rustc_resolve: don't allow ::crate_name to bypass extern_prelude.

src/librustc_resolve/resolve_imports.rs

@@ -196,7 +196,11 @@ impl<'a, 'crateloader> Resolver<'a, 'crateloader> {
                     }
 
                     // Fall back to resolving to an external crate.
-                    if !(ns == TypeNS && self.extern_prelude.contains(&ident.name)) {
+                    if !(
+                        ns == TypeNS &&
+                        !ident.is_path_segment_keyword() &&
+                        self.extern_prelude.contains(&ident.name)
+                    ) {
                         // ... unless the crate name is not in the `extern_prelude`.
                         return binding;
                     }
@@ -211,7 +215,11 @@ impl<'a, 'crateloader> Resolver<'a, 'crateloader> {
                     )
                 {
                     self.resolve_crate_root(ident)
-                } else if ns == TypeNS && !ident.is_path_segment_keyword() {
+                } else if
+                    ns == TypeNS &&
+                    !ident.is_path_segment_keyword() &&
+                    self.extern_prelude.contains(&ident.name)
+                {
                     let crate_id =
                         self.crate_loader.process_path_extern(ident.name, ident.span);
                     self.get_module(DefId { krate: crate_id, index: CRATE_DEF_INDEX })

src/test/run-make-fulldeps/save-analysis-rfc2126/Makefile

@@ -1,9 +1,11 @@
 -include ../tools.mk
 
 all: extern_absolute_paths.rs extern_in_paths.rs krate2
-	$(RUSTC) extern_absolute_paths.rs -Zsave-analysis --edition=2018
+	$(RUSTC) extern_absolute_paths.rs -Zsave-analysis --edition=2018 \
+		-Z unstable-options --extern krate2
 	cat $(TMPDIR)/save-analysis/extern_absolute_paths.json | "$(PYTHON)" validate_json.py
-	$(RUSTC) extern_in_paths.rs -Zsave-analysis --edition=2018
+	$(RUSTC) extern_in_paths.rs -Zsave-analysis --edition=2018 \
+		-Z unstable-options --extern krate2
 	cat $(TMPDIR)/save-analysis/extern_in_paths.json | "$(PYTHON)" validate_json.py
 
 krate2: krate2.rs

src/test/ui/issues/issue-52489.rs

@@ -10,6 +10,7 @@
 
 // edition:2018
 // aux-build:issue-52489.rs
+// compile-flags:--extern issue_52489
 
 use issue_52489;
 //~^ ERROR use of unstable library feature 'issue_52489_unstable'

src/test/ui/issues/issue-52489.stderr

@@ -1,5 +1,5 @@
 error[E0658]: use of unstable library feature 'issue_52489_unstable'
-  --> $DIR/issue-52489.rs:14:5
+  --> $DIR/issue-52489.rs:15:5
    |
 LL | use issue_52489;
    |     ^^^^^^^^^^^

src/test/ui/rfc-2126-extern-absolute-paths/non-existent-1.rs

@@ -10,6 +10,6 @@
 
 // edition:2018
 
-use xcrate::S; //~ ERROR can't find crate for `xcrate`
+use xcrate::S; //~ ERROR unresolved import `xcrate`
 
 fn main() {}

src/test/ui/rfc-2126-extern-absolute-paths/non-existent-1.stderr

@@ -1,9 +1,9 @@
-error[E0463]: can't find crate for `xcrate`
+error[E0432]: unresolved import `xcrate`
   --> $DIR/non-existent-1.rs:13:5
    |
-LL | use xcrate::S; //~ ERROR can't find crate for `xcrate`
-   |     ^^^^^^ can't find crate
+LL | use xcrate::S; //~ ERROR unresolved import `xcrate`
+   |     ^^^^^^ Could not find `xcrate` in `{{root}}`
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0463`.
+For more information about this error, try `rustc --explain E0432`.

