Auto merge of #65885 - Centril:rollup-y6b2qbf, r=Centril

Rollup of 6 pull requests

Successful merges:

 - #64747 (Stabilize `Option::flatten`)
 - #65664 (`std::panic::Location` is a lang_item, add `core::intrinsics::caller_location` (RFC 2091 3/N))
 - #65792 (rustc, rustc_passes: reduce deps on rustc_expand)
 - #65849 (librustc_lexer: Enhance documentation)
 - #65873 (doc: explain why it is unsafe to construct Vec<u8> from Vec<u16>)
 - #65880 (Gather together usefulness tests)

Failed merges:

r? @ghost

7 files changed, 14 insertions, 10 deletions

diff --git a/src/libsyntax_ext/deriving/clone.rs b/src/libsyntax_ext/deriving/clone.rs
index 67ef69babdc..061afa379c6 100644
--- a/src/libsyntax_ext/deriving/clone.rs
+++ b/src/libsyntax_ext/deriving/clone.rs
@@ -3,7 +3,8 @@ use crate::deriving::generic::*;
 use crate::deriving::generic::ty::*;
 
 use syntax::ast::{self, Expr, GenericArg, Generics, ItemKind, MetaItem, VariantData};
-use syntax_expand::base::{Annotatable, ExtCtxt, SpecialDerives};
+use syntax::expand::SpecialDerives;
+use syntax_expand::base::{Annotatable, ExtCtxt};
 use syntax::ptr::P;
 use syntax::symbol::{kw, sym, Symbol};
 use syntax_pos::Span;
diff --git a/src/libsyntax_ext/deriving/cmp/eq.rs b/src/libsyntax_ext/deriving/cmp/eq.rs
index 162aaedafea..eddf8eea1db 100644
--- a/src/libsyntax_ext/deriving/cmp/eq.rs
+++ b/src/libsyntax_ext/deriving/cmp/eq.rs
@@ -3,9 +3,10 @@ use crate::deriving::generic::*;
 use crate::deriving::generic::ty::*;
 
 use syntax::ast::{self, Ident, Expr, MetaItem, GenericArg};
-use syntax_expand::base::{Annotatable, ExtCtxt, SpecialDerives};
+use syntax::expand::SpecialDerives;
 use syntax::ptr::P;
 use syntax::symbol::{sym, Symbol};
+use syntax_expand::base::{Annotatable, ExtCtxt};
 use syntax_pos::Span;
 
 pub fn expand_deriving_eq(cx: &mut ExtCtxt<'_>,
diff --git a/src/libsyntax_ext/deriving/cmp/partial_eq.rs b/src/libsyntax_ext/deriving/cmp/partial_eq.rs
index c3e2b78bbe5..2e2be91de8a 100644
--- a/src/libsyntax_ext/deriving/cmp/partial_eq.rs
+++ b/src/libsyntax_ext/deriving/cmp/partial_eq.rs
@@ -3,10 +3,11 @@ use crate::deriving::generic::*;
 use crate::deriving::generic::ty::*;
 
 use syntax::ast::{BinOpKind, Expr, MetaItem};
-use syntax_expand::base::{Annotatable, ExtCtxt, SpecialDerives};
+use syntax::expand::SpecialDerives;
 use syntax::ptr::P;
 use syntax::symbol::sym;
-use syntax_pos::{self, Span};
+use syntax_expand::base::{Annotatable, ExtCtxt};
+use syntax_pos::Span;
 
