resolve: More detailed effective visibility tracking for imports

Also drop `extern` blocks from the effective visibility table, they are nominally private and it doesn't make sense to keep them there.

src/test/ui/privacy/effective_visibilities.rs

@@ -6,7 +6,7 @@ mod outer { //~ ERROR Direct: pub(crate), Reexported: pub(crate), Reachable: pub
     pub mod inner1 { //~ ERROR Direct: pub(crate), Reexported: pub, Reachable: pub, ReachableThroughImplTrait: pub
 
         #[rustc_effective_visibility]
-        extern "C" {} //~ ERROR Direct: pub(crate), Reexported: pub, Reachable: pub, ReachableThroughImplTrait: pub
+        extern "C" {} //~ ERROR not in the table
 
         #[rustc_effective_visibility]
         pub trait PubTrait { //~ ERROR Direct: pub(crate), Reexported: pub, Reachable: pub, ReachableThroughImplTrait: pub

src/test/ui/privacy/effective_visibilities.stderr

@@ -10,7 +10,7 @@ error: Direct: pub(crate), Reexported: pub, Reachable: pub, ReachableThroughImpl
 LL |     pub mod inner1 {
    |     ^^^^^^^^^^^^^^
 
-error: Direct: pub(crate), Reexported: pub, Reachable: pub, ReachableThroughImplTrait: pub
+error: not in the table
   --> $DIR/effective_visibilities.rs:9:9
    |
 LL |         extern "C" {}

src/test/ui/privacy/effective_visibilities_glob.rs

@@ -0,0 +1,21 @@
+// Effective visibility tracking for imports is fine-grained, so `S2` is not fully exported
+// even if its parent import (`m::*`) is fully exported as a `use` item.
+
+#![feature(rustc_attrs)]
+
+mod m {
+    #[rustc_effective_visibility]
+    pub struct S1 {} //~ ERROR Direct: pub(crate), Reexported: pub, Reachable: pub, ReachableThroughImplTrait: pub
+    #[rustc_effective_visibility]
+    pub struct S2 {} //~ ERROR Direct: pub(crate), Reexported: pub(crate), Reachable: pub(crate), ReachableThroughImplTrait: pub(crate)
+}
+
+mod glob {
+    #[rustc_effective_visibility]
+    pub use crate::m::*; //~ ERROR Direct: pub(crate), Reexported: pub, Reachable: pub, ReachableThroughImplTrait: pub
+}
+
+#[rustc_effective_visibility]
+pub use glob::S1; //~ ERROR Direct: pub, Reexported: pub, Reachable: pub, ReachableThroughImplTrait: pub
+
+fn main() {}

src/test/ui/privacy/effective_visibilities_glob.stderr

@@ -0,0 +1,26 @@
+error: Direct: pub(crate), Reexported: pub, Reachable: pub, ReachableThroughImplTrait: pub
+  --> $DIR/effective_visibilities_glob.rs:8:5
+   |
+LL |     pub struct S1 {}
+   |     ^^^^^^^^^^^^^
+
+error: Direct: pub(crate), Reexported: pub(crate), Reachable: pub(crate), ReachableThroughImplTrait: pub(crate)
+  --> $DIR/effective_visibilities_glob.rs:10:5
+   |
+LL |     pub struct S2 {}
+   |     ^^^^^^^^^^^^^
+
+error: Direct: pub(crate), Reexported: pub, Reachable: pub, ReachableThroughImplTrait: pub
+  --> $DIR/effective_visibilities_glob.rs:15:13
+   |
+LL |     pub use crate::m::*;
+   |             ^^^^^^^^
+
+error: Direct: pub, Reexported: pub, Reachable: pub, ReachableThroughImplTrait: pub
+  --> $DIR/effective_visibilities_glob.rs:19:9
+   |
+LL | pub use glob::S1;
+   |         ^^^^^^^^
+
+error: aborting due to 4 previous errors
+