src/test/ui/rfc-2126-extern-absolute-paths/non-existent-2.rs

@@ -11,5 +11,6 @@
 // edition:2018
 
 fn main() {
-    let s = ::xcrate::S; //~ ERROR can't find crate for `xcrate`
+    let s = ::xcrate::S;
+    //~^ ERROR failed to resolve. Could not find `xcrate` in `{{root}}`
 }

src/test/ui/rfc-2126-extern-absolute-paths/non-existent-2.stderr

@@ -1,9 +1,9 @@
-error[E0463]: can't find crate for `xcrate`
+error[E0433]: failed to resolve. Could not find `xcrate` in `{{root}}`
   --> $DIR/non-existent-2.rs:14:15
    |
-LL |     let s = ::xcrate::S; //~ ERROR can't find crate for `xcrate`
-   |               ^^^^^^ can't find crate
+LL |     let s = ::xcrate::S;
+   |               ^^^^^^ Could not find `xcrate` in `{{root}}`
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0463`.
+For more information about this error, try `rustc --explain E0433`.

src/test/ui/rfc-2126-extern-absolute-paths/non-existent-3.rs

@@ -10,6 +10,6 @@
 
 // edition:2018
 
-use ycrate; //~ ERROR can't find crate for `ycrate`
+use ycrate; //~ ERROR unresolved import `ycrate`
 
 fn main() {}

src/test/ui/rfc-2126-extern-absolute-paths/non-existent-3.stderr

@@ -1,9 +1,9 @@
-error[E0463]: can't find crate for `ycrate`
+error[E0432]: unresolved import `ycrate`
   --> $DIR/non-existent-3.rs:13:5
    |
-LL | use ycrate; //~ ERROR can't find crate for `ycrate`
-   |     ^^^^^^ can't find crate
+LL | use ycrate; //~ ERROR unresolved import `ycrate`
+   |     ^^^^^^ no `ycrate` external crate
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0463`.
+For more information about this error, try `rustc --explain E0432`.

src/test/ui/rfc-2126-extern-absolute-paths/single-segment.rs

@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // aux-build:xcrate.rs
+// compile-flags:--extern xcrate
 // edition:2018
 
 use crate; //~ ERROR crate root imports need to be explicitly named: `use crate as name;`

src/test/ui/rfc-2126-extern-absolute-paths/single-segment.stderr

@@ -1,17 +1,17 @@
 error: crate root imports need to be explicitly named: `use crate as name;`
-  --> $DIR/single-segment.rs:14:5
+  --> $DIR/single-segment.rs:15:5
    |
 LL | use crate; //~ ERROR crate root imports need to be explicitly named: `use crate as name;`
    |     ^^^^^
 
 error: cannot glob-import all possible crates
-  --> $DIR/single-segment.rs:15:5
+  --> $DIR/single-segment.rs:16:5
    |
 LL | use *; //~ ERROR cannot glob-import all possible crates
    |     ^
 
 error[E0423]: expected value, found module `xcrate`
-  --> $DIR/single-segment.rs:18:13
+  --> $DIR/single-segment.rs:19:13
    |
 LL |     let s = ::xcrate; //~ ERROR expected value, found module `xcrate`
    |             ^^^^^^^^ not a value

src/test/ui/rfc-2126-extern-in-paths/non-existent-1.rs

@@ -10,6 +10,6 @@
 
 #![feature(extern_in_paths)]
 
-use extern::xcrate::S; //~ ERROR can't find crate for `xcrate`
+use extern::xcrate::S; //~ ERROR unresolved import `extern::xcrate`
 
 fn main() {}

src/test/ui/rfc-2126-extern-in-paths/non-existent-1.stderr

@@ -1,9 +1,9 @@
-error[E0463]: can't find crate for `xcrate`
+error[E0432]: unresolved import `extern::xcrate`
   --> $DIR/non-existent-1.rs:13:13
    |
-LL | use extern::xcrate::S; //~ ERROR can't find crate for `xcrate`
-   |             ^^^^^^ can't find crate
+LL | use extern::xcrate::S; //~ ERROR unresolved import `extern::xcrate`
+   |             ^^^^^^ Could not find `xcrate` in `extern`
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0463`.
+For more information about this error, try `rustc --explain E0432`.

