rustc_mir_transform/coverage/
hir_info.rs

1use rustc_hir as hir;
2use rustc_hir::intravisit::{Visitor, walk_expr};
3use rustc_middle::hir::nested_filter;
4use rustc_middle::ty::TyCtxt;
5use rustc_span::Span;
6use rustc_span::def_id::LocalDefId;
7
8/// Function information extracted from HIR by the coverage instrumentor.
9#[derive(Debug)]
10pub(crate) struct ExtractedHirInfo {
11    pub(crate) function_source_hash: u64,
12    pub(crate) is_async_fn: bool,
13    /// The span of the function's signature, if available.
14    /// Must have the same context and filename as the body span.
15    pub(crate) fn_sig_span: Option<Span>,
16    pub(crate) body_span: Span,
17    /// "Holes" are regions within the function body (or its expansions) that
18    /// should not be included in coverage spans for this function
19    /// (e.g. closures and nested items).
20    pub(crate) hole_spans: Vec<Span>,
21}
22
23pub(crate) fn extract_hir_info<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> ExtractedHirInfo {
24    // FIXME(#79625): Consider improving MIR to provide the information needed, to avoid going back
25    // to HIR for it.
26
27    // HACK: For synthetic MIR bodies (async closures), use the def id of the HIR body.
28    if tcx.is_synthetic_mir(def_id) {
29        return extract_hir_info(tcx, tcx.local_parent(def_id));
30    }
31
32    let hir_node = tcx.hir_node_by_def_id(def_id);
33    let fn_body_id = hir_node.body_id().expect("HIR node is a function with body");
34    let hir_body = tcx.hir_body(fn_body_id);
35
36    let maybe_fn_sig = hir_node.fn_sig();
37    let is_async_fn = maybe_fn_sig.is_some_and(|fn_sig| fn_sig.header.is_async());
38
39    let mut body_span = hir_body.value.span;
40
41    use hir::{Closure, Expr, ExprKind, Node};
42    // Unexpand a closure's body span back to the context of its declaration.
43    // This helps with closure bodies that consist of just a single bang-macro,
44    // and also with closure bodies produced by async desugaring.
45    if let Node::Expr(&Expr { kind: ExprKind::Closure(&Closure { fn_decl_span, .. }), .. }) =
46        hir_node
47    {
48        body_span = body_span.find_ancestor_in_same_ctxt(fn_decl_span).unwrap_or(body_span);
49    }
50
51    // The actual signature span is only used if it has the same context and
52    // filename as the body, and precedes the body.
53    let fn_sig_span = maybe_fn_sig.map(|fn_sig| fn_sig.span).filter(|&fn_sig_span| {
54        let source_map = tcx.sess.source_map();
55        let file_idx = |span: Span| source_map.lookup_source_file_idx(span.lo());
56
57        fn_sig_span.eq_ctxt(body_span)
58            && fn_sig_span.hi() <= body_span.lo()
59            && file_idx(fn_sig_span) == file_idx(body_span)
60    });
61
62    let function_source_hash = hash_mir_source(tcx, hir_body);
63
64    let hole_spans = extract_hole_spans_from_hir(tcx, hir_body);
65
66    ExtractedHirInfo { function_source_hash, is_async_fn, fn_sig_span, body_span, hole_spans }
67}
68
69fn hash_mir_source<'tcx>(tcx: TyCtxt<'tcx>, hir_body: &'tcx hir::Body<'tcx>) -> u64 {
70    let owner = hir_body.id().hir_id.owner;
71    tcx.hir_owner_nodes(owner)
72        .opt_hash_including_bodies
73        .expect("hash should be present when coverage instrumentation is enabled")
74        .to_smaller_hash()
75        .as_u64()
76}
77
78fn extract_hole_spans_from_hir<'tcx>(tcx: TyCtxt<'tcx>, hir_body: &hir::Body<'tcx>) -> Vec<Span> {
79    struct HolesVisitor<'tcx> {
80        tcx: TyCtxt<'tcx>,
81        hole_spans: Vec<Span>,
82    }
83
84    impl<'tcx> Visitor<'tcx> for HolesVisitor<'tcx> {
85        /// We have special handling for nested items, but we still want to
86        /// traverse into nested bodies of things that are not considered items,
87        /// such as "anon consts" (e.g. array lengths).
88        type NestedFilter = nested_filter::OnlyBodies;
89
90        fn maybe_tcx(&mut self) -> TyCtxt<'tcx> {
91            self.tcx
92        }
93
94        /// We override `visit_nested_item` instead of `visit_item` because we
95        /// only need the item's span, not the item itself.
96        fn visit_nested_item(&mut self, id: hir::ItemId) -> Self::Result {
97            let span = self.tcx.def_span(id.owner_id.def_id);
98            self.visit_hole_span(span);
99            // Having visited this item, we don't care about its children,
100            // so don't call `walk_item`.
101        }
102
103        // We override `visit_expr` instead of the more specific expression
104        // visitors, so that we have direct access to the expression span.
105        fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
106            match expr.kind {
107                hir::ExprKind::Closure(_) | hir::ExprKind::ConstBlock(_) => {
108                    self.visit_hole_span(expr.span);
109                    // Having visited this expression, we don't care about its
110                    // children, so don't call `walk_expr`.
111                }
112
113                // For other expressions, recursively visit as normal.
114                _ => walk_expr(self, expr),
115            }
116        }
117    }
118    impl HolesVisitor<'_> {
119        fn visit_hole_span(&mut self, hole_span: Span) {
120            self.hole_spans.push(hole_span);
121        }
122    }
123
124    let mut visitor = HolesVisitor { tcx, hole_spans: vec![] };
125
126    visitor.visit_body(hir_body);
127    visitor.hole_spans
128}
rustc_mir_transform/coverage/hir_info.rs

rustc_mir_transform/coverage/
hir_info.rs
