Improve spans for indexing expressions

Indexing is similar to method calls in having an arbitrary
left-hand-side and then something on the right, which is the main part
of the expression. Method calls already have a span for that right part,
but indexing does not. This means that long method chains that use
indexing have really bad spans, especially when the indexing panics and
that span in coverted into a panic location.

This does the same thing as method calls for the AST and HIR, storing an
extra span which is then put into the `fn_span` field in THIR.

Author: Noratrieb

clippy_lints/src/dereference.rs

@@ -800,7 +800,7 @@ fn in_postfix_position<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'tcx>) -> boo
         && parent.span.ctxt() == e.span.ctxt()
     {
         match parent.kind {
-            ExprKind::Call(child, _) | ExprKind::MethodCall(_, child, _, _) | ExprKind::Index(child, _)
+            ExprKind::Call(child, _) | ExprKind::MethodCall(_, child, _, _) | ExprKind::Index(child, _, _)
                 if child.hir_id == e.hir_id => true,
             ExprKind::Field(_, _) | ExprKind::Match(_, _, MatchSource::TryDesugar | MatchSource::AwaitDesugar) => true,
             _ => false,

clippy_lints/src/functions/must_use.rs

@@ -221,7 +221,7 @@ fn is_mutated_static(e: &hir::Expr<'_>) -> bool {
     match e.kind {
         Path(QPath::Resolved(_, path)) => !matches!(path.res, Res::Local(_)),
         Path(_) => true,
-        Field(inner, _) | Index(inner, _) => is_mutated_static(inner),
+        Field(inner, _) | Index(inner, _, _) => is_mutated_static(inner),
         _ => false,
     }
 }

clippy_lints/src/index_refutable_slice.rs

@@ -254,7 +254,7 @@ impl<'a, 'tcx> Visitor<'tcx> for SliceIndexLintingVisitor<'a, 'tcx> {
                 // Checking for slice indexing
                 let parent_id = map.parent_id(expr.hir_id);
                 if let Some(hir::Node::Expr(parent_expr)) = map.find(parent_id);
-                if let hir::ExprKind::Index(_, index_expr) = parent_expr.kind;
+                if let hir::ExprKind::Index(_, index_expr, _) = parent_expr.kind;
                 if let Some(Constant::Int(index_value)) = constant(cx, cx.typeck_results(), index_expr);
                 if let Ok(index_value) = index_value.try_into();
                 if index_value < max_suggested_slice;

clippy_lints/src/indexing_slicing.rs

@@ -103,7 +103,7 @@ impl<'tcx> LateLintPass<'tcx> for IndexingSlicing {
             return;
         }
 
-        if let ExprKind::Index(array, index) = &expr.kind {
+        if let ExprKind::Index(array, index, _) = &expr.kind {
             let note = "the suggestion might not be applicable in constant blocks";
             let ty = cx.typeck_results().expr_ty(array).peel_refs();
             if let Some(range) = higher::Range::hir(index) {

clippy_lints/src/loops/manual_memcpy.rs

@@ -60,8 +60,8 @@ pub(super) fn check<'tcx>(
                     o.and_then(|(lhs, rhs)| {
                         let rhs = fetch_cloned_expr(rhs);
                         if_chain! {
-                            if let ExprKind::Index(base_left, idx_left) = lhs.kind;
-                            if let ExprKind::Index(base_right, idx_right) = rhs.kind;
+                            if let ExprKind::Index(base_left, idx_left, _) = lhs.kind;
+                            if let ExprKind::Index(base_right, idx_right, _) = rhs.kind;
                             if let Some(ty) = get_slice_like_element_ty(cx, cx.typeck_results().expr_ty(base_left));
                             if get_slice_like_element_ty(cx, cx.typeck_results().expr_ty(base_right)).is_some();
                             if let Some((start_left, offset_left)) = get_details_from_idx(cx, idx_left, &starts);

clippy_lints/src/loops/needless_range_loop.rs

@@ -319,7 +319,7 @@ impl<'a, 'tcx> Visitor<'tcx> for VarVisitor<'a, 'tcx> {
 
         if_chain! {
             // an index op
-            if let ExprKind::Index(seqexpr, idx) = expr.kind;
+            if let ExprKind::Index(seqexpr, idx, _) = expr.kind;
             if !self.check(idx, seqexpr, expr);
             then {
                 return;

clippy_lints/src/loops/never_loop.rs

@@ -162,7 +162,7 @@ fn never_loop_expr<'tcx>(
         ExprKind::Binary(_, e1, e2)
         | ExprKind::Assign(e1, e2, _)
         | ExprKind::AssignOp(_, e1, e2)
-        | ExprKind::Index(e1, e2) => never_loop_expr_all(cx, &mut [e1, e2].iter().copied(), ignore_ids, main_loop_id),
+        | ExprKind::Index(e1, e2, _) => never_loop_expr_all(cx, &mut [e1, e2].iter().copied(), ignore_ids, main_loop_id),
         ExprKind::Loop(b, _, _, _) => {
             // Break can come from the inner loop so remove them.
             absorb_break(never_loop_block(cx, b, ignore_ids, main_loop_id))

clippy_lints/src/loops/while_let_on_iterator.rs

@@ -113,7 +113,7 @@ fn try_parse_iter_expr(cx: &LateContext<'_>, mut e: &Expr<'_>) -> Option<IterExp
 
             // Shouldn't have side effects, but there's no way to trace which field is used. So forget which fields have
             // already been seen.
-            ExprKind::Index(base, idx) if !idx.can_have_side_effects() => {
+            ExprKind::Index(base, idx, _) if !idx.can_have_side_effects() => {
                 can_move = false;
                 fields.clear();
                 e = base;

clippy_lints/src/manual_strip.rs

@@ -204,7 +204,7 @@ fn find_stripping<'tcx>(
             if_chain! {
                 if is_ref_str(self.cx, ex);
                 let unref = peel_ref(ex);
-                if let ExprKind::Index(indexed, index) = &unref.kind;
+                if let ExprKind::Index(indexed, index, _) = &unref.kind;
                 if let Some(higher::Range { start, end, .. }) = higher::Range::hir(index);
                 if let ExprKind::Path(path) = &indexed.kind;
                 if self.cx.qpath_res(path, ex.hir_id) == self.target;

clippy_lints/src/matches/match_on_vec_items.rs

@@ -12,7 +12,7 @@ use super::MATCH_ON_VEC_ITEMS;
 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, scrutinee: &'tcx Expr<'_>) {
     if_chain! {
         if let Some(idx_expr) = is_vec_indexing(cx, scrutinee);
-        if let ExprKind::Index(vec, idx) = idx_expr.kind;
+        if let ExprKind::Index(vec, idx, _) = idx_expr.kind;
 
         then {
             // FIXME: could be improved to suggest surrounding every pattern with Some(_),
@@ -36,7 +36,7 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, scrutinee: &'tcx Expr<'_>) {
 
 fn is_vec_indexing<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> Option<&'tcx Expr<'tcx>> {
     if_chain! {
-        if let ExprKind::Index(array, index) = expr.kind;
+        if let ExprKind::Index(array, index, _) = expr.kind;
         if is_vector(cx, array);
         if !is_full_range(cx, index);