util: add prelude

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

rust/hw/char/pl011/src/device.rs

@@ -17,7 +17,7 @@ use migration::{
 };
 use qom::{prelude::*, ObjectImpl, Owned, ParentField, ParentInit};
 use system::{hwaddr, MemoryRegion, MemoryRegionOps, MemoryRegionOpsBuilder};
-use util::{log::Log, log_mask_ln, ResultExt};
+use util::prelude::*;
 
 use crate::registers::{self, Interrupt, RegisterOffset};
 

rust/hw/timer/hpet/src/device.rs

@@ -25,10 +25,7 @@ use system::{
     bindings::{address_space_memory, address_space_stl_le, hwaddr},
     MemoryRegion, MemoryRegionOps, MemoryRegionOpsBuilder, MEMTXATTRS_UNSPECIFIED,
 };
-use util::{
-    ensure,
-    timer::{Timer, CLOCK_VIRTUAL, NANOSECONDS_PER_SECOND},
-};
+use util::prelude::*;
 
 use crate::fw_cfg::HPETFwConfig;
 

rust/hw/timer/hpet/src/fw_cfg.rs

@@ -5,7 +5,7 @@
 use std::ptr::addr_of_mut;
 
 use common::Zeroable;
-use util::{self, ensure};
+use util::{self, prelude::*};
 
 /// Each `HPETState` represents a Event Timer Block. The v1 spec supports
 /// up to 8 blocks. QEMU only uses 1 block (in PC machine).

rust/util/meson.build

@@ -34,6 +34,7 @@ _util_rs = static_library(
       'src/error.rs',
       'src/log.rs',
       'src/module.rs',
+      'src/prelude.rs',
       'src/timer.rs',
     ],
     {'.': _util_bindings_inc_rs}

rust/util/src/lib.rs

@@ -4,6 +4,11 @@ pub mod bindings;
 pub mod error;
 pub mod log;
 pub mod module;
+
+// preserve one-item-per-"use" syntax, it is clearer
+// for prelude-like modules
+#[rustfmt::skip]
+pub mod prelude;
 pub mod timer;
 
 pub use error::{Error, Result, ResultExt};

rust/util/src/prelude.rs

@@ -0,0 +1,11 @@
+//! Essential types and traits intended for blanket imports.
+
+pub use crate::error::ResultExt;
+pub use crate::log::Log;
+pub use crate::timer::Timer;
+pub use crate::timer::CLOCK_VIRTUAL;
+pub use crate::timer::NANOSECONDS_PER_SECOND;
+
+// Re-export commonly used macros
+pub use crate::ensure;
+pub use crate::log_mask_ln;