Mark range expr with desugaring

Author: camsteffen

compiler/rustc_ast_lowering/src/expr.rs

@@ -62,6 +62,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     pub(super) fn lower_expr_mut(&mut self, e: &Expr) -> hir::Expr<'hir> {
         ensure_sufficient_stack(|| {
+            let mut span = self.lower_span(e.span);
             match &e.kind {
                 // Parenthesis expression does not have a HirId and is handled specially.
                 ExprKind::Paren(ex) => {
@@ -287,7 +288,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     self.lower_span(*brackets_span),
                 ),
                 ExprKind::Range(e1, e2, lims) => {
-                    self.lower_expr_range(e.span, e1.as_deref(), e2.as_deref(), *lims)
+                    span = self.mark_span_with_reason(DesugaringKind::RangeExpr, span, None);
+                    self.lower_expr_range(span, e1.as_deref(), e2.as_deref(), *lims)
                 }
                 ExprKind::Underscore => {
                     let guar = self.dcx().emit_err(UnderscoreExprLhsAssign { span: e.span });
@@ -379,7 +381,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 ExprKind::MacCall(_) => panic!("{:?} shouldn't exist here", e.span),
             };
 
-            hir::Expr { hir_id: expr_hir_id, kind, span: self.lower_span(e.span) }
+            hir::Expr { hir_id: expr_hir_id, kind, span }
         })
     }
 
@@ -1505,7 +1507,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     fn lower_expr_range_closed(&mut self, span: Span, e1: &Expr, e2: &Expr) -> hir::ExprKind<'hir> {
         let e1 = self.lower_expr_mut(e1);
         let e2 = self.lower_expr_mut(e2);
-        let fn_path = hir::QPath::LangItem(hir::LangItem::RangeInclusiveNew, self.lower_span(span));
+        let fn_path = hir::QPath::LangItem(hir::LangItem::RangeInclusiveNew, span);
         let fn_expr = self.arena.alloc(self.expr(span, hir::ExprKind::Path(fn_path)));
         hir::ExprKind::Call(fn_expr, arena_vec![self; e1, e2])
     }
@@ -1562,15 +1564,17 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let fields = self.arena.alloc_from_iter(
             e1.iter().map(|e| (sym::start, e)).chain(e2.iter().map(|e| (sym::end, e))).map(
                 |(s, e)| {
+                    let span = self.lower_span(e.span);
+                    let span = self.mark_span_with_reason(DesugaringKind::RangeExpr, span, None);
                     let expr = self.lower_expr(e);
-                    let ident = Ident::new(s, self.lower_span(e.span));
-                    self.expr_field(ident, expr, e.span)
+                    let ident = Ident::new(s, span);
+                    self.expr_field(ident, expr, span)
                 },
             ),
         );
 
         hir::ExprKind::Struct(
-            self.arena.alloc(hir::QPath::LangItem(lang_item, self.lower_span(span))),
+            self.arena.alloc(hir::QPath::LangItem(lang_item, span)),
             fields,
             hir::StructTailExpr::None,
         )

compiler/rustc_hir/src/hir.rs

@@ -23,7 +23,9 @@ use rustc_index::IndexVec;
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::source_map::Spanned;
-use rustc_span::{BytePos, DUMMY_SP, ErrorGuaranteed, Ident, Span, Symbol, kw, sym};
+use rustc_span::{
+    BytePos, DUMMY_SP, DesugaringKind, ErrorGuaranteed, Ident, Span, Symbol, kw, sym,
+};
 use rustc_target::asm::InlineAsmRegOrRegClass;
 use smallvec::SmallVec;
 use thin_vec::ThinVec;
@@ -2459,6 +2461,12 @@ impl Expr<'_> {
         }
     }
 
