Auto merge of rust-lang#114962 - darklyspaced:debug, r=est31

adds a column number to `dbg!()`

this would be very nice to have for a few reasons:
1. the rfc, when deciding not to add column numbers to macro, failed to acknowledge any potential ambiguous cases -- such as the one provided in rust-lang#114910 -- which do exist
2. would be able to consistently and easily jump directly to the `dbg!()` regardless of the sutation
3. takes up, at a maximum, 3 characters of _horizontal_ screen space

fixes rust-lang#114910

Author: bors

std/src/macros.rs

@@ -355,15 +355,15 @@ macro_rules! dbg {
     // `$val` expression could be a block (`{ .. }`), in which case the `eprintln!`
     // will be malformed.
     () => {
-        $crate::eprintln!("[{}:{}]", $crate::file!(), $crate::line!())
+        $crate::eprintln!("[{}:{}:{}]", $crate::file!(), $crate::line!(), $crate::column!())
     };
     ($val:expr $(,)?) => {
         // Use of `match` here is intentional because it affects the lifetimes
         // of temporaries - https://stackoverflow.com/a/48732525/1063961
         match $val {
             tmp => {
-                $crate::eprintln!("[{}:{}] {} = {:#?}",
-                    $crate::file!(), $crate::line!(), $crate::stringify!($val), &tmp);
+                $crate::eprintln!("[{}:{}:{}] {} = {:#?}",
+                    $crate::file!(), $crate::line!(), $crate::column!(), $crate::stringify!($val), &tmp);
                 tmp
             }
         }