Avoid recording unnameable extern crate aliases in diagnostic metadata

compiler/rustc_metadata/src/creader.rs

@@ -15,7 +15,7 @@ use rustc_data_structures::sync::{self, FreezeReadGuard, FreezeWriteGuard};
 use rustc_data_structures::unord::UnordMap;
 use rustc_expand::base::SyntaxExtension;
 use rustc_hir::def_id::{CrateNum, LOCAL_CRATE, LocalDefId, StableCrateId};
-use rustc_hir::definitions::Definitions;
+use rustc_hir::definitions::{DefPathData, Definitions};
 use rustc_index::IndexVec;
 use rustc_lint_defs as lint;
 use rustc_lint_defs::builtin::UNUSED_CRATE_DEPENDENCIES;
@@ -1358,14 +1358,24 @@ impl CStore {
                 let cnum =
                     self.resolve_crate(tcx, name, item.span, dep_kind, CrateOrigin::Extern)?;
 
-                let path_len = definitions.def_path(def_id).data.len();
+                let def_path = definitions.def_path(def_id);
+                // An extern crate is only globally nameable if every segment in its path
+                // is in the type namespace (i.e., it is purely nested inside modules).
+                // If any segment is in the value namespace (e.g. inside a fn or const),
+                // it is unnameable from outside that block.
+                let is_unnameable =
+                    def_path.data.iter().any(|d| !matches!(d.data, DefPathData::TypeNs(_)));
                 self.update_extern_crate(
                     cnum,
                     name,
                     ExternCrate {
-                        src: ExternCrateSource::Extern(def_id.to_def_id()),
+                        src: if is_unnameable {
+                            ExternCrateSource::Path
+                        } else {
+                            ExternCrateSource::Extern(def_id.to_def_id())
+                        },
                         span: item.span,
-                        path_len,
+                        path_len: if is_unnameable { usize::MAX } else { def_path.data.len() },
                         dependency_of: LOCAL_CRATE,
                     },
                 );

tests/ui/imports/auxiliary/macro-generated-extern-crate.rs

@@ -0,0 +1,3 @@
+pub trait MyTrait {
+    fn custom() {}
+}

tests/ui/imports/macro-generated-extern-crate.rs

@@ -0,0 +1,14 @@
+//@ edition: 2021
+//@ aux-build: macro-generated-extern-crate.rs
+
+const _: () = {
+    extern crate macro_generated_extern_crate as _my_crate;
+    impl _my_crate::MyTrait for Local {}
+};
+
+struct Local;
+
+fn main() {
+    Local::custom();
+    //~^ ERROR no associated function or constant named `custom` found for struct `Local`
+}

tests/ui/imports/macro-generated-extern-crate.stderr

@@ -0,0 +1,18 @@
+error[E0599]: no associated function or constant named `custom` found for struct `Local` in the current scope
+  --> $DIR/macro-generated-extern-crate.rs:12:12
+   |
+LL | struct Local;
+   | ------------ associated function or constant `custom` not found for this struct
+...
+LL |     Local::custom();
+   |            ^^^^^^ associated function or constant not found in `Local`
+   |
+   = help: items from traits can only be used if the trait is in scope
+help: trait `MyTrait` which provides `custom` is implemented but not in scope; perhaps you want to import it
+   |
+LL + use macro_generated_extern_crate::MyTrait;
+   |
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0599`.

tests/ui/rust-2018/uniform-paths/issue-87932.stderr

@@ -10,7 +10,7 @@ LL |     A::deserialize();
    = help: items from traits can only be used if the trait is in scope
 help: trait `Deserialize` which provides `deserialize` is implemented but not in scope; perhaps you want to import it
    |
-LL + use <crate::A as issue_87932_a::Deserialize>::deserialize::_a::Deserialize;
+LL + use issue_87932_a::Deserialize;
    |
 
 error: aborting due to 1 previous error

tests/ui/traits/bound/same-crate-name.rs

@@ -32,32 +32,23 @@ fn main() {
         extern crate crate_a1 as a;
         a::try_foo(foo);
         //~^ ERROR E0277
-        //~| NOTE there are multiple different versions of crate `crate_a1` in the dependency graph
-        //~| HELP you can use `cargo tree` to explore your dependency tree
 
