1 files changed, 139 insertions, 0 deletions
diff --git a/third_party/rust/regex-automata/src/hybrid/error.rs b/third_party/rust/regex-automata/src/hybrid/error.rs
new file mode 100644
index 0000000000..604daf3c38
--- /dev/null
+++ b/third_party/rust/regex-automata/src/hybrid/error.rs
@@ -0,0 +1,139 @@
+use crate::{hybrid::id::LazyStateIDError, nfa};
+
+/// An error that occurs when initial construction of a lazy DFA fails.
+///
+/// A build error can occur when insufficient cache capacity is configured or
+/// if something about the NFA is unsupported. (For example, if one attempts
+/// to build a lazy DFA without heuristic Unicode support but with an NFA that
+/// contains a Unicode word boundary.)
+///
+/// This error does not provide many introspection capabilities. There are
+/// generally only two things you can do with it:
+///
+/// * Obtain a human readable message via its `std::fmt::Display` impl.
+/// * Access an underlying
+/// [`nfa::thompson::BuildError`](crate::nfa::thompson::BuildError)
+/// type from its `source` method via the `std::error::Error` trait. This error
+/// only occurs when using convenience routines for building a lazy DFA
+/// directly from a pattern string.
+///
+/// When the `std` feature is enabled, this implements the `std::error::Error`
+/// trait.
+#[derive(Clone, Debug)]
+pub struct BuildError {
+    kind: BuildErrorKind,
+}
+
+#[derive(Clone, Debug)]
+enum BuildErrorKind {
+    NFA(nfa::thompson::BuildError),
+    InsufficientCacheCapacity { minimum: usize, given: usize },
+    InsufficientStateIDCapacity { err: LazyStateIDError },
+    Unsupported(&'static str),
+}
+
+impl BuildError {
+    pub(crate) fn nfa(err: nfa::thompson::BuildError) -> BuildError {
+        BuildError { kind: BuildErrorKind::NFA(err) }
+    }
+
+    pub(crate) fn insufficient_cache_capacity(
+        minimum: usize,
+        given: usize,
+    ) -> BuildError {
+        BuildError {
+            kind: BuildErrorKind::InsufficientCacheCapacity { minimum, given },
+        }
+    }
+
+    pub(crate) fn insufficient_state_id_capacity(
+        err: LazyStateIDError,
+    ) -> BuildError {
+        BuildError {
+            kind: BuildErrorKind::InsufficientStateIDCapacity { err },
+        }
+    }
+
+    pub(crate) fn unsupported_dfa_word_boundary_unicode() -> BuildError {
+        let msg = "cannot build lazy DFAs for regexes with Unicode word \
+                   boundaries; switch to ASCII word boundaries, or \
+                   heuristically enable Unicode word boundaries or use a \
+                   different regex engine";
+        BuildError { kind: BuildErrorKind::Unsupported(msg) }
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for BuildError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        match self.kind {
+            BuildErrorKind::NFA(ref err) => Some(err),
+            _ => None,
+        }
+    }
+}
+
+impl core::fmt::Display for BuildError {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self.kind {
+            BuildErrorKind::NFA(_) => write!(f, "error building NFA"),
+            BuildErrorKind::InsufficientCacheCapacity { minimum, given } => {
+                write!(
+                    f,
+                    "given cache capacity ({}) is smaller than \
+                     minimum required ({})",
+                    given, minimum,
+                )
+            }
+            BuildErrorKind::InsufficientStateIDCapacity { ref err } => {
+                err.fmt(f)
+            }
+            BuildErrorKind::Unsupported(ref msg) => {
+                write!(f, "unsupported regex feature for DFAs: {}", msg)
+            }
+        }
+    }
+}
+
+/// An error that occurs when cache usage has become inefficient.
+///
+/// One of the weaknesses of a lazy DFA is that it may need to clear its
+/// cache repeatedly if it's not big enough. If this happens too much, then it
+/// can slow searching down significantly. A mitigation to this is to use
+/// heuristics to detect whether the cache is being used efficiently or not.
+/// If not, then a lazy DFA can return a `CacheError`.
+///
+/// The default configuration of a lazy DFA in this crate is
+/// set such that a `CacheError` will never occur. Instead,
+/// callers must opt into this behavior with settings like
+/// [`dfa::Config::minimum_cache_clear_count`](crate::hybrid::dfa::Config::minimum_cache_clear_count)
+/// and
+/// [`dfa::Config::minimum_bytes_per_state`](crate::hybrid::dfa::Config::minimum_bytes_per_state).
+///
+/// When the `std` feature is enabled, this implements the `std::error::Error`
+/// trait.
+#[derive(Clone, Debug)]
+pub struct CacheError(());
+
+impl CacheError {
+    pub(crate) fn too_many_cache_clears() -> CacheError {
+        CacheError(())
+    }
+
+    pub(crate) fn bad_efficiency() -> CacheError {
+        CacheError(())
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for CacheError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        None
+    }
+}
+
+impl core::fmt::Display for CacheError {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        write!(f, "lazy DFA cache has been cleared too many times")
+    }
+}