Fixed bug with miri const evaluation where allocation is recursively borrowed.

Author: Alexander Regueiro

src/librustc_mir/interpret/memory.rs

@@ -310,7 +310,8 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
                 Some(alloc) => Ok(alloc),
                 None => {
                     // static alloc?
-                    match self.tcx.alloc_map.lock().get(id) {
+                    let alloc = self.tcx.alloc_map.lock().get(id);
+                    match alloc {
                         Some(AllocType::Memory(mem)) => Ok(mem),
                         Some(AllocType::Function(..)) => {
                             Err(EvalErrorKind::DerefFunctionPointer.into())

src/test/compile-fail/issue-28324.rs

@@ -16,5 +16,6 @@ extern {
 
 pub static BAZ: u32 = *&error_message_count;
 //~^ ERROR constant evaluation error
+//~| tried to read foreign (extern) static
 
 fn main() {}

src/test/compile-fail/auxiliary/pub_static_array.rs renamed to src/test/run-pass/auxiliary/pub_static_array.rs

@@ -15,13 +15,7 @@ extern crate pub_static_array as array;
 use array::ARRAY;
 
 static X: &'static u8 = &ARRAY[0];
-//~^ ERROR: cannot refer to the interior of another static, use a constant
-
 static Y: &'static u8 = &(&ARRAY)[0];
-//~^ ERROR: cannot refer to the interior of another static, use a constant
-
 static Z: u8 = (&ARRAY)[0];
-//~^ ERROR: cannot refer to the interior of another static, use a constant
-//~^^ ERROR: cannot refer to other statics by value
 
 pub fn main() {}