Auto merge of #101986 - WaffleLapkin:move_lint_note_to_the_bottom, r=estebank

Move lint level source explanation to the bottom

So, uhhhhh

r? `@estebank`

## User-facing change

"note: `#[warn(...)]` on by default" and such are moved to the bottom of the diagnostic:
```diff
-   = note: `#[warn(unsupported_calling_conventions)]` on by default
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #87678 <https://github.com/rust-lang/rust/issues/87678>
+   = note: `#[warn(unsupported_calling_conventions)]` on by default
```

Why warning is enabled is the least important thing, so it shouldn't be the first note the user reads, IMO.

## Developer-facing change

`struct_span_lint` and similar methods have a different signature.

Before: `..., impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>)`
After: `..., impl Into<DiagnosticMessage>, impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>) -> &'b mut DiagnosticBuilder<'a, ()>`

The reason for this is that `struct_span_lint` needs to edit the diagnostic _after_ `decorate` closure is called. This also makes lint code a little bit nicer in my opinion.

Another option is to use `impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>) -> DiagnosticBuilder<'a, ()>` altough I don't _really_ see reasons to do `let lint = lint.build(message)` everywhere.

## Subtle problem

By moving the message outside of the closure (that may not be called if the lint is disabled) `format!(...)` is executed earlier, possibly formatting `Ty` which may call a query that trims paths that crashes the compiler if there were no warnings...

I don't think it's that big of a deal, considering that we move from `format!(...)` to `fluent` (which is lazy by-default) anyway, however this required adding a workaround which is unfortunate.

## P.S.

I'm sorry, I do not how to make this PR smaller/easier to review. Changes to the lint API affect SO MUCH 😢

1 files changed, 49 insertions, 45 deletions

diff --git a/compiler/rustc_lint/src/hidden_unicode_codepoints.rs b/compiler/rustc_lint/src/hidden_unicode_codepoints.rs
index 8f22221324a..42557068bd3 100644
--- a/compiler/rustc_lint/src/hidden_unicode_codepoints.rs
+++ b/compiler/rustc_lint/src/hidden_unicode_codepoints.rs
@@ -60,52 +60,56 @@ impl HiddenUnicodeCodepoints {
             })
             .collect();
 
-        cx.struct_span_lint(TEXT_DIRECTION_CODEPOINT_IN_LITERAL, span, |lint| {
-            let mut err = lint.build(fluent::lint::hidden_unicode_codepoints);
-            err.set_arg("label", label);
-            err.set_arg("count", spans.len());
-            err.span_label(span, fluent::lint::label);
-            err.note(fluent::lint::note);
-            if point_at_inner_spans {
-                for (c, span) in &spans {
-                    err.span_label(*span, format!("{:?}", c));
+        cx.struct_span_lint(
+            TEXT_DIRECTION_CODEPOINT_IN_LITERAL,
+            span,
+            fluent::lint::hidden_unicode_codepoints,
+            |lint| {
+                lint.set_arg("label", label);
+                lint.set_arg("count", spans.len());
+                lint.span_label(span, fluent::lint::label);
+                lint.note(fluent::lint::note);
+                if point_at_inner_spans {
+                    for (c, span) in &spans {
+                        lint.span_label(*span, format!("{:?}", c));
+                    }
                 }
-            }
-            if point_at_inner_spans && !spans.is_empty() {
-                err.multipart_suggestion_with_style(
-                    fluent::lint::suggestion_remove,
-                    spans.iter().map(|(_, span)| (*span, "".to_string())).collect(),
-                    Applicability::MachineApplicable,
-                    SuggestionStyle::HideCodeAlways,
-                );
-                err.multipart_suggestion(
-                    fluent::lint::suggestion_escape,
-                    spans
-                        .into_iter()
-                        .map(|(c, span)| {
-                            let c = format!("{:?}", c);
-                            (span, c[1..c.len() - 1].to_string())
-                        })
-                        .collect(),
-                    Applicability::MachineApplicable,
-                );
-            } else {
-                // FIXME: in other suggestions we've reversed the inner spans of doc comments. We
-                // should do the same here to provide the same good suggestions as we do for
-                // literals above.
-                err.set_arg(
-                    "escaped",
-                    spans
-                        .into_iter()
-                        .map(|(c, _)| format!("{:?}", c))
-                        .collect::<Vec<String>>()
-                        .join(", "),
-                );
-                err.note(fluent::lint::suggestion_remove);
-                err.note(fluent::lint::no_suggestion_note_escape);
-            }
-            err.emit();
-        });
+                if point_at_inner_spans && !spans.is_empty() {
+                    lint.multipart_suggestion_with_style(
+                        fluent::lint::suggestion_remove,
+                        spans.iter().map(|(_, span)| (*span, "".to_string())).collect(),
+                        Applicability::MachineApplicable,
+                        SuggestionStyle::HideCodeAlways,
+                    );
+                    lint.multipart_suggestion(
+                        fluent::lint::suggestion_escape,
+                        spans
+                            .into_iter()
+                            .map(|(c, span)| {
+                                let c = format!("{:?}", c);
+                                (span, c[1..c.len() - 1].to_string())
+                            })
+                            .collect(),
+                        Applicability::MachineApplicable,
+                    );
+                } else {
+                    // FIXME: in other suggestions we've reversed the inner spans of doc comments. We
+                    // should do the same here to provide the same good suggestions as we do for
+                    // literals above.
+                    lint.set_arg(
+                        "escaped",
+                        spans
+                            .into_iter()
+                            .map(|(c, _)| format!("{:?}", c))
+                            .collect::<Vec<String>>()
+                            .join(", "),
+                    );
+                    lint.note(fluent::lint::suggestion_remove);
+                    lint.note(fluent::lint::no_suggestion_note_escape);
+                }
+                lint
+            },
+        );
     }
 }
 impl EarlyLintPass for HiddenUnicodeCodepoints {