         // We don't want to see the "version mismatch" help message here
         // because `implements_no_traits` has no impl for `Foo`
         a::try_foo(implements_no_traits);
         //~^ ERROR E0277
-        //~| NOTE there are multiple different versions of crate `crate_a1` in the dependency graph
-        //~| HELP you can use `cargo tree` to explore your dependency tree
 
         // We don't want to see the "version mismatch" help message here
         // because `other_variant_implements_mismatched_trait`
         // does not have an impl for its `<isize>` variant,
         // only for its `<usize>` variant.
         a::try_foo(other_variant_implements_mismatched_trait);
         //~^ ERROR E0277
-        //~| NOTE there are multiple different versions of crate `crate_a1` in the dependency graph
-        //~| HELP you can use `cargo tree` to explore your dependency tree
 
         // We don't want to see the "version mismatch" help message here
         // because `ImplementsTraitForUsize` only has
         // impls for the correct trait where the path is not misleading.
         a::try_foo(other_variant_implements_correct_trait);
         //~^ ERROR E0277
-        //~| HELP the trait `main::a::Bar` is implemented for `ImplementsTraitForUsize<usize>`
-        //~| NOTE there are multiple different versions of crate `crate_a1` in the dependency graph
-        //~| HELP you can use `cargo tree` to explore your dependency tree
     }
 }

tests/ui/traits/bound/same-crate-name.stderr

@@ -1,23 +1,13 @@
-error[E0277]: the trait bound `Foo: main::a::Bar` is not satisfied
+error[E0277]: the trait bound `Foo: crate_a1::Bar` is not satisfied
   --> $DIR/same-crate-name.rs:33:20
    |
 LL |         a::try_foo(foo);
-   |         ---------- ^^^ the trait `main::a::Bar` is not implemented for `Foo`
+   |         ---------- ^^^ the trait `crate_a1::Bar` is not implemented for `Foo`
    |         |
    |         required by a bound introduced by this call
    |
-note: there are multiple different versions of crate `crate_a1` in the dependency graph
-  --> $DIR/auxiliary/crate_a1.rs:1:1
-   |
-LL | pub trait Bar {}
-   | ^^^^^^^^^^^^^ this is the expected trait
-   |
-  ::: $DIR/auxiliary/crate_a2.rs:3:1
-   |
-LL | pub trait Bar {}
-   | ------------- this is the found trait
-   = help: you can use `cargo tree` to explore your dependency tree
-help: the trait `main::a::Bar` is implemented for `ImplementsTraitForUsize<usize>`
+   = note: `Foo` implements similarly named trait `crate_a2::Bar`, but not `crate_a1::Bar`
+help: the trait `crate_a1::Bar` is implemented for `ImplementsTraitForUsize<usize>`
   --> $DIR/auxiliary/crate_a1.rs:9:1
    |
 LL | impl Bar for ImplementsTraitForUsize<usize> {}
@@ -28,26 +18,15 @@ note: required by a bound in `try_foo`
 LL | pub fn try_foo(x: impl Bar) {}
    |                        ^^^ required by this bound in `try_foo`
 
-error[E0277]: the trait bound `DoesNotImplementTrait: main::a::Bar` is not satisfied
-  --> $DIR/same-crate-name.rs:40:20
+error[E0277]: the trait bound `DoesNotImplementTrait: crate_a1::Bar` is not satisfied
+  --> $DIR/same-crate-name.rs:38:20
    |
 LL |         a::try_foo(implements_no_traits);
-   |         ---------- ^^^^^^^^^^^^^^^^^^^^ the trait `main::a::Bar` is not implemented for `DoesNotImplementTrait`
+   |         ---------- ^^^^^^^^^^^^^^^^^^^^ the trait `crate_a1::Bar` is not implemented for `DoesNotImplementTrait`
    |         |
    |         required by a bound introduced by this call
    |
-note: there are multiple different versions of crate `crate_a1` in the dependency graph
-  --> $DIR/auxiliary/crate_a1.rs:1:1
-   |
-LL | pub trait Bar {}
-   | ^^^^^^^^^^^^^ this is the expected trait
-   |
-  ::: $DIR/auxiliary/crate_a2.rs:3:1
-   |
-LL | pub trait Bar {}
-   | ------------- this is the trait that was imported
-   = help: you can use `cargo tree` to explore your dependency tree
-help: the trait `main::a::Bar` is implemented for `ImplementsTraitForUsize<usize>`
+help: the trait `crate_a1::Bar` is implemented for `ImplementsTraitForUsize<usize>`
   --> $DIR/auxiliary/crate_a1.rs:9:1
    |
 LL | impl Bar for ImplementsTraitForUsize<usize> {}
@@ -58,26 +37,16 @@ note: required by a bound in `try_foo`
 LL | pub fn try_foo(x: impl Bar) {}
    |                        ^^^ required by this bound in `try_foo`
 
