resolve: Improve duplicate glob detection
This fixes a bug introduced in #31726 in which we erroneously allow multiple imports of the same item under some circumstances.
More specifically, we erroneously allow a module that is in a cycle of glob re-exports to have other re-exports (besides the glob from the cycle).
For example,
```rust
pub fn f() {}
mod foo {
pub use f; // (1) This defines `foo::f`.
pub use bar::*; // (3) This also defines `foo::f`, which should be a duplicate error but is currently allowed.
}
mod bar {
pub use foo::*; // (2) This defines `bar::f`.
}
```
A module in a glob re-export cycle can still have `pub` items after this PR. For example,
```rust
mod foo {
pub fn f() {}; // (1) This defines `foo::f`.
pub use bar::*; // (3) This is not a duplicate error since items shadow glob-imported re-exports (cf #31337).
}
mod bar {
pub use foo::*; // (2) This defines `bar::f`.
}
```
r? @nikomatsakis
Disallow methods from traits that are not in scope
This PR only allows a trait method to be used if the trait is in scope (fixes#31379).
This is a [breaking-change]. For example, the following would break:
```rust
mod foo {
pub trait T { fn f(&self) {} }
impl T for () {}
}
mod bar { pub use foo::T; }
fn main() {
pub use bar::*;
struct T; // This shadows the trait `T`,
().f() // making this an error.
}
```
r? @nikomatsakis
Fix name resolution in lexical scopes
Currently, `resolve_item_in_lexical_scope` does not check the "ribs" (type parameters and local variables). This can allow items that should be shadowed by type parameters to be named.
For example,
```rust
struct T { i: i32 }
fn f<T>() {
let t = T { i: 0 }; // This use of `T` resolves to the struct, not the type parameter
}
mod Foo {
pub fn f() {}
}
fn g<Foo>() {
Foo::f(); // This use of `Foo` resolves to the module, not the type parameter
}
```
This PR changes `resolve_item_in_lexical_scope` so that it fails when the item is shadowed by a rib (fixes#32120).
This is a [breaking-change], but it looks unlikely to cause breakage in practice.
r? @nikomatsakis
Forbid glob-importing from a type alias
This PR forbids glob-importing from a type alias or trait (fixes#30560):
```rust
type Alias = ();
use Alias::*; // This is currently allowed but shouldn't be
```
This is a [breaking-change]. Since the disallowed glob imports don't actually import anything, any breakage can be fixed by removing the offending glob import.
r? @alexcrichton