+    /// If this is a desugared range expression,
+    /// returns the span of the range without desugaring context.
+    pub fn range_span(&self) -> Option<Span> {
+        is_range_literal(self).then(|| self.span.parent_callsite().unwrap())
+    }
+
     /// Check if expression is an integer literal that can be used
     /// where `usize` is expected.
     pub fn is_size_lit(&self) -> bool {
@@ -2694,30 +2702,8 @@ impl Expr<'_> {
 /// Checks if the specified expression is a built-in range literal.
 /// (See: `LoweringContext::lower_expr()`).
 pub fn is_range_literal(expr: &Expr<'_>) -> bool {
-    match expr.kind {
-        // All built-in range literals but `..=` and `..` desugar to `Struct`s.
-        ExprKind::Struct(ref qpath, _, _) => matches!(
-            **qpath,
-            QPath::LangItem(
-                LangItem::Range
-                    | LangItem::RangeTo
-                    | LangItem::RangeFrom
-                    | LangItem::RangeFull
-                    | LangItem::RangeToInclusive
-                    | LangItem::RangeCopy
-                    | LangItem::RangeFromCopy
-                    | LangItem::RangeInclusiveCopy,
-                ..
-            )
-        ),
-
-        // `..=` desugars into `::std::ops::RangeInclusive::new(...)`.
-        ExprKind::Call(ref func, _) => {
-            matches!(func.kind, ExprKind::Path(QPath::LangItem(LangItem::RangeInclusiveNew, ..)))
-        }
-
-        _ => false,
-    }
+    matches!(expr.kind, ExprKind::Call(..) | ExprKind::Struct(..))
+        && expr.span.desugaring_kind() == Some(DesugaringKind::RangeExpr)
 }
 
 /// Checks if the specified expression needs parentheses for prefix

compiler/rustc_hir_typeck/src/expr.rs

@@ -2500,11 +2500,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .tcx
                 .sess
                 .source_map()
-                .span_extend_while_whitespace(range_start.span)
+                .span_extend_while_whitespace(range_start.expr.span)
                 .shrink_to_hi()
-                .to(range_end.span);
+                .to(range_end.expr.span);
 
-            err.subdiagnostic(TypeMismatchFruTypo { expr_span: range_start.span, fru_span, expr });
+            err.subdiagnostic(TypeMismatchFruTypo {
+                expr_span: range_start.expr.span,
+                fru_span,
+                expr,
+            });
 
             // Suppress any range expr type mismatches
             self.dcx().try_steal_replace_and_emit_err(

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -1600,25 +1600,27 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         match expr.kind {
             ExprKind::Struct(QPath::LangItem(LangItem::Range, ..), [start, end], _) => {
                 err.span_suggestion_verbose(
-                    start.span.shrink_to_hi().with_hi(end.span.lo()),
+                    start.expr.span.shrink_to_hi().with_hi(end.expr.span.lo()),
                     "remove the unnecessary `.` operator for a floating point literal",
                     '.',
                     Applicability::MaybeIncorrect,
                 );
                 true
             }
             ExprKind::Struct(QPath::LangItem(LangItem::RangeFrom, ..), [start], _) => {
+                let range_span = expr.span.parent_callsite().unwrap();
                 err.span_suggestion_verbose(
-                    expr.span.with_lo(start.span.hi()),
+                    range_span.with_lo(start.expr.span.hi()),
                     "remove the unnecessary `.` operator for a floating point literal",
                     '.',
                     Applicability::MaybeIncorrect,
                 );
                 true
             }
             ExprKind::Struct(QPath::LangItem(LangItem::RangeTo, ..), [end], _) => {
+                let range_span = expr.span.parent_callsite().unwrap();
                 err.span_suggestion_verbose(
-                    expr.span.until(end.span),
+                    range_span.until(end.expr.span),
                     "remove the unnecessary `.` operator and add an integer part for a floating point literal",
                     "0.",
                     Applicability::MaybeIncorrect,
@@ -2627,7 +2629,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         bool, /* suggest `&` or `&mut` type annotation */
     )> {
         let sess = self.sess();
-        let sp = expr.span;
+        let sp = expr.range_span().unwrap_or(expr.span);
         let sm = sess.source_map();
 
         // If the span is from an external macro, there's no suggestion we can make.

compiler/rustc_lint/src/types/literal.rs

@@ -1,4 +1,4 @@
-use hir::{ExprKind, Node, is_range_literal};
+use hir::{ExprKind, Node};
 use rustc_abi::{Integer, Size};
 use rustc_hir::{HirId, attrs};
 use rustc_middle::ty::Ty;
@@ -44,7 +44,7 @@ fn lint_overflowing_range_endpoint<'tcx>(
     let Node::Expr(struct_expr) = cx.tcx.parent_hir_node(field.hir_id) else {
         return false;
     };
-    if !is_range_literal(struct_expr) {
+    let Some(range_span) = struct_expr.range_span() else {
         return false;
     };
     let ExprKind::Struct(_, [start, end], _) = &struct_expr.kind else {
@@ -71,7 +71,7 @@ fn lint_overflowing_range_endpoint<'tcx>(
             return false;
         };
         UseInclusiveRange::WithoutParen {
-            sugg: struct_expr.span.shrink_to_lo().to(lit_span.shrink_to_hi()),
+            sugg: range_span.shrink_to_lo().to(lit_span.shrink_to_hi()),
             start,
             literal: lit_val - 1,
             suffix,
@@ -87,7 +87,7 @@ fn lint_overflowing_range_endpoint<'tcx>(
 
