = path.segments.pop();
-                    if ident.name == keywords::SelfValue.name() {
+                    if rename.is_none() {
                         *name = path.segments.last().unwrap().identifier.name;
                     }
                 }
 
-                let path = P(self.lower_path(id, &path, ParamMode::Explicit, true));
+                let path = P(self.lower_path(id, &path, ParamMode::Explicit));
                 hir::ItemUse(path, hir::UseKind::Single)
             }
             UseTreeKind::Glob => {
@@ -2080,7 +2073,7 @@ impl<'a> LoweringContext<'a> {
                         .cloned()
                         .collect(),
                     span: path.span,
-                }, ParamMode::Explicit, true));
+                }, ParamMode::Explicit));
                 hir::ItemUse(path, hir::UseKind::Glob)
             }
             UseTreeKind::Nested(ref trees) => {
@@ -2136,7 +2129,7 @@ impl<'a> LoweringContext<'a> {
                 // Privatize the degenerate import base, used only to check
                 // the stability of `use a::{};`, to avoid it showing up as
                 // a re-export by accident when `pub`, e.g. in documentation.
-                let path = P(self.lower_path(id, &prefix, ParamMode::Explicit, true));
+                let path = P(self.lower_path(id, &prefix, ParamMode::Explicit));
                 *vis = hir::Inherited;
                 hir::ItemUse(path, hir::UseKind::ListStem)
             }
@@ -3379,7 +3372,7 @@ impl<'a> LoweringContext<'a> {
             VisibilityKind::Crate(..) => hir::Visibility::Crate,
             VisibilityKind::Restricted { ref path, id, .. } => {
                 hir::Visibility::Restricted {
-                    path: P(self.lower_path(id, path, ParamMode::Explicit, true)),
+                    path: P(self.lower_path(id, path, ParamMode::Explicit)),
                     id: if let Some(owner) = explicit_owner {
                         self.lower_node_id_with_owner(id, owner).node_id
                     } else {

src/librustc/hir/mod.rs

@@ -2011,9 +2011,9 @@ pub struct Item {
 
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub enum Item_ {
-    /// An `extern crate` item, with optional original crate name,
+    /// An `extern crate` item, with optional *original* crate name if the crate was renamed.
     ///
-    /// e.g. `extern crate foo` or `extern crate foo_bar as foo`
+    /// E.g. `extern crate foo` or `extern crate foo_bar as foo`
     ItemExternCrate(Option<Name>),
 
     /// `use foo::bar::*;` or `use foo::bar::baz as quux;`

src/librustc/hir/print.rs

@@ -524,15 +524,10 @@ impl<'a> State<'a> {
         self.print_outer_attributes(&item.attrs)?;
         self.ann.pre(self, NodeItem(item))?;
         match item.node {
-            hir::ItemExternCrate(ref optional_path) => {
+            hir::ItemExternCrate(orig_name) => {
                 self.head(&visibility_qualified(&item.vis, "extern crate"))?;
-                if let Some(p) = *optional_path {
-                    let val = p.as_str();
-                    if val.contains("-") {
-                        self.print_string(&val, ast::StrStyle::Cooked)?;
-                    } else {
-                        self.print_name(p)?;
-                    }
+                if let Some(orig_name) = orig_name {
+                    self.print_name(orig_name)?;
                     self.s.space()?;
                     self.s.word("as")?;
                     self.s.space()?;

src/librustc/ich/impls_hir.rs

@@ -851,7 +851,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for hir::Item {
 }
 
 impl_stable_hash_for!(enum hir::Item_ {
-    ItemExternCrate(name),
+    ItemExternCrate(orig_name),
     ItemUse(path, use_kind),
     ItemStatic(ty, mutability, body_id),
     ItemConst(ty, body_id),

src/librustc/session/config.rs

@@ -385,7 +385,7 @@ top_level_options!(
         externs: Externs [UNTRACKED],
         crate_name: Option<String> [TRACKED],
         // An optional name to use as the crate for std during std injection,
-        // written `extern crate std = "name"`. Default to "std". Used by
+        // written `extern crate name as std`. Defaults to `std`. Used by
         // out-of-tree drivers.
         alt_std_name: Option<String> [TRACKED],
         // Indicates how the compiler should treat unstable features