 pub fn expand_deriving_partial_eq(cx: &mut ExtCtxt<'_>,
                                   span: Span,
diff --git a/src/libsyntax_ext/deriving/generic/mod.rs b/src/libsyntax_ext/deriving/generic/mod.rs
index 216338c1a88..c04b65245e1 100644
--- a/src/libsyntax_ext/deriving/generic/mod.rs
+++ b/src/libsyntax_ext/deriving/generic/mod.rs
@@ -186,13 +186,14 @@ use rustc_target::spec::abi::Abi;
 use syntax::ast::{self, BinOpKind, EnumDef, Expr, Generics, Ident, PatKind};
 use syntax::ast::{VariantData, GenericParamKind, GenericArg};
 use syntax::attr;
+use syntax::expand::SpecialDerives;
 use syntax::source_map::respan;
 use syntax::util::map_in_place::MapInPlace;
 use syntax::ptr::P;
 use syntax::sess::ParseSess;
 use syntax::symbol::{Symbol, kw, sym};
-use syntax_expand::base::{Annotatable, ExtCtxt, SpecialDerives};
-use syntax_pos::{Span};
+use syntax_expand::base::{Annotatable, ExtCtxt};
+use syntax_pos::Span;
 
 use ty::{LifetimeBounds, Path, Ptr, PtrTy, Self_, Ty};
 
diff --git a/src/libsyntax_ext/global_allocator.rs b/src/libsyntax_ext/global_allocator.rs
index 75dda9535b3..90d2ea38bc3 100644
--- a/src/libsyntax_ext/global_allocator.rs
+++ b/src/libsyntax_ext/global_allocator.rs
@@ -2,10 +2,10 @@ use crate::util::check_builtin_macro_attribute;
 
 use syntax::ast::{ItemKind, Mutability, Stmt, Ty, TyKind, Unsafety};
 use syntax::ast::{self, Param, Attribute, Expr, FnHeader, Generics, Ident};
-use syntax_expand::allocator::{AllocatorKind, AllocatorMethod, AllocatorTy, ALLOCATOR_METHODS};
-use syntax_expand::base::{Annotatable, ExtCtxt};
+use syntax::expand::allocator::{AllocatorKind, AllocatorMethod, AllocatorTy, ALLOCATOR_METHODS};
 use syntax::ptr::P;
 use syntax::symbol::{kw, sym, Symbol};
+use syntax_expand::base::{Annotatable, ExtCtxt};
 use syntax_pos::Span;
 
 pub fn expand(
diff --git a/src/libsyntax_ext/proc_macro_harness.rs b/src/libsyntax_ext/proc_macro_harness.rs
index c874f1ffb11..fc4a7a0a0fe 100644
--- a/src/libsyntax_ext/proc_macro_harness.rs
+++ b/src/libsyntax_ext/proc_macro_harness.rs
@@ -3,6 +3,7 @@ use std::mem;
 use smallvec::smallvec;
 use syntax::ast::{self, Ident};
 use syntax::attr;
+use syntax::expand::is_proc_macro_attr;
 use syntax::print::pprust;
 use syntax::ptr::P;
 use syntax::sess::ParseSess;
@@ -10,7 +11,6 @@ use syntax::symbol::{kw, sym};
 use syntax::visit::{self, Visitor};
 use syntax_expand::base::{ExtCtxt, Resolver};
 use syntax_expand::expand::{AstFragment, ExpansionConfig};
-use syntax_expand::proc_macro::is_proc_macro_attr;
 use syntax_pos::{Span, DUMMY_SP};
 use syntax_pos::hygiene::AstPass;
 
diff --git a/src/libsyntax_ext/standard_library_imports.rs b/src/libsyntax_ext/standard_library_imports.rs
index fd27a218906..6514ff5e252 100644
--- a/src/libsyntax_ext/standard_library_imports.rs
+++ b/src/libsyntax_ext/standard_library_imports.rs
@@ -4,9 +4,9 @@ use syntax::ptr::P;
 use syntax::sess::ParseSess;
 use syntax::symbol::{Ident, Symbol, kw, sym};
 use syntax_expand::expand::ExpansionConfig;
-use syntax_expand::hygiene::AstPass;
 use syntax_expand::base::{ExtCtxt, Resolver};
 use syntax_pos::DUMMY_SP;
+use syntax_pos::hygiene::AstPass;
 
 pub fn inject(
     mut krate: ast::Crate,