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Auto merge of #84373 - cjgillot:resolve-span, r=michaelwoerister,petrochenkov

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Encode spans relative to the enclosing item

The aim of this PR is to avoid recomputing queries when code is moved without modification.

MCP at https://github.com/rust-lang/compiler-team/issues/443

This is achieved by :
1. storing the HIR owner LocalDefId information inside the span;
2. encoding and decoding spans relative to the enclosing item in the incremental on-disk cache;
3. marking a dependency to the `source_span(LocalDefId)` query when we translate a span from the short (`Span`) representation to its explicit (`SpanData`) representation.

Since all client code uses `Span`, step 3 ensures that all manipulations
of span byte positions actually create the dependency edge between
the caller and the `source_span(LocalDefId)`.
This query return the actual absolute span of the parent item.
As a consequence, any source code motion that changes the absolute byte position of a node will either:
- modify the distance to the parent's beginning, so change the relative span's hash;
- dirty `source_span`, and trigger the incremental recomputation of all code that
  depends on the span's absolute byte position.

With this scheme, I believe the dependency tracking to be accurate.

For the moment, the spans are marked during lowering.
I'd rather do this during def-collection,
but the AST MutVisitor is not practical enough just yet.
The only difference is that we attach macro-expanded spans
to their expansion point instead of the macro itself.
This commit is contained in:
bors 2021-09-11 23:35:28 +00:00
commit 547d9374d2
68 changed files with 2800 additions and 1170 deletions
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3
compiler/rustc_expand/src/base.rs
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@ -15,7 +15,7 @@ use rustc_lint_defs::builtin::PROC_MACRO_BACK_COMPAT;
use rustc_lint_defs::BuiltinLintDiagnostics;
use rustc_parse::{self, nt_to_tokenstream, parser, MACRO_ARGUMENTS};
use rustc_session::{parse::ParseSess, Limit, Session};
use rustc_span::def_id::{CrateNum, DefId};
use rustc_span::def_id::{CrateNum, DefId, LocalDefId};
use rustc_span::edition::Edition;
use rustc_span::hygiene::{AstPass, ExpnData, ExpnKind, LocalExpnId};
use rustc_span::source_map::SourceMap;
@ -843,6 +843,7 @@ pub type DeriveResolutions = Vec<(ast::Path, Annotatable, Option<Lrc<SyntaxExten
pub trait ResolverExpand {
fn next_node_id(&mut self) -> NodeId;
fn invocation_parent(&self, id: LocalExpnId) -> LocalDefId;
fn resolve_dollar_crates(&mut self);
fn visit_ast_fragment_with_placeholders(