Implement region negation to minicore and add a flag fmt_before_1_89_0

crates/test-utils/src/fixture.rs

@@ -412,44 +412,70 @@ impl MiniCore {
         }
 
         let mut active_regions = Vec::new();
+        let mut inactive_regions = Vec::new();
         let mut seen_regions = Vec::new();
         for line in lines {
             let trimmed = line.trim();
             if let Some(region) = trimmed.strip_prefix("// region:") {
+                if let Some(region) = region.strip_prefix('!') {
+                    inactive_regions.push(region);
+                    continue;
+                } else {
                     active_regions.push(region);
                     continue;
                 }
+            }
             if let Some(region) = trimmed.strip_prefix("// endregion:") {
-                let prev = active_regions.pop().unwrap();
+                let (prev, region) = if let Some(region) = region.strip_prefix('!') {
+                    (inactive_regions.pop().unwrap(), region)
+                } else {
+                    (active_regions.pop().unwrap(), region)
+                };
                 assert_eq!(prev, region, "unbalanced region pairs");
                 continue;
             }
 
-            let mut line_region = false;
-            if let Some(idx) = trimmed.find("// :") {
-                line_region = true;
+            let mut active_line_region = false;
+            let mut inactive_line_region = false;
+            if let Some(idx) = trimmed.find("// :!") {
+                inactive_line_region = true;
+                inactive_regions.push(&trimmed[idx + "// :!".len()..]);
+            } else if let Some(idx) = trimmed.find("// :") {
+                active_line_region = true;
                 active_regions.push(&trimmed[idx + "// :".len()..]);
             }
 
             let mut keep = true;
-            for &region in &active_regions {
+            for &region in active_regions.iter() {
                 assert!(!region.starts_with(' '), "region marker starts with a space: {region:?}");
                 self.assert_valid_flag(region);
                 seen_regions.push(region);
                 keep &= self.has_flag(region);
             }
+            for &region in inactive_regions.iter() {
+                assert!(!region.starts_with(' '), "region marker starts with a space: {region:?}");
+                self.assert_valid_flag(region);
+                seen_regions.push(region);
+                keep &= !self.has_flag(region);
+            }
 
             if keep {
                 buf.push_str(line);
             }
-            if line_region {
+            if active_line_region {
                 active_regions.pop().unwrap();
             }
+            if inactive_line_region {
+                inactive_regions.pop().unwrap();
+            }
         }
 
         if !active_regions.is_empty() {
             panic!("unclosed regions: {active_regions:?} Add an `endregion` comment");
         }
+        if !inactive_regions.is_empty() {
+            panic!("unclosed regions: {inactive_regions:?} Add an `endregion` comment");
+        }
 
         for flag in &self.valid_flags {
             if !seen_regions.iter().any(|it| it == flag) {

crates/test-utils/src/minicore.rs

@@ -31,6 +31,7 @@
 //!     eq: sized
 //!     error: fmt
 //!     fmt: option, result, transmute, coerce_unsized, copy, clone, derive
+//!     fmt_before_1_89_0: fmt
 //!     fn: tuple
 //!     from: sized, result
 //!     future: pin
@@ -1175,6 +1176,7 @@ pub mod fmt {
             }
         }
 
+        // region:fmt_before_1_89_0
         #[lang = "format_unsafe_arg"]
         pub struct UnsafeArg {
             _private: (),
@@ -1185,6 +1187,7 @@ pub mod fmt {
                 UnsafeArg { _private: () }
             }
         }
+        // endregion:fmt_before_1_89_0
     }
 
     #[derive(Copy, Clone)]
@@ -1204,6 +1207,7 @@ pub mod fmt {
             Arguments { pieces, fmt: None, args: &[] }
         }
 
+        // region:fmt_before_1_89_0
         pub fn new_v1_formatted(
             pieces: &'a [&'static str],
             args: &'a [rt::Argument<'a>],
@@ -1212,6 +1216,17 @@ pub mod fmt {
         ) -> Arguments<'a> {
             Arguments { pieces, fmt: Some(fmt), args }
         }
+        // endregion:fmt_before_1_89_0
+
+        // region:!fmt_before_1_89_0
+        pub unsafe fn new_v1_formatted(
+            pieces: &'a [&'static str],
+            args: &'a [rt::Argument<'a>],
+            fmt: &'a [rt::Placeholder],
+        ) -> Arguments<'a> {
+            Arguments { pieces, fmt: Some(fmt), args }
+        }
+        // endregion:!fmt_before_1_89_0
 
         pub const fn as_str(&self) -> Option<&'static str> {
             match (self.pieces, self.args) {