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Rollup merge of #116974 - Zalathar:signature-spans, r=oli-obk,cjgillot

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coverage: Fix inconsistent handling of function signature spans

While doing some more cleanup of `spans`, I noticed a strange inconsistency in how function signatures are handled. Normally the function signature span is treated as though it were executable as part of the start of the function, but in some cases the signature span disappears entirely from coverage, for no obvious reason.

This is caused by the fact that spans created by `CoverageSpan::for_fn_sig` don't add the span to their `merged_spans` field (unlike normal statement/terminator spans). In cases where the span-processing code looks at those merged spans, it thinks the signature span is no longer visible and deletes it.

Adding the signature span to `merged_spans` resolves the inconsistency.

(Prior to #116409 this wouldn't have been possible, because there was no case in the old `CoverageStatement` enum representing a signature. Now that `merged_spans` is just a list of spans, that's no longer an obstacle.)
This commit is contained in:
Matthias Krüger 2023-10-21 10:08:17 +02:00 • committed by GitHub
commit e9df0b6b40
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9 changed files with 233 additions and 67 deletions
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33
compiler/rustc_mir_transform/src/coverage/spans.rs
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@ -2,7 +2,7 @@ use std::cell::OnceCell;
use rustc_data_structures::graph::WithNumNodes;
use rustc_index::IndexVec;
use rustc_middle::mir::{self, AggregateKind, Rvalue, Statement, StatementKind};
use rustc_middle::mir;
use rustc_span::{BytePos, ExpnKind, MacroKind, Span, Symbol, DUMMY_SP};
use super::graph::{BasicCoverageBlock, CoverageGraph, START_BCB};
@ -70,29 +70,15 @@ struct CoverageSpan {
impl CoverageSpan {
pub fn for_fn_sig(fn_sig_span: Span) -> Self {
Self {
span: fn_sig_span,
expn_span: fn_sig_span,
current_macro_or_none: Default::default(),
bcb: START_BCB,
merged_spans: vec![],
is_closure: false,
}
Self::new(fn_sig_span, fn_sig_span, START_BCB, false)
}
pub fn for_statement(
statement: &Statement<'_>,
pub(super) fn new(
span: Span,
expn_span: Span,
bcb: BasicCoverageBlock,
is_closure: bool,
) -> Self {
let is_closure = match statement.kind {
StatementKind::Assign(box (_, Rvalue::Aggregate(box ref kind, _))) => {
matches!(kind, AggregateKind::Closure(_, _) | AggregateKind::Coroutine(_, _, _))
}
_ => false,
};
Self {
span,
expn_span,
@ -103,17 +89,6 @@ impl CoverageSpan {
}
}
pub fn for_terminator(span: Span, expn_span: Span, bcb: BasicCoverageBlock) -> Self {
Self {
span,
expn_span,
current_macro_or_none: Default::default(),
bcb,
merged_spans: vec![span],
is_closure: false,
}
}
pub fn merge_from(&mut self, mut other: CoverageSpan) {
debug_assert!(self.is_mergeable(&other));
self.span = self.span.to(other.span);