[PATCH v2 2/3] rust: kunit: use `line!()` inside `kunit_assert!`

[Gary Guo <gary@garyguo.net>]

The `diff` parameter is needed currently because doctests want to override
the line number. Simplify it by changing it to use `line!()`. Have doctests
override `line!()` macro to achieve the current behavior.

A few current doctests (or their invoked macros) require `line!()` to
expand to literal; they're updated to use `::core::line!()` instead.

Reviewed-by: David Gow <david@davidgow.net>
Signed-off-by: Gary Guo <gary@garyguo.net>
---
 rust/kernel/kunit.rs        |  8 ++++----
 rust/kernel/str.rs          |  2 +-
 rust/macros/kunit.rs        |  4 ++--
 scripts/rustdoc_test_gen.rs | 16 ++++++++++++----
 4 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
index 12084873b51e..27b109923407 100644
--- a/rust/kernel/kunit.rs
+++ b/rust/kernel/kunit.rs
@@ -58,7 +58,7 @@ pub fn info(args: fmt::Arguments<'_>) {
 #[doc(hidden)]
 #[macro_export]
 macro_rules! kunit_assert {
-    ($name:literal, $diff:expr, $condition:expr $(,)?) => {
+    ($name:literal, $condition:expr $(,)?) => {
         'out: {
             // Do nothing if the condition is `true`.
             if $condition {
@@ -67,7 +67,7 @@ macro_rules! kunit_assert {
 
             // Use `file!()` instead of `::core::file!()` here so it can be overridden.
             static FILE: &'static $crate::str::CStr = $crate::c_str!(file!());
-            static LINE: i32 = ::core::line!() as i32 - $diff;
+            static LINE: i32 = line!() as i32;
             static CONDITION: &'static $crate::str::CStr = $crate::c_str!(stringify!($condition));
 
             // SAFETY: FFI call without safety requirements.
@@ -165,10 +165,10 @@ unsafe impl Sync for UnaryAssert {}
 #[doc(hidden)]
 #[macro_export]
 macro_rules! kunit_assert_eq {
-    ($name:literal, $diff:expr, $left:expr, $right:expr $(,)?) => {{
+    ($name:literal, $left:expr, $right:expr $(,)?) => {{
         // For the moment, we just forward to the expression assert because, for binary asserts,
         // KUnit supports only a few types (e.g. integers).
-        $crate::kunit_assert!($name, $diff, $left == $right);
+        $crate::kunit_assert!($name, $left == $right);
     }};
 }
 
diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
index b3caa9a1c898..644b4279a116 100644
--- a/rust/kernel/str.rs
+++ b/rust/kernel/str.rs
@@ -411,7 +411,7 @@ fn as_ref(&self) -> &BStr {
 /// const BAD: &CStr = c_str!("literal");
 ///
 /// // `c_str!` is still needed for static non-literal C strings.
-/// const GOOD: &CStr = c_str!(concat!(file!(), ":", line!(), ": My CStr!"));
+/// const GOOD: &CStr = c_str!(concat!(file!(), ":", ::core::line!(), ": My CStr!"));
 /// ```
 #[macro_export]
 macro_rules! c_str {
diff --git a/rust/macros/kunit.rs b/rust/macros/kunit.rs
index 936eff014870..e9152b9d51f9 100644
--- a/rust/macros/kunit.rs
+++ b/rust/macros/kunit.rs
@@ -113,7 +113,7 @@ pub(crate) fn kunit_tests(test_suite: Ident, mut module: ItemMod) -> Result<Toke
             #[allow(unused)]
             macro_rules! assert {
                 ($cond:expr $(,)?) => {{
-                    kernel::kunit_assert!(#test_str, 0, $cond);
+                    kernel::kunit_assert!(#test_str, $cond);
                 }}
             }
         });
@@ -121,7 +121,7 @@ macro_rules! assert {
             #[allow(unused)]
             macro_rules! assert_eq {
                 ($left:expr, $right:expr $(,)?) => {{
-                    kernel::kunit_assert_eq!(#test_str, 0, $left, $right);
+                    kernel::kunit_assert_eq!(#test_str, $left, $right);
                 }}
             }
         });
diff --git a/scripts/rustdoc_test_gen.rs b/scripts/rustdoc_test_gen.rs
index bb57745ec339..bb870f83dde2 100644
--- a/scripts/rustdoc_test_gen.rs
+++ b/scripts/rustdoc_test_gen.rs
@@ -176,18 +176,26 @@ fn main() {
             r#"/// Generated `{name}` KUnit test case from a Rust documentation test.
 #[no_mangle]
 pub extern "C" fn {kunit_name}(__kunit_test: *mut ::kernel::bindings::kunit) {{
-    /// Overrides the usual [`file!`] macro with one that expands to the real path.
+    // Overrides the usual [`file!`] macro with one that expands to the real path.
     #[allow(unused)]
     macro_rules! file {{
         () => {{ "{real_path}" }}
     }}
 
+    // Overrides the usual [`line!`] macro with one that expands to the real line number.
+    #[allow(unused)]
+    macro_rules! line {{
+        // NOTE: This does not expand to a literal, but a constant expression.
+        // Therefore code that depends on `line!()` being overrideable needs special adjustment.
+        () => {{ const {{ ::core::line!() - __DOCTEST_ANCHOR + {line} }} }}
+    }}
+
     /// Overrides the usual [`assert!`] macro with one that calls KUnit instead.
     #[allow(unused)]
     macro_rules! assert {{
         ($cond:expr $(,)?) => {{{{
             ::kernel::kunit_assert!(
-                "{kunit_name}", __DOCTEST_ANCHOR - {line}, $cond
+                "{kunit_name}", $cond
             );
         }}}}
     }}
@@ -197,7 +205,7 @@ macro_rules! assert {{
     macro_rules! assert_eq {{
         ($left:expr, $right:expr $(,)?) => {{{{
             ::kernel::kunit_assert_eq!(
-                "{kunit_name}", __DOCTEST_ANCHOR - {line}, $left, $right
+                "{kunit_name}", $left, $right
             );
         }}}}
     }}
@@ -219,7 +227,7 @@ macro_rules! assert_eq {{
 
     /// The anchor where the test code body starts.
     #[allow(unused)]
-    static __DOCTEST_ANCHOR: i32 = ::core::line!() as i32 + {body_offset} + 2;
+    static __DOCTEST_ANCHOR: u32 = ::core::line!() + {body_offset} + 2;
     {{
         #![allow(unreachable_pub, clippy::disallowed_names)]
         {body}

-- 
2.54.0