Reachable statics have reachable initializers

Static initializer can read other statics. Initializers are evaluated at
compile time, and so their content could become inlined into another
crate. Ensure that initializers of reachable statics are also reachable.

Previously, when an item incorrectly considered to be unreachable was
reached from another crate an attempt would be made to codegen it. The
attempt could fail with an ICE (in the case MIR wasn't available to do
so) in some circumstances the attempt could also succeed resulting in
a local codegen of non-local items, including static ones.

compiler/rustc_passes/src/reachable.rs

@@ -250,7 +250,7 @@ impl<'tcx> ReachableContext<'tcx> {
                     // Reachable constants will be inlined into other crates
                     // unconditionally, so we need to make sure that their
                     // contents are also reachable.
-                    hir::ItemKind::Const(_, init) => {
+                    hir::ItemKind::Const(_, init) | hir::ItemKind::Static(_, _, init) => {
                         self.visit_nested_body(init);
                     }
 
@@ -261,7 +261,6 @@ impl<'tcx> ReachableContext<'tcx> {
                     | hir::ItemKind::Use(..)
                     | hir::ItemKind::OpaqueTy(..)
                     | hir::ItemKind::TyAlias(..)
-                    | hir::ItemKind::Static(..)
                     | hir::ItemKind::Mod(..)
                     | hir::ItemKind::ForeignMod { .. }
                     | hir::ItemKind::Impl { .. }

src/test/codegen/external-no-mangle-statics.rs

@@ -58,7 +58,6 @@ const HIDDEN: () = {
     pub static mut L: u8 = 0;
 };
 
-// The surrounding item should not accidentally become external
 fn x() {
     // CHECK: @M = local_unnamed_addr constant
     #[no_mangle]
@@ -76,6 +75,3 @@ fn x() {
     #[no_mangle]
     pub static mut P: u8 = 0;
 }
-// CHECK-LABEL: ; external_no_mangle_statics::x
-// CHECK-NEXT: ; Function Attrs:
-// CHECK-NEXT: define internal

src/test/ui/cross-crate/auxiliary/static_init_aux.rs

@@ -0,0 +1,10 @@
+pub static V: &u32 = &X;
+pub static F: fn() = f;
+
+static X: u32 = 42;
+
+pub fn v() -> *const u32 {
+    V
+}
+
+fn f() {}

src/test/ui/cross-crate/static-init.rs

@@ -0,0 +1,15 @@
+// run-pass
+// aux-build:static_init_aux.rs
+extern crate static_init_aux as aux;
+
+static V: &u32 = aux::V;
+static F: fn() = aux::F;
+
+fn v() -> *const u32 {
+    V
+}
+
+fn main() {
+    assert_eq!(aux::v(), crate::v());
+    F();
+}