src/librustc_allocator/expand.rs

@@ -99,7 +99,7 @@ impl<'a> Folder for ExpandAllocatorDirectives<'a> {
             f.cx.item_extern_crate(f.span, f.alloc),
             f.cx.item_use_simple(
                 f.span,
-                respan(f.span.empty(), VisibilityKind::Inherited),
+                respan(f.span.shrink_to_lo(), VisibilityKind::Inherited),
                 super_path,
             ),
         ];

src/librustc_driver/driver.rs

@@ -683,7 +683,7 @@ pub fn phase_2_configure_and_expand_inner<'a, F>(sess: &'a Session,
     });
 
     krate = time(sess, "crate injection", || {
-        let alt_std_name = sess.opts.alt_std_name.clone();
+        let alt_std_name = sess.opts.alt_std_name.as_ref().map(|s| &**s);
         syntax::std_inject::maybe_inject_crates_ref(krate, alt_std_name)
     });
 

src/librustc_lint/builtin.rs

@@ -1082,7 +1082,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
                     if !cx.access_levels.is_reachable(it.id) {
                         let msg = "function is marked #[no_mangle], but not exported";
                         let mut err = cx.struct_span_lint(PRIVATE_NO_MANGLE_FNS, it.span, msg);
-                        let insertion_span = it.span.with_hi(it.span.lo());
+                        let insertion_span = it.span.shrink_to_lo();
                         if it.vis == hir::Visibility::Inherited {
                             err.span_suggestion(insertion_span,
                                                 "try making it public",
@@ -1107,7 +1107,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidNoMangleItems {
                    !cx.access_levels.is_reachable(it.id) {
                        let msg = "static is marked #[no_mangle], but not exported";
                        let mut err = cx.struct_span_lint(PRIVATE_NO_MANGLE_STATICS, it.span, msg);
-                       let insertion_span = it.span.with_hi(it.span.lo());
+                       let insertion_span = it.span.shrink_to_lo();
                        if it.vis == hir::Visibility::Inherited {
                            err.span_suggestion(insertion_span,
                                                "try making it public",

src/librustc_lint/unused.rs

@@ -377,11 +377,12 @@ impl UnusedImportBraces {
             // Trigger the lint if the nested item is a non-self single item
             let node_ident;
             match items[0].0.kind {
-                ast::UseTreeKind::Simple(ident) => {
-                    if ident.name == keywords::SelfValue.name() {
+                ast::UseTreeKind::Simple(rename) => {
+                    let orig_ident = items[0].0.prefix.segments.last().unwrap().identifier;
+                    if orig_ident.name == keywords::SelfValue.name() {
                         return;
                     } else {
-                        node_ident = ident;
+                        node_ident = rename.unwrap_or(orig_ident);
                     }
                 }
                 ast::UseTreeKind::Glob => {

src/librustc_metadata/creader.rs

@@ -1055,12 +1055,14 @@ impl<'a> middle::cstore::CrateLoader for CrateLoader<'a> {
 
     fn process_item(&mut self, item: &ast::Item, definitions: &Definitions) {
         match item.node {
-            ast::ItemKind::ExternCrate(rename) => {
-                debug!("resolving extern crate stmt. ident: {} rename: {:?}", item.ident, rename);
-                let rename = match rename {
-                    Some(rename) => {
-                        validate_crate_name(Some(self.sess), &rename.as_str(), Some(item.span));
-                        rename
+            ast::ItemKind::ExternCrate(orig_name) => {
+                debug!("resolving extern crate stmt. ident: {} orig_name: {:?}",
+                       item.ident, orig_name);
+                let orig_name = match orig_name {
+                    Some(orig_name) => {
+                        validate_crate_name(Some(self.sess), &orig_name.as_str(),
+                                            Some(item.span));
+                        orig_name
                     }
                     None => item.ident.name,
                 };
@@ -1071,7 +1073,7 @@ impl<'a> middle::cstore::CrateLoader for CrateLoader<'a> {
                 };
 
