Avoid unnecessary rustc_span::DUMMY_SP usage.

In some cases `DUMMY_SP` is already imported. In other cases this commit
adds the necessary import, in files where `DUMMY_SP` is used more than
once.

Author: nnethercote

compiler/rustc_ast_pretty/src/pprust/tests.rs

@@ -3,6 +3,7 @@ use super::*;
 use rustc_ast as ast;
 use rustc_span::create_default_session_globals_then;
 use rustc_span::symbol::Ident;
+use rustc_span::DUMMY_SP;
 use thin_vec::ThinVec;
 
 fn fun_to_string(
@@ -28,10 +29,7 @@ fn test_fun_to_string() {
     create_default_session_globals_then(|| {
         let abba_ident = Ident::from_str("abba");
 
-        let decl = ast::FnDecl {
-            inputs: ThinVec::new(),
-            output: ast::FnRetTy::Default(rustc_span::DUMMY_SP),
-        };
+        let decl = ast::FnDecl { inputs: ThinVec::new(), output: ast::FnRetTy::Default(DUMMY_SP) };
         let generics = ast::Generics::default();
         assert_eq!(
             fun_to_string(&decl, ast::FnHeader::default(), abba_ident, &generics),
@@ -48,15 +46,15 @@ fn test_variant_to_string() {
         let var = ast::Variant {
             ident,
             vis: ast::Visibility {
-                span: rustc_span::DUMMY_SP,
+                span: DUMMY_SP,
                 kind: ast::VisibilityKind::Inherited,
                 tokens: None,
             },
             attrs: ast::AttrVec::new(),
             id: ast::DUMMY_NODE_ID,
             data: ast::VariantData::Unit(ast::DUMMY_NODE_ID),
             disr_expr: None,
-            span: rustc_span::DUMMY_SP,
+            span: DUMMY_SP,
             is_placeholder: false,
         };
 

compiler/rustc_builtin_macros/src/deriving/generic/ty.rs

@@ -8,8 +8,7 @@ use rustc_ast::{self as ast, Expr, GenericArg, GenericParamKind, Generics, SelfK
 use rustc_expand::base::ExtCtxt;
 use rustc_span::source_map::respan;
 use rustc_span::symbol::{kw, Ident, Symbol};
-use rustc_span::Span;
-use rustc_span::DUMMY_SP;
+use rustc_span::{Span, DUMMY_SP};
 use thin_vec::ThinVec;
 
 /// A path, e.g., `::std::option::Option::<i32>` (global). Has support

compiler/rustc_hir_analysis/src/collect/predicates_of.rs

@@ -37,7 +37,7 @@ pub(super) fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredic
         // from the trait itself that *shouldn't* be shown as the source of
         // an obligation and instead be skipped. Otherwise we'd use
         // `tcx.def_span(def_id);`
-        let span = rustc_span::DUMMY_SP;
+        let span = DUMMY_SP;
 
         result.predicates =
             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((

compiler/rustc_hir_typeck/src/coercion.rs

@@ -59,8 +59,7 @@ use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt};
 use rustc_session::parse::feature_err;
 use rustc_span::symbol::sym;
-use rustc_span::DesugaringKind;
-use rustc_span::{BytePos, Span};
+use rustc_span::{BytePos, DesugaringKind, Span, DUMMY_SP};
 use rustc_target::spec::abi::Abi;
 use rustc_trait_selection::infer::InferCtxtExt as _;
 use rustc_trait_selection::traits::error_reporting::suggestions::TypeErrCtxtExt;
@@ -1045,7 +1044,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let source = self.resolve_vars_with_obligations(expr_ty);
         debug!("coercion::can_with_predicates({:?} -> {:?})", source, target);
 
