Auto merge of #23002 - pnkfelix:fsk-box-place-runway, r=nikomatsakis

Runway for RFC 809 (overloaded box/placement-in) by adding type annotations or explicit calls to `Box::new` where I found it necessary on PR #22086.

I have broken this up into more than one PR because the entire commit chain (see PR #22086) is long, widespread and unwieldy to rebase frequently.

To my knowledge this is not a breaking change.  Also, there is in principle nothing stopping someone from reverting some/all of these annotations, since without the rest of the commit chain in #22086, the associated code would continue to compile.

All I can do is ask: Try to discourage others from removing seemingly "unnecessary" uses of the `Box` type or the `Box::new()` function, until the rest of RFC 809 lands.

18 files changed, 51 insertions, 49 deletions

diff --git a/src/libsyntax/diagnostic.rs b/src/libsyntax/diagnostic.rs
index a6f4974502c..e094cbcac53 100644
--- a/src/libsyntax/diagnostic.rs
+++ b/src/libsyntax/diagnostic.rs
@@ -223,7 +223,7 @@ pub fn mk_span_handler(handler: Handler, cm: codemap::CodeMap) -> SpanHandler {
 pub fn default_handler(color_config: ColorConfig,
                        registry: Option<diagnostics::registry::Registry>,
                        can_emit_warnings: bool) -> Handler {
-    mk_handler(can_emit_warnings, box EmitterWriter::stderr(color_config, registry))
+    mk_handler(can_emit_warnings, Box::new(EmitterWriter::stderr(color_config, registry)))
 }
 
 pub fn mk_handler(can_emit_warnings: bool, e: Box<Emitter + Send>) -> Handler {
@@ -352,11 +352,11 @@ impl EmitterWriter {
         if use_color {
             let dst = match term::stderr() {
                 Some(t) => Terminal(t),
-                None    => Raw(box stderr),
+                None    => Raw(Box::new(stderr)),
             };
             EmitterWriter { dst: dst, registry: registry }
         } else {
-            EmitterWriter { dst: Raw(box stderr), registry: registry }
+            EmitterWriter { dst: Raw(Box::new(stderr)), registry: registry }
         }
     }
 
diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index e5d1fe2388c..ad5ca627a93 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -465,7 +465,7 @@ fn initial_syntax_expander_table<'feat>(ecfg: &expand::ExpansionConfig<'feat>)
                                         -> SyntaxEnv {
     // utility function to simplify creating NormalTT syntax extensions
     fn builtin_normal_expander(f: MacroExpanderFn) -> SyntaxExtension {
-        NormalTT(box f, None)
+        NormalTT(Box::new(f), None)
     }
 
     let mut syntax_expanders = SyntaxEnv::new();
@@ -489,9 +489,9 @@ fn initial_syntax_expander_table<'feat>(ecfg: &expand::ExpansionConfig<'feat>)
                             builtin_normal_expander(
                                     ext::log_syntax::expand_syntax_ext));
     syntax_expanders.insert(intern("derive"),
-                            Decorator(box ext::deriving::expand_meta_derive));
+                            Decorator(Box::new(ext::deriving::expand_meta_derive)));
     syntax_expanders.insert(intern("deriving"),
-                            Decorator(box ext::deriving::expand_deprecated_deriving));
+                            Decorator(Box::new(ext::deriving::expand_deprecated_deriving)));
 
     if ecfg.enable_quotes() {
         // Quasi-quoting expanders
diff --git a/src/libsyntax/ext/deriving/clone.rs b/src/libsyntax/ext/deriving/clone.rs
index 5f460264216..f89f3ab55f3 100644
--- a/src/libsyntax/ext/deriving/clone.rs
+++ b/src/libsyntax/ext/deriving/clone.rs
@@ -40,9 +40,9 @@ pub fn expand_deriving_clone<F>(cx: &mut ExtCtxt,
                 args: Vec::new(),
                 ret_ty: Self_,
                 attributes: attrs,
-                combine_substructure: combine_substructure(box |c, s, sub| {
+                combine_substructure: combine_substructure(Box::new(|c, s, sub| {
                     cs_clone("Clone", c, s, sub)
-                }),
+                })),
             }
         ),
         associated_types: Vec::new(),
diff --git a/src/libsyntax/ext/deriving/cmp/eq.rs b/src/libsyntax/ext/deriving/cmp/eq.rs
index 80ef882745f..c02af437b1c 100644
--- a/src/libsyntax/ext/deriving/cmp/eq.rs
+++ b/src/libsyntax/ext/deriving/cmp/eq.rs
@@ -40,7 +40,7 @@ pub fn expand_deriving_eq<F>(cx: &mut ExtCtxt,
                 cx.expr_binary(span, ast::BiAnd, subexpr, eq)
             },
             cx.expr_bool(span, true),
-            box |cx, span, _, _| cx.expr_bool(span, false),
+            Box::new(|cx, span, _, _| cx.expr_bool(span, false)),
             cx, span, substr)
     }
     fn cs_ne(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<Expr> {
@@ -57,7 +57,7 @@ pub fn expand_deriving_eq<F>(cx: &mut ExtCtxt,
                 cx.expr_binary(span, ast::BiOr, subexpr, eq)
             },
             cx.expr_bool(span, false),
-            box |cx, span, _, _| cx.expr_bool(span, true),
+            Box::new(|cx, span, _, _| cx.expr_bool(span, true)),
             cx, span, substr)
     }
 