src/test/ui/rfc-2126-extern-in-paths/non-existent-2.rs

@@ -11,5 +11,6 @@
 #![feature(extern_in_paths)]
 
 fn main() {
-    let s = extern::xcrate::S; //~ ERROR can't find crate for `xcrate`
+    let s = extern::xcrate::S;
+    //~^ ERROR failed to resolve. Could not find `xcrate` in `extern`
 }

src/test/ui/rfc-2126-extern-in-paths/non-existent-2.stderr

@@ -1,9 +1,9 @@
-error[E0463]: can't find crate for `xcrate`
+error[E0433]: failed to resolve. Could not find `xcrate` in `extern`
   --> $DIR/non-existent-2.rs:14:21
    |
-LL |     let s = extern::xcrate::S; //~ ERROR can't find crate for `xcrate`
-   |                     ^^^^^^ can't find crate
+LL |     let s = extern::xcrate::S;
+   |                     ^^^^^^ Could not find `xcrate` in `extern`
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0463`.
+For more information about this error, try `rustc --explain E0433`.

src/test/ui/rfc-2126-extern-in-paths/non-existent-3.rs

@@ -10,6 +10,6 @@
 
 #![feature(extern_in_paths)]
 
-use extern::ycrate; //~ ERROR can't find crate for `ycrate`
+use extern::ycrate; //~ ERROR unresolved import `extern::ycrate`
 
 fn main() {}

src/test/ui/rfc-2126-extern-in-paths/non-existent-3.stderr

@@ -1,9 +1,9 @@
-error[E0463]: can't find crate for `ycrate`
-  --> $DIR/non-existent-3.rs:13:13
+error[E0432]: unresolved import `extern::ycrate`
+  --> $DIR/non-existent-3.rs:13:5
    |
-LL | use extern::ycrate; //~ ERROR can't find crate for `ycrate`
-   |             ^^^^^^ can't find crate
+LL | use extern::ycrate; //~ ERROR unresolved import `extern::ycrate`
+   |     ^^^^^^^^^^^^^^ no `ycrate` external crate
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0463`.
+For more information about this error, try `rustc --explain E0432`.

src/test/ui/rfc-2126-extern-in-paths/single-segment.rs

@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // aux-build:xcrate.rs
+// compile-flags:--extern xcrate
 
 #![feature(extern_in_paths)]
 

src/test/ui/rfc-2126-extern-in-paths/single-segment.stderr

@@ -1,17 +1,17 @@
 error: cannot glob-import all possible crates
-  --> $DIR/single-segment.rs:17:5
+  --> $DIR/single-segment.rs:18:5
    |
 LL | use extern::*; //~ ERROR cannot glob-import all possible crates
    |     ^^^^^^^^^
 
 error[E0432]: unresolved import `extern`
-  --> $DIR/single-segment.rs:15:5
+  --> $DIR/single-segment.rs:16:5
    |
 LL | use extern; //~ ERROR unresolved import `extern`
    |     ^^^^^^ no `extern` in the root
 
 error[E0423]: expected value, found module `extern::xcrate`
-  --> $DIR/single-segment.rs:20:13
+  --> $DIR/single-segment.rs:21:13
    |
 LL |     let s = extern::xcrate; //~ ERROR expected value, found module `extern::xcrate`
    |             ^^^^^^^^^^^^^^ not a value

src/test/ui/run-pass/issues/issue-52140/main.rs

@@ -10,6 +10,7 @@
 
 // run-pass
 // aux-build:some_crate.rs
+// compile-flags:--extern some_crate
 // edition:2018
 
 mod foo {

src/test/ui/run-pass/issues/issue-52141/main.rs

@@ -10,6 +10,7 @@
 
 // run-pass
 // aux-build:some_crate.rs
+// compile-flags:--extern some_crate
 // edition:2018
 
 use some_crate as some_name;

src/test/ui/run-pass/issues/issue-52705/main.rs

@@ -10,6 +10,7 @@
 
 // run-pass
 // aux-build:png2.rs
+// compile-flags:--extern png2
 // edition:2018
 
 mod png {

src/test/ui/run-pass/rfcs/rfc-2126-extern-absolute-paths/basic.rs

@@ -10,6 +10,7 @@
 
 // run-pass
 // aux-build:xcrate.rs
+// compile-flags:--extern xcrate
 // edition:2018
 
 use xcrate::Z;

src/test/ui/run-pass/rfcs/rfc-2126-extern-absolute-paths/extern.rs

@@ -10,6 +10,7 @@
 
 // run-pass
 // aux-build:xcrate.rs
+// compile-flags:--extern xcrate
 
 #![feature(extern_in_paths)]
 

src/test/ui/rust-2018/extern-crate-idiomatic-in-2018.fixed

@@ -10,6 +10,7 @@
 
 // aux-build:edition-lint-paths.rs
 // run-rustfix
+// compile-flags:--extern edition_lint_paths
 // edition:2018
 