-        let cause = self.cause(rustc_span::DUMMY_SP, ObligationCauseCode::ExprAssignable);
+        let cause = self.cause(DUMMY_SP, ObligationCauseCode::ExprAssignable);
         // We don't ever need two-phase here since we throw out the result of the coercion
         let coerce = Coerce::new(self, cause, AllowTwoPhase::No);
         self.probe(|_| {
@@ -1062,11 +1061,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// how many dereference steps needed to achieve `expr_ty <: target`. If
     /// it's not possible, return `None`.
     pub fn deref_steps(&self, expr_ty: Ty<'tcx>, target: Ty<'tcx>) -> Option<usize> {
-        let cause = self.cause(rustc_span::DUMMY_SP, ObligationCauseCode::ExprAssignable);
+        let cause = self.cause(DUMMY_SP, ObligationCauseCode::ExprAssignable);
         // We don't ever need two-phase here since we throw out the result of the coercion
         let coerce = Coerce::new(self, cause, AllowTwoPhase::No);
         coerce
-            .autoderef(rustc_span::DUMMY_SP, expr_ty)
+            .autoderef(DUMMY_SP, expr_ty)
             .find_map(|(ty, steps)| self.probe(|_| coerce.unify(ty, target)).ok().map(|_| steps))
     }
 
@@ -1077,7 +1076,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// trait or region sub-obligations. (presumably we could, but it's not
     /// particularly important for diagnostics...)
     pub fn deref_once_mutably_for_diagnostic(&self, expr_ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
-        self.autoderef(rustc_span::DUMMY_SP, expr_ty).nth(1).and_then(|(deref_ty, _)| {
+        self.autoderef(DUMMY_SP, expr_ty).nth(1).and_then(|(deref_ty, _)| {
             self.infcx
                 .type_implements_trait(
                     self.tcx.lang_items().deref_mut_trait()?,

compiler/rustc_hir_typeck/src/fallback.rs

@@ -5,6 +5,7 @@ use rustc_data_structures::{
 };
 use rustc_infer::infer::{DefineOpaqueTypes, InferOk};
 use rustc_middle::ty::{self, Ty};
+use rustc_span::DUMMY_SP;
 
 #[derive(Copy, Clone)]
 pub enum DivergingFallbackBehavior {
@@ -102,7 +103,7 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
         // that field is only used for type fallback diagnostics.
         for effect in unsolved_effects {
             let expected = self.tcx.consts.true_;
-            let cause = self.misc(rustc_span::DUMMY_SP);
+            let cause = self.misc(DUMMY_SP);
             match self.at(&cause, self.param_env).eq(DefineOpaqueTypes::Yes, expected, effect) {
                 Ok(InferOk { obligations, value: () }) => {
                     self.register_predicates(obligations);
@@ -165,11 +166,7 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
         };
         debug!("fallback_if_possible(ty={:?}): defaulting to `{:?}`", ty, fallback);
 
-        let span = self
-            .infcx
-            .type_var_origin(ty)
-            .map(|origin| origin.span)
-            .unwrap_or(rustc_span::DUMMY_SP);
+        let span = self.infcx.type_var_origin(ty).map(|origin| origin.span).unwrap_or(DUMMY_SP);
         self.demand_eqtype(span, ty, fallback);
         self.fallback_has_occurred.set(true);
         true

compiler/rustc_hir_typeck/src/method/confirm.rs

@@ -173,7 +173,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         let Some((ty, n)) = autoderef.nth(pick.autoderefs) else {
             return Ty::new_error_with_message(
                 self.tcx,
-                rustc_span::DUMMY_SP,
+                DUMMY_SP,
                 format!("failed autoderef {}", pick.autoderefs),
             );
         };
@@ -608,7 +608,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
                     let span = predicates
                         .iter()
                         .find_map(|(p, span)| if p == pred { Some(span) } else { None })
-                        .unwrap_or(rustc_span::DUMMY_SP);
+                        .unwrap_or(DUMMY_SP);
                     Some((trait_pred, span))
                 }
                 _ => None,