     cx.emit_span_lint(
         OVERFLOWING_LITERALS,
-        struct_expr.span,
+        range_span,
         RangeEndpointOutOfRange { ty, sub: sub_sugg },
     );
 

compiler/rustc_span/src/hygiene.rs

@@ -1237,6 +1237,7 @@ pub enum DesugaringKind {
         /// rewriting it.
         source: bool,
     },
+    RangeExpr,
 }
 
 impl DesugaringKind {
@@ -1258,6 +1259,7 @@ impl DesugaringKind {
             DesugaringKind::FormatLiteral { source: false } => {
                 "expression that expanded into a format string literal"
             }
+            DesugaringKind::RangeExpr => "range expression",
         }
     }
 
@@ -1277,6 +1279,7 @@ impl DesugaringKind {
             DesugaringKind::Contract => value == "Contract",
             DesugaringKind::PatTyRange => value == "PatTyRange",
             DesugaringKind::FormatLiteral { .. } => value == "FormatLiteral",
+            DesugaringKind::RangeExpr => value == "RangeExpr",
         }
     }
 }

src/tools/clippy/clippy_lints/src/loops/manual_memcpy.rs

@@ -27,6 +27,7 @@ pub(super) fn check<'tcx>(
         start: Some(start),
         end: Some(end),
         limits,
+        span: _,
     }) = higher::Range::hir(arg)
         // the var must be a single name
         && let PatKind::Binding(_, canonical_id, _, _) = pat.kind

src/tools/clippy/clippy_lints/src/loops/manual_slice_fill.rs

@@ -31,6 +31,7 @@ pub(super) fn check<'tcx>(
         start: Some(start),
         end: Some(end),
         limits: RangeLimits::HalfOpen,
+        span: _,
     }) = higher::Range::hir(arg)
         && let ExprKind::Lit(Spanned {
             node: LitKind::Int(Pu128(0), _),

src/tools/clippy/clippy_lints/src/loops/needless_range_loop.rs

@@ -30,6 +30,7 @@ pub(super) fn check<'tcx>(
         start: Some(start),
         ref end,
         limits,
+        span,
     }) = higher::Range::hir(arg)
         // the var must be a single name
         && let PatKind::Binding(_, canonical_id, ident, _) = pat.kind
@@ -149,15 +150,15 @@ pub(super) fn check<'tcx>(
                 span_lint_and_then(
                     cx,
                     NEEDLESS_RANGE_LOOP,
-                    arg.span,
+                    span,
                     format!("the loop variable `{}` is used to index `{indexed}`", ident.name),
                     |diag| {
                         diag.multipart_suggestion(
                             "consider using an iterator and enumerate()",
                             vec![
                                 (pat.span, format!("({}, <item>)", ident.name)),
                                 (
-                                    arg.span,
+                                    span,
                                     format!("{indexed}.{method}().enumerate(){method_1}{method_2}"),
                                 ),
                             ],
@@ -175,12 +176,12 @@ pub(super) fn check<'tcx>(
                 span_lint_and_then(
                     cx,
                     NEEDLESS_RANGE_LOOP,
-                    arg.span,
+                    span,
                     format!("the loop variable `{}` is only used to index `{indexed}`", ident.name),
                     |diag| {
                         diag.multipart_suggestion(
                             "consider using an iterator",
-                            vec![(pat.span, "<item>".to_string()), (arg.span, repl)],
+                            vec![(pat.span, "<item>".to_string()), (span, repl)],
                             Applicability::HasPlaceholders,
                         );
                     },

src/tools/clippy/clippy_lints/src/manual_is_ascii_check.rs

@@ -108,6 +108,7 @@ impl<'tcx> LateLintPass<'tcx> for ManualIsAsciiCheck {
                 start: Some(start),
                 end: Some(end),
                 limits: RangeLimits::Closed,
+                span: _,
             }) = higher::Range::hir(receiver)
             && !matches!(cx.typeck_results().expr_ty(arg).peel_refs().kind(), ty::Param(_))
         {