 // The "normal case". Ideally we would remove the `extern crate` here,

src/test/ui/rust-2018/extern-crate-idiomatic-in-2018.rs

@@ -10,6 +10,7 @@
 
 // aux-build:edition-lint-paths.rs
 // run-rustfix
+// compile-flags:--extern edition_lint_paths
 // edition:2018
 
 // The "normal case". Ideally we would remove the `extern crate` here,

src/test/ui/rust-2018/extern-crate-idiomatic-in-2018.stderr

@@ -1,18 +1,18 @@
 error: unused extern crate
-  --> $DIR/extern-crate-idiomatic-in-2018.rs:21:1
+  --> $DIR/extern-crate-idiomatic-in-2018.rs:22:1
    |
 LL | extern crate edition_lint_paths;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove it
    |
 note: lint level defined here
-  --> $DIR/extern-crate-idiomatic-in-2018.rs:18:9
+  --> $DIR/extern-crate-idiomatic-in-2018.rs:19:9
    |
 LL | #![deny(rust_2018_idioms)]
    |         ^^^^^^^^^^^^^^^^
    = note: #[deny(unused_extern_crates)] implied by #[deny(rust_2018_idioms)]
 
 error: `extern crate` is not idiomatic in the new edition
-  --> $DIR/extern-crate-idiomatic-in-2018.rs:24:1
+  --> $DIR/extern-crate-idiomatic-in-2018.rs:25:1
    |
 LL | extern crate edition_lint_paths as bar;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: convert it to a `use`

src/test/ui/rust-2018/extern-crate-idiomatic.fixed

@@ -10,6 +10,7 @@
 
 // run-pass
 // aux-build:edition-lint-paths.rs
+// compile-flags:--extern edition_lint_paths
 // run-rustfix
 
 // The "normal case". Ideally we would remove the `extern crate` here,

src/test/ui/rust-2018/extern-crate-idiomatic.rs

@@ -10,6 +10,7 @@
 
 // run-pass
 // aux-build:edition-lint-paths.rs
+// compile-flags:--extern edition_lint_paths
 // run-rustfix
 
 // The "normal case". Ideally we would remove the `extern crate` here,

src/test/ui/rust-2018/issue-54006.rs

@@ -0,0 +1,23 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// edition:2018
+
+#![no_std]
+#![crate_type = "lib"]
+
+use alloc::vec;
+//~^ ERROR unresolved import `alloc`
+
+pub fn foo() {
+    let mut xs = vec![];
+    //~^ ERROR cannot determine resolution for the macro `vec`
+    xs.push(0);
+}

src/test/ui/rust-2018/issue-54006.stderr

@@ -0,0 +1,17 @@
+error[E0432]: unresolved import `alloc`
+  --> $DIR/issue-54006.rs:16:5
+   |
+LL | use alloc::vec;
+   |     ^^^^^ Could not find `alloc` in `{{root}}`
+
+error: cannot determine resolution for the macro `vec`
+  --> $DIR/issue-54006.rs:20:18
+   |
+LL |     let mut xs = vec![];
+   |                  ^^^
+   |
+   = note: import resolution is stuck, try simplifying macro imports
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0432`.

src/test/ui/rust-2018/remove-extern-crate.fixed

@@ -12,6 +12,7 @@
 // edition:2018
 // compile-pass
 // aux-build:remove-extern-crate.rs
+// compile-flags:--extern remove_extern_crate --extern core
 
 #![warn(rust_2018_idioms)]
 

src/test/ui/rust-2018/remove-extern-crate.rs

@@ -12,6 +12,7 @@
 // edition:2018
 // compile-pass
 // aux-build:remove-extern-crate.rs
+// compile-flags:--extern remove_extern_crate --extern core
 
 #![warn(rust_2018_idioms)]