added `try_find_description` to distinguish no desc from invalid code

3 files changed, 29 insertions, 9 deletions

diff --git a/src/librustc_errors/json.rs b/src/librustc_errors/json.rs
index df73785b8f6..0767b8dda9b 100644
--- a/src/librustc_errors/json.rs
+++ b/src/librustc_errors/json.rs
@@ -419,10 +419,10 @@ impl DiagnosticCode {
                 DiagnosticId::Error(s) => s,
                 DiagnosticId::Lint(s) => s,
             };
-            let explanation =
-                je.registry.as_ref().and_then(|registry| registry.find_description(&s));
+            let je_result =
+                je.registry.as_ref().map(|registry| registry.try_find_description(&s)).unwrap();
 
-            DiagnosticCode { code: s, explanation }
+            DiagnosticCode { code: s, explanation: je_result.unwrap_or(None) }
         })
     }
 }
diff --git a/src/librustc_errors/lib.rs b/src/librustc_errors/lib.rs
index 1a0fe343521..bc943f2c09c 100644
--- a/src/librustc_errors/lib.rs
+++ b/src/librustc_errors/lib.rs
@@ -786,8 +786,12 @@ impl HandlerInner {
                 .emitted_diagnostic_codes
                 .iter()
                 .filter_map(|x| match &x {
-                    DiagnosticId::Error(s) if registry.find_description(s).is_some() => {
-                        Some(s.clone())
+                    DiagnosticId::Error(s) => {
+                        if let Ok(Some(_explanation)) = registry.try_find_description(s) {
+                            Some(s.clone())
+                        } else {
+                            None
+                        }
                     }
                     _ => None,
                 })
diff --git a/src/librustc_errors/registry.rs b/src/librustc_errors/registry.rs
index 771542cb06f..c92a9d04775 100644
--- a/src/librustc_errors/registry.rs
+++ b/src/librustc_errors/registry.rs
@@ -1,16 +1,32 @@
 use rustc_data_structures::fx::FxHashMap;
 
+#[derive(Debug)]
+pub struct InvalidErrorCode;
+
 #[derive(Clone)]
 pub struct Registry {
-    descriptions: FxHashMap<&'static str, &'static str>,
+    long_descriptions: FxHashMap<&'static str, Option<&'static str>>,
 }
 
 impl Registry {
-    pub fn new(descriptions: &[(&'static str, &'static str)]) -> Registry {
-        Registry { descriptions: descriptions.iter().cloned().collect() }
+    pub fn new(long_descriptions: &[(&'static str, Option<&'static str>)]) -> Registry {
+        Registry { long_descriptions: long_descriptions.iter().cloned().collect() }
     }
 
+    /// This will panic if an invalid error code is passed in
     pub fn find_description(&self, code: &str) -> Option<&'static str> {
-        self.descriptions.get(code).cloned()
+        self.try_find_description(code).unwrap()
+    }
+    /// Returns `InvalidErrorCode` if the code requested does not exist in the
+    /// registry. Otherwise, returns an `Option` where `None` means the error
+    /// code is valid but has no extended information.
+    pub fn try_find_description(
+        &self,
+        code: &str,
+    ) -> Result<Option<&'static str>, InvalidErrorCode> {
+        if !self.long_descriptions.contains_key(code) {
+            return Err(InvalidErrorCode);
+        }
+        Ok(self.long_descriptions.get(code).unwrap().clone())
     }
 }