Rollup merge of rust-lang#83526 - klensy:lazy-too, r=petrochenkov

lazily calls some fns

Replaced some fn's with it's lazy variants.

compiler/rustc_errors/src/json.rs

@@ -493,7 +493,7 @@ impl DiagnosticSpanLine {
  h_end: usize,
  ) -> DiagnosticSpanLine {
  DiagnosticSpanLine {
- text: sf.get_line(index).map_or(String::new(), |l| l.into_owned()),
+ text: sf.get_line(index).map_or_else(String::new, |l| l.into_owned()),
  highlight_start: h_start,
  highlight_end: h_end,
  }

compiler/rustc_middle/src/ty/instance.rs

@@ -216,9 +216,10 @@ impl<'tcx> InstanceDef<'tcx> {
  // drops of `Option::None` before LTO. We also respect the intent of
  // `#[inline]` on `Drop::drop` implementations.
  return ty.ty_adt_def().map_or(true, |adt_def| {
- adt_def.destructor(tcx).map_or(adt_def.is_enum(), |dtor| {
- tcx.codegen_fn_attrs(dtor.did).requests_inline()
- })
+ adt_def.destructor(tcx).map_or_else(
+ || adt_def.is_enum(),
+ |dtor| tcx.codegen_fn_attrs(dtor.did).requests_inline(),
+ )
  });
  }
  tcx.codegen_fn_attrs(self.def_id()).requests_inline()

compiler/rustc_middle/src/ty/query/on_disk_cache.rs

@@ -525,7 +525,7 @@ impl<'sess> OnDiskCache<'sess> {
  ) {
  let mut current_diagnostics = self.current_diagnostics.borrow_mut();
 
- let x = current_diagnostics.entry(dep_node_index).or_insert(Vec::new());
+ let x = current_diagnostics.entry(dep_node_index).or_default();
 
  x.extend(Into::<Vec<_>>::into(diagnostics));
  }

compiler/rustc_mir/src/borrow_check/diagnostics/outlives_suggestion.rs

@@ -157,7 +157,7 @@ impl OutlivesSuggestionBuilder {
  debug!("Collected {:?}: {:?}", fr, outlived_fr);
 
  // Add to set of constraints for final help note.
- self.constraints_to_add.entry(fr).or_insert(Vec::new()).push(outlived_fr);
+ self.constraints_to_add.entry(fr).or_default().push(outlived_fr);
  }
 
  /// Emit an intermediate note on the given `Diagnostic` if the involved regions are

compiler/rustc_resolve/src/late.rs

@@ -2327,7 +2327,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
 
  ExprKind::Call(ref callee, ref arguments) => {
  self.resolve_expr(callee, Some(expr));
- let const_args = self.r.legacy_const_generic_args(callee).unwrap_or(Vec::new());
+ let const_args = self.r.legacy_const_generic_args(callee).unwrap_or_default();
  for (idx, argument) in arguments.iter().enumerate() {
  // Constant arguments need to be treated as AnonConst since
  // that is how they will be later lowered to HIR.

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -184,7 +184,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
  PathResult::Module(ModuleOrUniformRoot::Module(module)) => module.res(),
  _ => None,
  }
- .map_or(String::new(), |res| format!("{} ", res.descr()));
+ .map_or_else(String::new, |res| format!("{} ", res.descr()));
  (mod_prefix, format!("`{}`", Segment::names_to_string(mod_path)))
  };
  (
@@ -1042,10 +1042,10 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
  if let Some(span) = self.def_span(def_id) {
  err.span_label(span, &format!("`{}` defined here", path_str));
  }
- let fields =
- self.r.field_names.get(&def_id).map_or("/* fields */".to_string(), |fields| {
-  vec!["_"; fields.len()].join(", ")
-  });
+ let fields = self.r.field_names.get(&def_id).map_or_else(
+ || "/* fields */".to_string(),
+ |fields| vec!["_"; fields.len()].join(", "),
+ );
  err.span_suggestion(
  span,
  "use the tuple variant pattern syntax instead",

library/test/src/helpers/exit_code.rs

@@ -4,7 +4,7 @@ use std::process::ExitStatus;
 
 #[cfg(not(unix))]
 pub fn get_exit_code(status: ExitStatus) -> Result<i32, String> {
- status.code().ok_or("received no exit code from child process".into())
+ status.code().ok_or_else(|| "received no exit code from child process".into())
 }
 
 #[cfg(unix)]