Rollup merge of #71449 - ecstatic-morse:free-region-cleanup, r=Mark-Simulacrum

Move `{Free,}RegionRelations` and `FreeRegionMap` to `rustc_infer`

...and out of `rustc_middle`. This is to further #65031, albeit in a very minor way

r? @Mark-Simulacrum

Author: Dylan-DPC

Cargo.lock

@@ -3852,6 +3852,7 @@ dependencies = [
  "rustc_session",
  "rustc_span",
  "rustc_target",
+ "serialize",
  "smallvec 1.0.0",
 ]
 

src/librustc_infer/Cargo.toml

@@ -19,6 +19,7 @@ rustc_hir = { path = "../librustc_hir" }
 rustc_index = { path = "../librustc_index" }
 rustc_macros = { path = "../librustc_macros" }
 rustc_session = { path = "../librustc_session" }
+rustc_serialize = { path = "../libserialize", package = "serialize" }
 rustc_span = { path = "../librustc_span" }
 rustc_target = { path = "../librustc_target" }
 smallvec = { version = "1.0", features = ["union", "may_dangle"] }

src/librustc_middle/ty/free_region_map.rs renamed to src/librustc_infer/infer/free_regions.rs

@@ -1,5 +1,47 @@
-use crate::ty::{self, Lift, Region, TyCtxt};
+//! This module handles the relationships between "free regions", i.e., lifetime parameters.
+//! Ordinarily, free regions are unrelated to one another, but they can be related via implied
+//! or explicit bounds. In that case, we track the bounds using the `TransitiveRelation` type,
+//! and use that to decide when one free region outlives another, and so forth.
+
 use rustc_data_structures::transitive_relation::TransitiveRelation;
+use rustc_hir::def_id::DefId;
+use rustc_middle::middle::region;
+use rustc_middle::ty::{self, Lift, Region, TyCtxt};
+
+/// Combines a `region::ScopeTree` (which governs relationships between
+/// scopes) and a `FreeRegionMap` (which governs relationships between
+/// free regions) to yield a complete relation between concrete
+/// regions.
+///
+/// This stuff is a bit convoluted and should be refactored, but as we
+/// transition to NLL, it'll all go away anyhow.
+pub struct RegionRelations<'a, 'tcx> {
+    pub tcx: TyCtxt<'tcx>,
+
+    /// The context used to fetch the region maps.
+    pub context: DefId,
+
+    /// The region maps for the given context.
+    pub region_scope_tree: &'a region::ScopeTree,
+
+    /// Free-region relationships.
+    pub free_regions: &'a FreeRegionMap<'tcx>,
+}
+
+impl<'a, 'tcx> RegionRelations<'a, 'tcx> {
+    pub fn new(
+        tcx: TyCtxt<'tcx>,
+        context: DefId,
+        region_scope_tree: &'a region::ScopeTree,
+        free_regions: &'a FreeRegionMap<'tcx>,
+    ) -> Self {
+        Self { tcx, context, region_scope_tree, free_regions }
+    }
+
+    pub fn lub_free_regions(&self, r_a: Region<'tcx>, r_b: Region<'tcx>) -> Region<'tcx> {
+        self.free_regions.lub_free_regions(self.tcx, r_a, r_b)
+    }
+}
 
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug, Default, HashStable)]
 pub struct FreeRegionMap<'tcx> {

src/librustc_infer/infer/lexical_region_resolve/graphviz.rs

@@ -10,10 +10,10 @@ use graphviz as dot;
 
 use super::Constraint;
 use crate::infer::region_constraints::RegionConstraintData;
+use crate::infer::RegionRelations;
 use crate::infer::SubregionOrigin;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir::def_id::DefIndex;
-use rustc_middle::middle::free_region::RegionRelations;
 use rustc_middle::middle::region;
 use rustc_middle::ty;
 