                 let (cnum, ..) = self.resolve_crate(
-                    &None, item.ident.name, rename, None, item.span, PathKind::Crate, dep_kind,
+                    &None, item.ident.name, orig_name, None, item.span, PathKind::Crate, dep_kind,
                 );
 
                 let def_id = definitions.opt_local_def_id(item.id).unwrap();

src/librustc_metadata/cstore_impl.rs

@@ -533,7 +533,7 @@ impl CrateStore for cstore::CStore {
                 tokens: body.into(),
                 legacy: def.legacy,
             }),
-            vis: codemap::respan(local_span.empty(), ast::VisibilityKind::Inherited),
+            vis: codemap::respan(local_span.shrink_to_lo(), ast::VisibilityKind::Inherited),
             tokens: None,
         })
     }

src/librustc_mir/build/mod.rs

@@ -422,7 +422,7 @@ fn construct_fn<'a, 'gcx, 'tcx, A>(hir: Cx<'a, 'gcx, 'tcx>,
             builder.args_and_body(block, &arguments, arg_scope, &body.value)
         }));
         // Attribute epilogue to function's closing brace
-        let fn_end = span.with_lo(span.hi());
+        let fn_end = span.shrink_to_hi();
         let source_info = builder.source_info(fn_end);
         let return_block = builder.return_block();
         builder.cfg.terminate(block, source_info,

src/librustc_resolve/build_reduced_graph.rs

@@ -119,7 +119,8 @@ impl<'a> Resolver<'a> {
             .collect();
 
         match use_tree.kind {
-            ast::UseTreeKind::Simple(mut ident) => {
+            ast::UseTreeKind::Simple(rename) => {
+                let mut ident = use_tree.ident();
                 let mut source = module_path.pop().unwrap().node;
                 let mut type_ns_only = false;
 
@@ -142,7 +143,7 @@ impl<'a> Resolver<'a> {
                         // Replace `use foo::self;` with `use foo;`
                         let _ = module_path.pop();
                         source = last_segment.node;
-                        if ident.name == keywords::SelfValue.name() {
+                        if rename.is_none() {
                             ident = last_segment.node;
                         }
                     }
@@ -162,7 +163,7 @@ impl<'a> Resolver<'a> {
                             ModuleKind::Block(..) => unreachable!(),
                         };
                         source.name = crate_name;
-                        if ident.name == keywords::DollarCrate.name() {
+                        if rename.is_none() {
                             ident.name = crate_name;
                         }
 
@@ -206,8 +207,8 @@ impl<'a> Resolver<'a> {
 
                 // Ensure there is at most one `self` in the list
                 let self_spans = items.iter().filter_map(|&(ref use_tree, _)| {
-                    if let ast::UseTreeKind::Simple(ident) = use_tree.kind {
-                        if ident.name == keywords::SelfValue.name() {
+                    if let ast::UseTreeKind::Simple(..) = use_tree.kind {
+                        if use_tree.ident().name == keywords::SelfValue.name() {
                             return Some(use_tree.span);
                         }
                     }
@@ -244,9 +245,9 @@ impl<'a> Resolver<'a> {
 
         match item.node {
             ItemKind::Use(ref use_tree) => {
-                // Just an empty prefix to start out
+                // Imports are resolved as global by default, add starting root segment.
                 let prefix = ast::Path {
-                    segments: vec![],
+                    segments: use_tree.prefix.make_root().into_iter().collect(),
                     span: use_tree.span,
                 };
 
@@ -255,7 +256,7 @@ impl<'a> Resolver<'a> {
                 );
             }
 
-            ItemKind::ExternCrate(as_name) => {
+            ItemKind::ExternCrate(orig_name) => {
                 self.crate_loader.process_item(item, &self.definitions);
 
                 // n.b. we don't need to look at the path option here, because cstore already did
@@ -274,7 +275,7 @@ impl<'a> Resolver<'a> {
                     id: item.id,
                     parent,
                     imported_module: Cell::new(Some(module)),
-                    subclass: ImportDirectiveSubclass::ExternCrate(as_name),
+                    subclass: ImportDirectiveSubclass::ExternCrate(orig_name),
                     span: item.span,
                     module_path: Vec::new(),
                     vis: Cell::new(vis),