added error handle for error code > 9999

Author: Kivooeo

compiler/rustc_driver_impl/src/lib.rs

@@ -463,6 +463,7 @@ fn handle_explain(early_dcx: &EarlyDiagCtxt, registry: Registry, code: &str, col
     // Allow "E0123" or "0123" form.
     let upper_cased_code = code.to_ascii_uppercase();
     if let Ok(code) = upper_cased_code.strip_prefix('E').unwrap_or(&upper_cased_code).parse::<u32>()
+        && code <= ErrCode::MAX_AS_U32
         && let Ok(description) = registry.try_find_description(ErrCode::from_u32(code))
     {
         let mut is_in_code_block = false;

tests/ui/explain.rs renamed to tests/ui/explain/basic.rs

@@ -0,0 +1,4 @@
+// Check that we don't crash on error codes exceeding our internal limit.
+// issue: <https://github.com/rust-lang/rust/issues/140647>
+//@ compile-flags: --explain E10000
+//~? ERROR: E10000 is not a valid error code

tests/ui/explain.stdout renamed to tests/ui/explain/basic.stdout

@@ -0,0 +1,2 @@
+error: E10000 is not a valid error code
+