src/librustc_infer/infer/lexical_region_resolve/mod.rs

@@ -6,6 +6,7 @@ use crate::infer::region_constraints::MemberConstraint;
 use crate::infer::region_constraints::RegionConstraintData;
 use crate::infer::region_constraints::VarInfos;
 use crate::infer::region_constraints::VerifyBound;
+use crate::infer::RegionRelations;
 use crate::infer::RegionVariableOrigin;
 use crate::infer::RegionckMode;
 use crate::infer::SubregionOrigin;
@@ -14,7 +15,6 @@ use rustc_data_structures::graph::implementation::{
     Direction, Graph, NodeIndex, INCOMING, OUTGOING,
 };
 use rustc_index::vec::{Idx, IndexVec};
-use rustc_middle::middle::free_region::RegionRelations;
 use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_middle::ty::{ReEarlyBound, ReEmpty, ReErased, ReFree, ReStatic};

src/librustc_infer/infer/mod.rs

@@ -18,7 +18,6 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::infer::canonical::{Canonical, CanonicalVarValues};
 use rustc_middle::infer::unify_key::{ConstVarValue, ConstVariableValue};
 use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind, ToType};
-use rustc_middle::middle::free_region::RegionRelations;
 use rustc_middle::middle::region;
 use rustc_middle::mir;
 use rustc_middle::mir::interpret::ConstEvalResult;
@@ -39,6 +38,7 @@ use std::collections::BTreeMap;
 use std::fmt;
 
 use self::combine::CombineFields;
+use self::free_regions::RegionRelations;
 use self::lexical_region_resolve::LexicalRegionResolutions;
 use self::outlives::env::OutlivesEnvironment;
 use self::region_constraints::{GenericKind, RegionConstraintData, VarInfos, VerifyBound};
@@ -50,6 +50,7 @@ pub mod canonical;
 mod combine;
 mod equate;
 pub mod error_reporting;
+pub mod free_regions;
 mod freshen;
 mod fudge;
 mod glb;

src/librustc_infer/infer/outlives/env.rs

@@ -1,9 +1,9 @@
+use crate::infer::free_regions::FreeRegionMap;
 use crate::infer::{GenericKind, InferCtxt};
 use crate::traits::query::OutlivesBound;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir as hir;
 use rustc_middle::ty;
-use rustc_middle::ty::free_region_map::FreeRegionMap;
 
 use super::explicit_outlives_bounds;
 

src/librustc_middle/middle/free_region.rs

@@ -2,7 +2,6 @@ pub mod codegen_fn_attrs;
 pub mod cstore;
 pub mod dependency_format;
 pub mod exported_symbols;
-pub mod free_region;
 pub mod lang_items;
 pub mod lib_features {
     use rustc_data_structures::fx::{FxHashMap, FxHashSet};

src/librustc_middle/middle/mod.rs

@@ -96,7 +96,6 @@ pub mod error;
 pub mod fast_reject;
 pub mod flags;
 pub mod fold;
-pub mod free_region_map;
 pub mod inhabitedness;
 pub mod layout;
 pub mod normalize_erasing_regions;

src/librustc_middle/ty/mod.rs

@@ -1,12 +1,12 @@
 use rustc_data_structures::frozen::Frozen;
 use rustc_data_structures::transitive_relation::TransitiveRelation;
 use rustc_infer::infer::canonical::QueryRegionConstraints;
+use rustc_infer::infer::free_regions::FreeRegionRelations;
 use rustc_infer::infer::outlives;
 use rustc_infer::infer::region_constraints::GenericKind;
 use rustc_infer::infer::InferCtxt;
 use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::traits::query::OutlivesBound;
-use rustc_middle::ty::free_region_map::FreeRegionRelations;
 use rustc_middle::ty::{self, RegionVid, Ty, TyCtxt};
 use rustc_span::DUMMY_SP;
 use rustc_trait_selection::traits::query::type_op::{self, TypeOp};

src/librustc_mir/borrow_check/type_check/free_region_relations.rs

@@ -6,10 +6,10 @@ use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, DefIdMap, LocalDefId};
 use rustc_hir::Node;
 use rustc_infer::infer::error_reporting::unexpected_hidden_region_diagnostic;
+use rustc_infer::infer::free_regions::FreeRegionRelations;
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc_infer::infer::{self, InferCtxt, InferOk};
 use rustc_middle::ty::fold::{BottomUpFolder, TypeFoldable, TypeFolder, TypeVisitor};
-use rustc_middle::ty::free_region_map::FreeRegionRelations;
 use rustc_middle::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, SubstsRef};
 use rustc_middle::ty::{self, GenericParamDefKind, Ty, TyCtxt};
 use rustc_session::config::nightly_options;