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -1844,23 +1844,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         has_unsuggestable_args = true;
                         match arg.unpack() {
                             GenericArgKind::Lifetime(_) => self
-                                .next_region_var(RegionVariableOrigin::MiscVariable(
-                                    rustc_span::DUMMY_SP,
-                                ))
+                                .next_region_var(RegionVariableOrigin::MiscVariable(DUMMY_SP))
                                 .into(),
                             GenericArgKind::Type(_) => self
                                 .next_ty_var(TypeVariableOrigin {
-                                    span: rustc_span::DUMMY_SP,
+                                    span: DUMMY_SP,
                                     param_def_id: None,
                                 })
                                 .into(),
                             GenericArgKind::Const(arg) => self
                                 .next_const_var(
                                     arg.ty(),
-                                    ConstVariableOrigin {
-                                        span: rustc_span::DUMMY_SP,
-                                        param_def_id: None,
-                                    },
+                                    ConstVariableOrigin { span: DUMMY_SP, param_def_id: None },
                                 )
                                 .into(),
                         }
@@ -2758,7 +2753,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let SelfSource::QPath(ty) = self_source else {
             return;
         };
-        for (deref_ty, _) in self.autoderef(rustc_span::DUMMY_SP, rcvr_ty).skip(1) {
+        for (deref_ty, _) in self.autoderef(DUMMY_SP, rcvr_ty).skip(1) {
             if let Ok(pick) = self.probe_for_name(
                 Mode::Path,
                 item_name,

compiler/rustc_mir_transform/src/gvn.rs

@@ -1202,7 +1202,7 @@ impl<'tcx> VnState<'_, 'tcx> {
             // not give the same value as the former mention.
             && value.is_deterministic()
         {
-            return Some(ConstOperand { span: rustc_span::DUMMY_SP, user_ty: None, const_: value });
+            return Some(ConstOperand { span: DUMMY_SP, user_ty: None, const_: value });
         }
 
         let op = self.evaluated[index].as_ref()?;
@@ -1219,7 +1219,7 @@ impl<'tcx> VnState<'_, 'tcx> {
         assert!(!value.may_have_provenance(self.tcx, op.layout.size));
 
         let const_ = Const::Val(value, op.layout.ty);
-        Some(ConstOperand { span: rustc_span::DUMMY_SP, user_ty: None, const_ })
+        Some(ConstOperand { span: DUMMY_SP, user_ty: None, const_ })
     }
 
     /// If there is a local which is assigned `index`, and its assignment strictly dominates `loc`,

compiler/rustc_parse/src/parser/item.rs

@@ -1968,11 +1968,8 @@ impl<'a> Parser<'a> {
         } else if matches!(is_raw, IdentIsRaw::No) && ident.is_reserved() {
             let snapshot = self.create_snapshot_for_diagnostic();
             let err = if self.check_fn_front_matter(false, Case::Sensitive) {
-                let inherited_vis = Visibility {
-                    span: rustc_span::DUMMY_SP,
-                    kind: VisibilityKind::Inherited,
-                    tokens: None,
-                };
+                let inherited_vis =
+                    Visibility { span: DUMMY_SP, kind: VisibilityKind::Inherited, tokens: None };
                 // We use `parse_fn` to get a span for the function
                 let fn_parse_mode = FnParseMode { req_name: |_| true, req_body: true };
                 match self.parse_fn(

compiler/rustc_trait_selection/src/traits/const_evaluatable.rs

@@ -8,15 +8,14 @@
 //! In this case we try to build an abstract representation of this constant using
 //! `thir_abstract_const` which can then be checked for structural equality with other
 //! generic constants mentioned in the `caller_bounds` of the current environment.
+
 use rustc_hir::def::DefKind;
 use rustc_infer::infer::InferCtxt;
 use rustc_middle::mir::interpret::ErrorHandled;
-
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::abstract_const::NotConstEvaluatable;
 use rustc_middle::ty::{self, TyCtxt, TypeVisitable, TypeVisitableExt, TypeVisitor};
-
-use rustc_span::Span;
+use rustc_span::{Span, DUMMY_SP};
 
 use crate::traits::ObligationCtxt;
 
@@ -116,12 +115,12 @@ pub fn is_const_evaluatable<'tcx>(
                 tcx.dcx()
                     .struct_span_fatal(
                         // Slightly better span than just using `span` alone
-                        if span == rustc_span::DUMMY_SP { tcx.def_span(uv.def) } else { span },
+                        if span == DUMMY_SP { tcx.def_span(uv.def) } else { span },
                         "failed to evaluate generic const expression",
                     )
                     .with_note("the crate this constant originates from uses `#![feature(generic_const_exprs)]`")
                     .with_span_suggestion_verbose(
-                        rustc_span::DUMMY_SP,
+                        DUMMY_SP,
                         "consider enabling this feature",
                         "#![feature(generic_const_exprs)]\n",
                         rustc_errors::Applicability::MaybeIncorrect,