-error[E0277]: the trait bound `ImplementsWrongTraitConditionally<isize>: main::a::Bar` is not satisfied
-  --> $DIR/same-crate-name.rs:49:20
+error[E0277]: the trait bound `ImplementsWrongTraitConditionally<isize>: crate_a1::Bar` is not satisfied
+  --> $DIR/same-crate-name.rs:45:20
    |
 LL |         a::try_foo(other_variant_implements_mismatched_trait);
-   |         ---------- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `main::a::Bar` is not implemented for `ImplementsWrongTraitConditionally<isize>`
+   |         ---------- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `crate_a1::Bar` is not implemented for `ImplementsWrongTraitConditionally<isize>`
    |         |
    |         required by a bound introduced by this call
    |
-note: there are multiple different versions of crate `crate_a1` in the dependency graph
-  --> $DIR/auxiliary/crate_a1.rs:1:1
-   |
-LL | pub trait Bar {}
-   | ^^^^^^^^^^^^^ this is the expected trait
-   |
-  ::: $DIR/auxiliary/crate_a2.rs:3:1
-   |
-LL | pub trait Bar {}
-   | ------------- this is the found trait
-   = help: you can use `cargo tree` to explore your dependency tree
-help: the trait `main::a::Bar` is implemented for `ImplementsTraitForUsize<usize>`
+   = note: `ImplementsWrongTraitConditionally<isize>` implements similarly named trait `crate_a2::Bar`, but not `crate_a1::Bar`
+help: the trait `crate_a1::Bar` is implemented for `ImplementsTraitForUsize<usize>`
   --> $DIR/auxiliary/crate_a1.rs:9:1
    |
 LL | impl Bar for ImplementsTraitForUsize<usize> {}
@@ -88,26 +57,15 @@ note: required by a bound in `try_foo`
 LL | pub fn try_foo(x: impl Bar) {}
    |                        ^^^ required by this bound in `try_foo`
 
-error[E0277]: the trait bound `ImplementsTraitForUsize<isize>: main::a::Bar` is not satisfied
-  --> $DIR/same-crate-name.rs:57:20
+error[E0277]: the trait bound `ImplementsTraitForUsize<isize>: crate_a1::Bar` is not satisfied
+  --> $DIR/same-crate-name.rs:51:20
    |
 LL |         a::try_foo(other_variant_implements_correct_trait);
-   |         ---------- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `main::a::Bar` is not implemented for `ImplementsTraitForUsize<isize>`
+   |         ---------- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `crate_a1::Bar` is not implemented for `ImplementsTraitForUsize<isize>`
    |         |
    |         required by a bound introduced by this call
    |
-note: there are multiple different versions of crate `crate_a1` in the dependency graph
-  --> $DIR/auxiliary/crate_a1.rs:1:1
-   |
-LL | pub trait Bar {}
-   | ^^^^^^^^^^^^^ this is the expected trait
-   |
-  ::: $DIR/auxiliary/crate_a2.rs:3:1
-   |
-LL | pub trait Bar {}
-   | ------------- this is the trait that was imported
-   = help: you can use `cargo tree` to explore your dependency tree
-help: the trait `main::a::Bar` is implemented for `ImplementsTraitForUsize<usize>`
+help: the trait `crate_a1::Bar` is implemented for `ImplementsTraitForUsize<usize>`
   --> $DIR/auxiliary/crate_a1.rs:9:1
    |
 LL | impl Bar for ImplementsTraitForUsize<usize> {}

