fix(naga): use Diagnostic from inner in valid. err. presentation

For some reason, the implementation of `Display` for
`ShaderError<WithSpan<ValidationError>>>` is building its own
`Diagnostic` with _only_ the labels populated: no messages or notes.
I don't know why this is, but it seems to have a strict subset of the
information already present in the private implementation of
`WithSpan::diagnostic`.

Fix this by exposing `WithSpan::diagnostic` as `pub(crate)`, and
re-using its output in `impl Display for
ShaderError<WithSpan<ValidationError>>>`.

CHANGELOG.md

@@ -86,6 +86,7 @@ By @bradwerth [#6216](https://github.com/gfx-rs/wgpu/pull/6216).
 - Implemented `const_assert` in WGSL. By @sagudev in [#6198](https://github.com/gfx-rs/wgpu/pull/6198).
 - Support polyfilling `inverse` in WGSL. By @chyyran in [#6385](https://github.com/gfx-rs/wgpu/pull/6385).
 - Add an internal skeleton for parsing `requires`, `enable`, and `diagnostic` directives that don't yet do anything besides emit nicer errors. By @ErichDonGubler in [#6352](https://github.com/gfx-rs/wgpu/pull/6352).
+- Include error chain information as a message and notes in shader compilation messages. By @ErichDonGubler in [#6436](https://github.com/gfx-rs/wgpu/pull/6436).
 
 #### General
 

naga/src/error.rs

@@ -34,28 +34,14 @@ impl fmt::Display for ShaderError<crate::front::spv::Error> {
 }
 impl fmt::Display for ShaderError<crate::WithSpan<crate::valid::ValidationError>> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        use codespan_reporting::{
-            diagnostic::{Diagnostic, Label},
-            files::SimpleFile,
-            term,
-        };
+        use codespan_reporting::{files::SimpleFile, term};
 
         let label = self.label.as_deref().unwrap_or_default();
         let files = SimpleFile::new(label, &self.source);
         let config = term::Config::default();
         let mut writer = termcolor::NoColor::new(Vec::new());
-
-        let diagnostic = Diagnostic::error().with_labels(
-            self.inner
-                .spans()
-                .map(|&(span, ref desc)| {
-                    Label::primary((), span.to_range().unwrap()).with_message(desc.to_owned())
-                })
-                .collect(),
-        );
-
-        term::emit(&mut writer, &config, &files, &diagnostic).expect("cannot write error");
-
+        term::emit(&mut writer, &config, &files, &self.inner.diagnostic())
+            .expect("cannot write error");
         write!(
             f,
             "\nShader validation {}",

naga/src/span.rs

@@ -239,7 +239,7 @@ impl<E> WithSpan<E> {
         Some(self.spans[0].0.location(source))
     }
 
-    fn diagnostic(&self) -> codespan_reporting::diagnostic::Diagnostic<()>
+    pub(crate) fn diagnostic(&self) -> codespan_reporting::diagnostic::Diagnostic<()>
     where
         E: Error,
     {