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 https://github.com/rust-lang/rust/pull/45846 in some sense.

6 files changed, 23 insertions, 35 deletions

diff --git a/src/librustc/hir/intravisit.rs b/src/librustc/hir/intravisit.rs
index b804cf7bf5a..972278bdf86 100644
--- a/src/librustc/hir/intravisit.rs
+++ b/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, _) => {
diff --git a/src/librustc/hir/lowering.rs b/src/librustc/hir/lowering.rs
index 49611689fc4..1439410f7e9 100644
--- a/src/librustc/hir/lowering.rs
+++ b/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 {
diff --git a/src/librustc/hir/mod.rs b/src/librustc/hir/mod.rs
index 83e855178db..5ae84f5685e 100644
--- a/src/librustc/hir/mod.rs
+++ b/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;`
diff --git a/src/librustc/hir/print.rs b/src/librustc/hir/print.rs
index 9e755f366a7..3d38c0c8ed9 100644
--- a/src/librustc/hir/print.rs
+++ b/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()?;
diff --git a/src/librustc/ich/impls_hir.rs b/src/librustc/ich/impls_hir.rs
index c085b803085..e764cedd658 100644
--- a/src/librustc/ich/impls_hir.rs
+++ b/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),
diff --git a/src/librustc/session/config.rs b/src/librustc/session/config.rs
index 2cf09a002c9..0d91074e946 100644
--- a/src/librustc/session/config.rs
+++ b/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