Rollup merge of rust-lang#99140 - TaKO8Ki:implement-is-accessible-span, r=fee1-dead

Implement `SourceMap::is_span_accessible`

This patch adds `SourceMap::is_span_accessible` and replaces `span_to_snippet(span).is_ok()` and `span_to_snippet(span).is_err()` with it. This removes a `&str` to `String` conversion.

Author: Dylan-DPC

Diff for: compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -309,7 +309,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 ));
 
                 // Check first whether the source is accessible (issue #87060)
-                if self.infcx.tcx.sess.source_map().span_to_snippet(deref_target).is_ok() {
+                if self.infcx.tcx.sess.source_map().is_span_accessible(deref_target) {
                     err.span_note(deref_target, "deref defined here");
                 }
             }

Diff for: compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -975,14 +975,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     if self.fn_self_span_reported.insert(fn_span) {
                         err.span_note(
                             // Check whether the source is accessible
-                            if self
-                                .infcx
-                                .tcx
-                                .sess
-                                .source_map()
-                                .span_to_snippet(self_arg.span)
-                                .is_ok()
-                            {
+                            if self.infcx.tcx.sess.source_map().is_span_accessible(self_arg.span) {
                                 self_arg.span
                             } else {
                                 fn_call_span

Diff for: compiler/rustc_const_eval/src/transform/check_consts/ops.rs

@@ -299,7 +299,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
                 err.note(&format!("attempting to deref into `{}`", deref_target_ty));
 
                 // Check first whether the source is accessible (issue #87060)
-                if tcx.sess.source_map().span_to_snippet(deref_target).is_ok() {
+                if tcx.sess.source_map().is_span_accessible(deref_target) {
                     err.span_note(deref_target, "deref defined here");
                 }
 

Diff for: compiler/rustc_errors/src/lib.rs

@@ -1558,7 +1558,7 @@ pub fn add_elided_lifetime_in_path_suggestion(
     insertion_span: Span,
 ) {
     diag.span_label(path_span, format!("expected lifetime parameter{}", pluralize!(n)));
-    if source_map.span_to_snippet(insertion_span).is_err() {
+    if !source_map.is_span_accessible(insertion_span) {
         // Do not try to suggest anything if generated by a proc-macro.
         return;
     }

Diff for: compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -432,7 +432,7 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
                 "`let` bindings require an \"irrefutable pattern\", like a `struct` or \
                  an `enum` with only one variant",
             );
-            if self.tcx.sess.source_map().span_to_snippet(span).is_ok() {
+            if self.tcx.sess.source_map().is_span_accessible(span) {
                 let semi_span = span.shrink_to_hi().with_lo(span.hi() - BytePos(1));
                 let start_span = span.shrink_to_lo();
                 let end_span = semi_span.shrink_to_lo();

Diff for: compiler/rustc_resolve/src/diagnostics.rs

@@ -1647,7 +1647,7 @@ impl<'a> Resolver<'a> {
 
     fn binding_description(&self, b: &NameBinding<'_>, ident: Ident, from_prelude: bool) -> String {
         let res = b.res();
-        if b.span.is_dummy() || self.session.source_map().span_to_snippet(b.span).is_err() {
+        if b.span.is_dummy() || !self.session.source_map().is_span_accessible(b.span) {
             // These already contain the "built-in" prefix or look bad with it.
             let add_built_in =
                 !matches!(b.res(), Res::NonMacroAttr(..) | Res::PrimTy(..) | Res::ToolMod);

Diff for: compiler/rustc_span/src/source_map.rs

@@ -597,6 +597,13 @@ impl SourceMap {
         local_begin.sf.src.is_some() && local_end.sf.src.is_some()
     }
 
+    pub fn is_span_accessible(&self, sp: Span) -> bool {
+        self.span_to_source(sp, |src, start_index, end_index| {
+            Ok(src.get(start_index..end_index).is_some())
+        })
+        .map_or(false, |is_accessible| is_accessible)
+    }
+
     /// Returns the source snippet as `String` corresponding to the given `Span`.
     pub fn span_to_snippet(&self, sp: Span) -> Result<String, SpanSnippetError> {
         self.span_to_source(sp, |src, start_index, end_index| {

Diff for: compiler/rustc_typeck/src/check/demand.rs

@@ -760,7 +760,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     if let Some(call_span) =
                         iter::successors(Some(expr.span), |s| s.parent_callsite())
                             .find(|&s| sp.contains(s))
-                        && sm.span_to_snippet(call_span).is_ok()
+                        && sm.is_span_accessible(call_span)
                     {
                         return Some((
                             sp.with_hi(call_span.lo()),
@@ -773,7 +773,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     return None;
                 }
                 if sp.contains(expr.span)
-                    && sm.span_to_snippet(expr.span).is_ok()
+                    && sm.is_span_accessible(expr.span)
                 {
                     return Some((
                         sp.with_hi(expr.span.lo()),

Diff for: compiler/rustc_typeck/src/structured_errors/wrong_number_of_generic_args.rs

@@ -812,7 +812,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
     /// Builds the `type defined here` message.
     fn show_definition(&self, err: &mut Diagnostic) {
         let mut spans: MultiSpan = if let Some(def_span) = self.tcx.def_ident_span(self.def_id) {
-            if self.tcx.sess.source_map().span_to_snippet(def_span).is_ok() {
+            if self.tcx.sess.source_map().is_span_accessible(def_span) {
                 def_span.into()
             } else {
                 return;