Change:
It'd be great with a minimal reproducible example, or your codebase if it's hard to minimize.
I don't have a repro and the code is not open source unfortunately.

Discussion:
return; } <ins> let (_, line_hi, col_hi) = match ctx.byte_pos_to_line_and_col(span.hi) { Some(pos) => pos, None => { Hash::hash(&TAG_INVALID_SPAN, hasher); span.ctxt.hash_stable(ctx, hasher); return; } }; </ins> Hash::hash(&TAG_VALID_SPAN, hasher); // We truncate the stable ID hash and line and column numbers. The chances // of causing a collision this way should be minimal. Hash::hash(&(file_lo.name_hash as u64), hasher); <del> let col = (col_lo.0 as u64) & 0xFF; let line = ((line_lo as u64) & 0xFF_FF_FF) << 8; let len = ((span.hi - span.lo).0 as u64) << 32; let line_col_len = col | line | len; Hash::hash(&line_col_len, hasher); </del> <ins> // Hash both the length and the end location (line/column) of a span. If we // hash only the length, for example, then two otherwise equal spans with // different end locations will have the same hash. This can cause a problem // during incremental compilation wherein a previous result for a query that // depends on the end location of a span will be incorrectly reused when the // end location of the span it depends on has changed (see issue #74890). A // similar analysis applies if some query depends specifically on the length // of the span, but we only hash the end location. So hash both. let col_lo_trunc = (col_lo.0 as u64) & 0xFF; let line_lo_trunc = ((line_lo as u64) & 0xFF_FF_FF) << 8; let col_hi_trunc = (col_hi.0 as u64) & 0xFF << 32; let line_hi_trunc = ((line_hi as u64) & 0xFF_FF_FF) << 40; let col_line = col_lo_trunc | line_lo_trunc | col_hi_trunc | line_hi_trunc; let len = (span.hi - span.lo).0; Hash::hash(&col_line, hasher); Hash::hash(&len, hasher); </ins> span.ctxt.hash_stable(ctx, hasher); } }

<ins> include ../../run-make-fulldeps/tools.mk # FIXME https://github.com/rust-lang/rust/issues/78911 # ignore-32bit wrong/no cross compiler and sometimes we pass wrong gcc args (-m64) # Tests that we don't ICE during incremental compilation after modifying a # function span such that its previous end line exceeds the number of lines # in the new file, but its start line/column and length remain the same. SRC=$(TMPDIR)/src INCR=$(TMPDIR)/incr all: mkdir $(SRC) mkdir $(INCR) cp a.rs $(SRC)/main.rs $(RUSTC) -C incremental=$(INCR) $(SRC)/main.rs cp b.rs $(SRC)/main.rs $(RUSTC) -C incremental=$(INCR) $(SRC)/main.rs </ins>

<ins> fn main() { // foo must be used. foo(); } // For this test to operate correctly, foo's body must start on exactly the same // line and column and have the exact same length in bytes in a.rs and b.rs. In // a.rs, the body must end on a line number which does not exist in b.rs. // Basically, avoid modifying this file, including adding or removing whitespace! fn foo() { assert_eq!(1, 1); } </ins>

<ins> fn main() { // foo must be used. foo(); } // For this test to operate correctly, foo's body must start on exactly the same // line and column and have the exact same length in bytes in a.rs and b.rs. In // a.rs, the body must end on a line number which does not exist in b.rs. // Basically, avoid modifying this file, including adding or removing whitespace! fn foo() { assert_eq!(1, 1);//// } </ins>

include ../../run-make-fulldeps/tools.mk <ins> # FIXME https://github.com/rust-lang/rust/issues/78911 </ins> # ignore-32bit wrong/no cross compiler and sometimes we pass wrong gcc args (-m64) all: foo