From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Thu, 4 Mar 2021 21:02:05 +0000 (+0000)
Subject: provide dbgc!, version of dbg! which prints compactly
X-Git-Tag: otter-0.4.0~246
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=commitdiff_plain;h=e2f7cf3e649b94eb39e1ee0ad54e0317040d12b9;p=otter.git

provide dbgc!, version of dbg! which prints compactly

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---

diff --git a/src/prelude.rs b/src/prelude.rs
index 17d4d232..7baa8932 100644
--- a/src/prelude.rs
+++ b/src/prelude.rs
@@ -95,6 +95,7 @@ pub use otter_base::zcoord::{self, ZCoord};
 pub use otter_base::misc as base_misc;
 pub use base_misc::default;
 
+pub use crate::dbgc;
 pub use crate::{deref_to_field, deref_to_field_mut};
 pub use crate::ensure_eq;
 pub use crate::from_instance_lock_error;
diff --git a/src/utils.rs b/src/utils.rs
index a062eb97..f08b4425 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -352,3 +352,28 @@ impl<T,U,E,F> IteratorExt<U,E,F> for T where
       })
   }
 }
+
+#[macro_export]
+macro_rules! dbgc {
+    // NOTE: We cannot use `concat!` to make a static string as a format argument
+    // of `eprintln!` because `file!` could contain a `{` or
+    // `$val` expression could be a block (`{ .. }`), in which case the `eprintln!`
+    // will be malformed.
+    () => {
+        std::eprintln!("[{}:{}]", std::file!(), std::line!());
+    };
+    ($val:expr $(,)?) => {
+        // Use of `match` here is intentional because it affects the lifetimes
+        // of temporaries - https://stackoverflow.com/a/48732525/1063961
+        match $val {
+            tmp => {
+                std::eprintln!("[{}:{}] {} = {:?}",
+                    std::file!(), std::line!(), std::stringify!($val), &tmp);
+                tmp
+            }
+        }
+    };
+    ($($val:expr),+ $(,)?) => {
+        ($(std::dbg!($val)),+,)
+    };
+}