Support allocation failures when interperting MIR

Note that this breaks Miri.

Closes #79601

compiler/rustc_mir/src/const_eval/eval_queries.rs

@@ -48,7 +48,7 @@ fn eval_body_using_ecx<'mir, 'tcx>(
     );
     let layout = ecx.layout_of(body.return_ty().subst(tcx, cid.instance.substs))?;
     assert!(!layout.is_unsized());
-    let ret = ecx.allocate(layout, MemoryKind::Stack);
+    let ret = ecx.allocate(layout, MemoryKind::Stack)?;
 
     let name =
         with_no_trimmed_paths(|| ty::tls::with(|tcx| tcx.def_path_str(cid.instance.def_id())));

compiler/rustc_mir/src/const_eval/machine.rs

@@ -306,7 +306,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
                     Size::from_bytes(size as u64),
                     align,
                     interpret::MemoryKind::Machine(MemoryKind::Heap),
-                );
+                )?;
                 ecx.write_scalar(Scalar::Ptr(ptr), dest)?;
             }
             _ => {

compiler/rustc_mir/src/const_eval/mod.rs

@@ -31,7 +31,11 @@ pub(crate) fn const_caller_location(
     trace!("const_caller_location: {}:{}:{}", file, line, col);
     let mut ecx = mk_eval_cx(tcx, DUMMY_SP, ty::ParamEnv::reveal_all(), false);
 
-    let loc_place = ecx.alloc_caller_location(file, line, col);
+    // This can fail if rustc runs out of memory right here. Trying to emit an error would be
+    // pointless, since that would require allocating more memory than a Location.
+    let loc_place = ecx
+        .alloc_caller_location(file, line, col)
+        .expect("not enough memory to allocate location?");
     if intern_const_alloc_recursive(&mut ecx, InternKind::Constant, &loc_place).is_err() {
         bug!("intern_const_alloc_recursive should not error in this case")
     }