tests/ui/type/type-mismatch-same-crate-name.rs

@@ -16,17 +16,18 @@ fn main() {
         extern crate crate_a1 as a;
         a::try_foo(foo2);
         //~^ ERROR mismatched types
-        //~| NOTE expected `main::a::Foo`, found a different `main::a::Foo`
+        //~| NOTE expected `crate_a1::Foo`, found `crate_a2::Foo`
         //~| NOTE arguments to this function are incorrect
-        //~| NOTE there are multiple different versions of crate `crate_a1` in the dependency graph
+        //~| NOTE `crate_a2::Foo` and `crate_a1::Foo` have similar names, but are actually distinct types
+        //~| NOTE `crate_a2::Foo` is defined in crate `crate_a2`
+        //~| NOTE `crate_a1::Foo` is defined in crate `crate_a1`
         //~| NOTE function defined here
-        //~| HELP you can use `cargo tree` to explore your dependency tree
         a::try_bar(bar2);
         //~^ ERROR mismatched types
-        //~| NOTE expected trait `main::a::Bar`, found a different trait `main::a::Bar`
+        //~| NOTE expected trait `crate_a1::Bar`, found trait `crate_a2::Bar`
         //~| NOTE arguments to this function are incorrect
-        //~| NOTE there are multiple different versions of crate `crate_a1` in the dependency graph
+        //~| NOTE expected struct `Box<(dyn crate_a1::Bar + 'static)>`
+        //~| NOTE    found struct `Box<dyn crate_a2::Bar>`
         //~| NOTE function defined here
-        //~| HELP you can use `cargo tree` to explore your dependency tree
     }
 }

tests/ui/type/type-mismatch-same-crate-name.stderr

@@ -2,46 +2,37 @@ error[E0308]: mismatched types
   --> $DIR/type-mismatch-same-crate-name.rs:17:20
    |
 LL |         a::try_foo(foo2);
-   |         ---------- ^^^^ expected `main::a::Foo`, found a different `main::a::Foo`
+   |         ---------- ^^^^ expected `crate_a1::Foo`, found `crate_a2::Foo`
    |         |
    |         arguments to this function are incorrect
    |
-note: there are multiple different versions of crate `crate_a1` in the dependency graph
-  --> $DIR/auxiliary/crate_a1.rs:1:1
+   = note: `crate_a2::Foo` and `crate_a1::Foo` have similar names, but are actually distinct types
+note: `crate_a2::Foo` is defined in crate `crate_a2`
+  --> $DIR/auxiliary/crate_a2.rs:1:1
    |
 LL | pub struct Foo;
-   | ^^^^^^^^^^^^^^ this is the expected type
-   |
-  ::: $DIR/auxiliary/crate_a2.rs:1:1
+   | ^^^^^^^^^^^^^^
+note: `crate_a1::Foo` is defined in crate `crate_a1`
+  --> $DIR/auxiliary/crate_a1.rs:1:1
    |
 LL | pub struct Foo;
-   | -------------- this is the found type
-   = help: you can use `cargo tree` to explore your dependency tree
+   | ^^^^^^^^^^^^^^
 note: function defined here
   --> $DIR/auxiliary/crate_a1.rs:10:8
    |
 LL | pub fn try_foo(x: Foo){}
    |        ^^^^^^^
 
 error[E0308]: mismatched types
-  --> $DIR/type-mismatch-same-crate-name.rs:24:20
+  --> $DIR/type-mismatch-same-crate-name.rs:25:20
    |
 LL |         a::try_bar(bar2);
-   |         ---------- ^^^^ expected trait `main::a::Bar`, found a different trait `main::a::Bar`
+   |         ---------- ^^^^ expected trait `crate_a1::Bar`, found trait `crate_a2::Bar`
    |         |
    |         arguments to this function are incorrect
    |
-note: there are multiple different versions of crate `crate_a1` in the dependency graph
-  --> $DIR/auxiliary/crate_a1.rs:3:1
-   |
-LL | pub trait Bar {}
-   | ^^^^^^^^^^^^^ this is the expected trait
-   |
-  ::: $DIR/auxiliary/crate_a2.rs:3:1
-   |
-LL | pub trait Bar {}
-   | ------------- this is the found trait
-   = help: you can use `cargo tree` to explore your dependency tree
+   = note: expected struct `Box<(dyn crate_a1::Bar + 'static)>`
+              found struct `Box<dyn crate_a2::Bar>`
 note: function defined here
   --> $DIR/auxiliary/crate_a1.rs:11:8
    |