Auto merge of #71717 - Dylan-DPC:rollup-av5vjor, r=Dylan-DPC

Rollup of 5 pull requests

Successful merges:

 - #70950 (extend NLL checker to understand `'empty` combined with universes)
 - #71433 (Add help message for missing right operand in condition)
 - #71449 (Move `{Free,}RegionRelations` and `FreeRegionMap` to `rustc_infer`)
 - #71559 (Detect git version before attempting to use --progress)
 - #71597 (Rename Unique::empty() -> Unique::dangling())

Failed merges:

r? @ghost

Cargo.lock

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

src/bootstrap/bootstrap.py

@@ -2,6 +2,7 @@
 import argparse
 import contextlib
 import datetime
+import distutils.version
 import hashlib
 import os
 import re
@@ -331,6 +332,7 @@ def __init__(self):
         self.use_locked_deps = ''
         self.use_vendored_sources = ''
         self.verbose = False
+        self.git_version = None
 
     def download_stage0(self):
         """Fetch the build system for Rust, written in Rust
@@ -743,15 +745,13 @@ def update_submodule(self, module, checked_out, recorded_submodules):
 
         run(["git", "submodule", "-q", "sync", module],
             cwd=self.rust_root, verbose=self.verbose)
-        try:
-            run(["git", "submodule", "update",
-                 "--init", "--recursive", "--progress", module],
-                cwd=self.rust_root, verbose=self.verbose, exception=True)
-        except RuntimeError:
-            # Some versions of git don't support --progress.
-            run(["git", "submodule", "update",
-                 "--init", "--recursive", module],
-                cwd=self.rust_root, verbose=self.verbose)
+
+        update_args = ["git", "submodule", "update", "--init", "--recursive"]
+        if self.git_version >= distutils.version.LooseVersion("2.11.0"):
+            update_args.append("--progress")
+        update_args.append(module)
+        run(update_args, cwd=self.rust_root, verbose=self.verbose, exception=True)
+
         run(["git", "reset", "-q", "--hard"],
             cwd=module_path, verbose=self.verbose)
         run(["git", "clean", "-qdfx"],
@@ -763,9 +763,13 @@ def update_submodules(self):
                 self.get_toml('submodules') == "false":
             return
 
-        # check the existence of 'git' command
+        default_encoding = sys.getdefaultencoding()
+
+        # check the existence and version of 'git' command
         try:
-            subprocess.check_output(['git', '--version'])
+            git_version_output = subprocess.check_output(['git', '--version'])
+            git_version_str = git_version_output.strip().split()[2].decode(default_encoding)
+            self.git_version = distutils.version.LooseVersion(git_version_str)
         except (subprocess.CalledProcessError, OSError):
             print("error: `git` is not found, please make sure it's installed and in the path.")
             sys.exit(1)

src/liballoc/raw_vec.rs

@@ -25,9 +25,9 @@ mod tests;
 /// involved. This type is excellent for building your own data structures like Vec and VecDeque.
 /// In particular:
 ///
-/// * Produces `Unique::empty()` on zero-sized types.
-/// * Produces `Unique::empty()` on zero-length allocations.
-/// * Avoids freeing `Unique::empty()`.
+/// * Produces `Unique::dangling()` on zero-sized types.
+/// * Produces `Unique::dangling()` on zero-length allocations.
+/// * Avoids freeing `Unique::dangling()`.
 /// * Catches all overflows in capacity computations (promotes them to "capacity overflow" panics).
 /// * Guards against 32-bit systems allocating more than isize::MAX bytes.
 /// * Guards against overflowing your length.
@@ -125,7 +125,7 @@ impl<T, A: AllocRef> RawVec<T, A> {
     /// the returned `RawVec`.
     pub const fn new_in(alloc: A) -> Self {
         // `cap: 0` means "unallocated". zero-sized types are ignored.
-        Self { ptr: Unique::empty(), cap: 0, alloc }
+        Self { ptr: Unique::dangling(), cap: 0, alloc }
     }
 
     /// Like `with_capacity`, but parameterized over the choice of
@@ -172,7 +172,7 @@ impl<T, A: AllocRef> RawVec<T, A> {
     }
 
     /// Gets a raw pointer to the start of the allocation. Note that this is
-    /// `Unique::empty()` if `capacity == 0` or `T` is zero-sized. In the former case, you must
+    /// `Unique::dangling()` if `capacity == 0` or `T` is zero-sized. In the former case, you must
     /// be careful.
     pub fn ptr(&self) -> *mut T {
         self.ptr.as_ptr()

src/libcore/ptr/unique.rs

@@ -70,9 +70,8 @@ impl<T: Sized> Unique<T> {
     /// a `T`, which means this must not be used as a "not yet initialized"
     /// sentinel value. Types that lazily allocate must track initialization by
     /// some other means.
-    // FIXME: rename to dangling() to match NonNull?
     #[inline]
-    pub const fn empty() -> Self {
+    pub const fn dangling() -> Self {
         // SAFETY: mem::align_of() returns a valid, non-null pointer. The
         // conditions to call new_unchecked() are thus respected.
         unsafe { Unique::new_unchecked(mem::align_of::<T>() as *mut T) }

src/librustc_data_structures/graph/scc/mod.rs

@@ -47,6 +47,11 @@ impl<N: Idx, S: Idx> Sccs<N, S> {
     }
 
     /// Returns an iterator over the SCCs in the graph.
+    ///
+    /// The SCCs will be iterated in **dependency order** (or **post order**),
+    /// meaning that if `S1 -> S2`, we will visit `S2` first and `S1` after.
+    /// This is convenient when the edges represent dependencies: when you visit
+    /// `S1`, the value for `S2` will already have been computed.
     pub fn all_sccs(&self) -> impl Iterator<Item = S> {
         (0..self.scc_data.len()).map(S::new)
     }

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 → 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;
@@ -472,6 +473,9 @@ pub enum NLLRegionVariableOrigin {
     /// from a `for<'a> T` binder). Meant to represent "any region".
     Placeholder(ty::PlaceholderRegion),
 
+    /// The variable we create to represent `'empty(U0)`.
+    RootEmptyRegion,
+
     Existential {
         /// If this is true, then this variable was created to represent a lifetime
         /// bound in a `for` binder. For example, it might have been created to
@@ -493,6 +497,7 @@ impl NLLRegionVariableOrigin {
             NLLRegionVariableOrigin::FreeRegion => true,
             NLLRegionVariableOrigin::Placeholder(..) => true,
             NLLRegionVariableOrigin::Existential { .. } => false,
+            NLLRegionVariableOrigin::RootEmptyRegion => false,
         }
     }
 

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/mod.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/ty/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;