errors: IntoDiagnosticArg for io::Error/paths

Add impls of `IntoDiagnosticArg` for `std::io::Error`, `std::path::Path`
and `std::path::PathBuf`.

Signed-off-by: David Wood <david.wood@huawei.com>

compiler/rustc_errors/src/diagnostic.rs

@@ -13,6 +13,7 @@ use rustc_span::{edition::Edition, Span, DUMMY_SP};
 use std::borrow::Cow;
 use std::fmt;
 use std::hash::{Hash, Hasher};
+use std::path::{Path, PathBuf};
 
 /// Error type for `Diagnostic`'s `suggestions` field, indicating that
 /// `.disable_suggestions()` was called on the `Diagnostic`.
@@ -83,6 +84,7 @@ into_diagnostic_arg_using_display!(
     u64,
     i128,
     u128,
+    std::io::Error,
     std::num::NonZeroU32,
     hir::Target,
     Edition,
@@ -124,6 +126,18 @@ impl IntoDiagnosticArg for String {
     }
 }
 
+impl<'a> IntoDiagnosticArg for &'a Path {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        DiagnosticArgValue::Str(Cow::Owned(self.display().to_string()))
+    }
+}
+
+impl IntoDiagnosticArg for PathBuf {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        DiagnosticArgValue::Str(Cow::Owned(self.display().to_string()))
+    }
+}
+
 impl IntoDiagnosticArg for usize {
     fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
         DiagnosticArgValue::Number(self)