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Mis-calculated spans #43796

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aidanhs opened this issue Aug 10, 2017 · 2 comments
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Mis-calculated spans #43796

aidanhs opened this issue Aug 10, 2017 · 2 comments
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A-save-analysis Area: saving results of analyses such as inference and borrowck results to a file. C-bug Category: This is a bug. T-dev-tools Relevant to the dev-tools subteam, which will review and decide on the PR/issue. T-infra Relevant to the infrastructure team, which will review and decide on the PR/issue.

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@aidanhs
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aidanhs commented Aug 10, 2017 

[00:33:43] ERROR:rustc_save_analysis::dump_visitor: Mis-calculated spans for path 'AsRef<U>::as_ref'. Found 1 spans, expected 2. Found spans:
[00:33:43] ERROR:rustc_save_analysis::dump_visitor:     'as_ref' in /checkout/src/libcore/convert.rs, line 355

This has been seen in a few different places, e.g.

I don't think it actually causes build failures, but it seems suspicious and something that should be fixed. I'll use logobble to dig up some more tomorrowish.
@Mark-Simulacrum Mark-Simulacrum added C-bug Category: This is a bug. T-dev-tools Relevant to the dev-tools subteam, which will review and decide on the PR/issue. T-infra Relevant to the infrastructure team, which will review and decide on the PR/issue. A-rls A-save-analysis Area: saving results of analyses such as inference and borrowck results to a file. and removed A-rls labels Aug 11, 2017
@Mark-Simulacrum
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cc @nrc -- any ideas on what could be causing this?

@kennytm kennytm mentioned this issue Aug 12, 2017
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@kennytm
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kennytm commented Aug 12, 2017

The problem is that SpanUtils::spans_with_brackets (called from spans_for_path_segments) does not handle UFCS path at all. It will ignore everything between angle brackets, so input like <T as AsRef<U>>::as_ref will only produce the span for as_ref (one segment).

However, the ast::Path of this will be AsRef<U>::as_ref (two segments), thus the mismatch error.

Thanks to #40369, each PathSegment already contain the span, so we shouldn't need to use spans_for_path_segments anymore.

@kennytm kennytm mentioned this issue Aug 12, 2017
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kennytm added a commit to kennytm/rust that referenced this issue Aug 14, 2017
@kennytm
save-analysis: Remove path span extraction methods from SpanUtils
60377e4 
Use the `span` field in PathSegment and TyParam instead.

Fix rust-lang#43796. Close rust-lang#41478.
@kennytm kennytm mentioned this issue Aug 14, 2017
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bors added a commit that referenced this issue Aug 14, 2017
@bors
Auto merge of #43826 - kennytm:fix-43796-mis-calculated-spans, r=petr…
df511d5 
…ochenkov

Fix "Mis-calculated spans" errors from `-Z save-analysis` + refactoring

Removed the path span extraction methods from `SpanUtils`:

* spans_with_brackets
* spans_for_path_segments
* spans_for_ty_params

Use the `span` fields in `PathSegment` and `TyParam` instead.

(Note that since it processes `ast::Path` not a qualified path (`hir::QPath` / `ast::QSelf`), UFCS path will be flattened: `<Foo as a::b::c::Trait>::D::E::F::g` will be seen as `a::b::c::Trait::D::E::F::g`.)

Fix #43796. Close #41478.

r? @nrc
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A-save-analysis Area: saving results of analyses such as inference and borrowck results to a file. C-bug Category: This is a bug. T-dev-tools Relevant to the dev-tools subteam, which will review and decide on the PR/issue. T-infra Relevant to the infrastructure team, which will review and decide on the PR/issue.
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