Rollup merge of #98267 - compiler-errors:suggest-wildcard-arm, r=oli-obk

Don't omit comma when suggesting wildcard arm after macro expr

* Also adds `Span::eq_ctxt` to consolidate the various usages of `span.ctxt() == other.ctxt()`
* Also fixes an unhygenic usage of spans which caused the suggestion to render weirdly when we had one arm match in a macro
* Also always suggests a comma (i.e. even after a block) if we're rendering a wildcard arm in a single-line match (looks prettier 🌹)

Fixes #94866

compiler/rustc_middle/src/mir/spanview.rs

@@ -667,7 +667,7 @@ fn trim_span_hi(span: Span, to_pos: BytePos) -> Span {
 fn fn_span<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> Span {
     let fn_decl_span = tcx.def_span(def_id);
     if let Some(body_span) = hir_body(tcx, def_id).map(|hir_body| hir_body.value.span) {
-        if fn_decl_span.ctxt() == body_span.ctxt() { fn_decl_span.to(body_span) } else { body_span }
+        if fn_decl_span.eq_ctxt(body_span) { fn_decl_span.to(body_span) } else { body_span }
     } else {
         fn_decl_span
     }

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -803,7 +803,7 @@ fn non_exhaustive_match<'p, 'tcx>(
     let mut suggestion = None;
     let sm = cx.tcx.sess.source_map();
     match arms {
-        [] if sp.ctxt() == expr_span.ctxt() => {
+        [] if sp.eq_ctxt(expr_span) => {
             // Get the span for the empty match body `{}`.
             let (indentation, more) = if let Some(snippet) = sm.indentation_before(sp) {
                 (format!("\n{}", snippet), "    ")
@@ -821,24 +821,36 @@ fn non_exhaustive_match<'p, 'tcx>(
             ));
         }
         [only] => {
-            let pre_indentation = if let (Some(snippet), true) = (
-                sm.indentation_before(only.span),
-                sm.is_multiline(sp.shrink_to_hi().with_hi(only.span.lo())),
-            ) {
-                format!("\n{}", snippet)
+            let (pre_indentation, is_multiline) = if let Some(snippet) = sm.indentation_before(only.span)
+                && let Ok(with_trailing) = sm.span_extend_while(only.span, |c| c.is_whitespace() || c == ',')
+                && sm.is_multiline(with_trailing)
+            {
+                (format!("\n{}", snippet), true)
+            } else {
+                (" ".to_string(), false)
+            };
+            let comma = if matches!(only.body.kind, hir::ExprKind::Block(..))
+                && only.span.eq_ctxt(only.body.span)
+                && is_multiline
+            {
+                ""
             } else {
-                " ".to_string()
+                ","
             };
-            let comma = if matches!(only.body.kind, hir::ExprKind::Block(..)) { "" } else { "," };
             suggestion = Some((
                 only.span.shrink_to_hi(),
                 format!("{}{}{} => todo!()", comma, pre_indentation, pattern),
             ));
         }
-        [.., prev, last] if prev.span.ctxt() == last.span.ctxt() => {
+        [.., prev, last] if prev.span.eq_ctxt(last.span) => {
             if let Ok(snippet) = sm.span_to_snippet(prev.span.between(last.span)) {
-                let comma =
-                    if matches!(last.body.kind, hir::ExprKind::Block(..)) { "" } else { "," };
+                let comma = if matches!(last.body.kind, hir::ExprKind::Block(..))
+                    && last.span.eq_ctxt(last.body.span)
+                {
+                    ""
+                } else {
+                    ","
+                };
                 suggestion = Some((
                     last.span.shrink_to_hi(),
                     format!(

compiler/rustc_mir_transform/src/coverage/mod.rs

@@ -121,7 +121,7 @@ impl<'a, 'tcx> Instrumentor<'a, 'tcx> {
 
         let source_file = source_map.lookup_source_file(body_span.lo());
         let fn_sig_span = match some_fn_sig.filter(|fn_sig| {
-            fn_sig.span.ctxt() == body_span.ctxt()
+            fn_sig.span.eq_ctxt(body_span)
                 && Lrc::ptr_eq(&source_file, &source_map.lookup_source_file(fn_sig.span.lo()))
         }) {
             Some(fn_sig) => fn_sig.span.with_hi(body_span.lo()),

compiler/rustc_mir_transform/src/coverage/spans.rs

@@ -195,7 +195,7 @@ impl CoverageSpan {
             .expn_span
             .parent_callsite()
             .unwrap_or_else(|| bug!("macro must have a parent"))
-            .ctxt() == body_span.ctxt()
+            .eq_ctxt(body_span)
         {
             return Some(current_macro);
         }

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -1894,7 +1894,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
         let names = rib
             .bindings
             .iter()
-            .filter(|(id, _)| id.span.ctxt() == label.span.ctxt())
+            .filter(|(id, _)| id.span.eq_ctxt(label.span))
             .map(|(id, _)| id.name)
             .collect::<Vec<Symbol>>();
 

compiler/rustc_span/src/lib.rs

@@ -537,6 +537,9 @@ impl Span {
     pub fn ctxt(self) -> SyntaxContext {
         self.data_untracked().ctxt
     }
+    pub fn eq_ctxt(self, other: Span) -> bool {
+        self.data_untracked().ctxt == other.data_untracked().ctxt
+    }
     #[inline]
     pub fn with_ctxt(self, ctxt: SyntaxContext) -> Span {
         self.data_untracked().with_ctxt(ctxt)

compiler/rustc_span/src/symbol.rs

@@ -1641,7 +1641,7 @@ impl Ident {
 
 impl PartialEq for Ident {
     fn eq(&self, rhs: &Self) -> bool {
-        self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
+        self.name == rhs.name && self.span.eq_ctxt(rhs.span)
     }
 }