@@ -72,9 +72,9 @@ pub fn expand_deriving_eq<F>(cx: &mut ExtCtxt,
                 args: vec!(borrowed_self()),
                 ret_ty: Literal(path_local!(bool)),
                 attributes: attrs,
-                combine_substructure: combine_substructure(box |a, b, c| {
+                combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     $f(a, b, c)
-                })
+                }))
             }
         } }
     }
diff --git a/src/libsyntax/ext/deriving/cmp/ord.rs b/src/libsyntax/ext/deriving/cmp/ord.rs
index be4a33002aa..b2b26548018 100644
--- a/src/libsyntax/ext/deriving/cmp/ord.rs
+++ b/src/libsyntax/ext/deriving/cmp/ord.rs
@@ -38,9 +38,9 @@ pub fn expand_deriving_ord<F>(cx: &mut ExtCtxt,
                 args: vec!(borrowed_self()),
                 ret_ty: Literal(path_local!(bool)),
                 attributes: attrs,
-                combine_substructure: combine_substructure(box |cx, span, substr| {
+                combine_substructure: combine_substructure(Box::new(|cx, span, substr| {
                     cs_op($op, $equal, cx, span, substr)
-                })
+                }))
             }
         } }
     }
@@ -61,9 +61,9 @@ pub fn expand_deriving_ord<F>(cx: &mut ExtCtxt,
         args: vec![borrowed_self()],
         ret_ty: ret_ty,
         attributes: attrs,
-        combine_substructure: combine_substructure(box |cx, span, substr| {
+        combine_substructure: combine_substructure(Box::new(|cx, span, substr| {
             cs_partial_cmp(cx, span, substr)
-        })
+        }))
     };
 
     let trait_def = TraitDef {
@@ -175,13 +175,13 @@ pub fn cs_partial_cmp(cx: &mut ExtCtxt, span: Span,
             cx.expr_block(cx.block(span, vec!(assign), Some(if_)))
         },
         equals_expr.clone(),
-        box |cx, span, (self_args, tag_tuple), _non_self_args| {
+        Box::new(|cx, span, (self_args, tag_tuple), _non_self_args| {
             if self_args.len() != 2 {
                 cx.span_bug(span, "not exactly 2 arguments in `derive(PartialOrd)`")
             } else {
                 some_ordering_collapsed(cx, span, PartialCmpOp, tag_tuple)
             }
-        },
+        }),
         cx, span, substr)
 }
 
@@ -223,7 +223,7 @@ fn cs_op(less: bool, equal: bool, cx: &mut ExtCtxt,
             cx.expr_binary(span, ast::BiOr, cmp, and)
         },
         cx.expr_bool(span, equal),
-        box |cx, span, (self_args, tag_tuple), _non_self_args| {
+        Box::new(|cx, span, (self_args, tag_tuple), _non_self_args| {
             if self_args.len() != 2 {
                 cx.span_bug(span, "not exactly 2 arguments in `derive(PartialOrd)`")
             } else {
@@ -233,6 +233,6 @@ fn cs_op(less: bool, equal: bool, cx: &mut ExtCtxt,
                 };
                 some_ordering_collapsed(cx, span, op, tag_tuple)
             }
-        },
+        }),
         cx, span, substr)
 }
diff --git a/src/libsyntax/ext/deriving/cmp/totaleq.rs b/src/libsyntax/ext/deriving/cmp/totaleq.rs
index 31a754a1254..83164d242e8 100644
--- a/src/libsyntax/ext/deriving/cmp/totaleq.rs
+++ b/src/libsyntax/ext/deriving/cmp/totaleq.rs
@@ -32,7 +32,8 @@ pub fn expand_deriving_totaleq<F>(cx: &mut ExtCtxt,
             let block = cx.block(span, stmts, None);
             cx.expr_block(block)
         },
-                       box |cx, sp, _, _| cx.span_bug(sp, "non matching enums in derive(Eq)?"),
+                       Box::new(|cx, sp, _, _| {
+                           cx.span_bug(sp, "non matching enums in derive(Eq)?") }),
                        cx,
                        span,
                        substr)
@@ -57,9 +58,9 @@ pub fn expand_deriving_totaleq<F>(cx: &mut ExtCtxt,
                 args: vec!(),
                 ret_ty: nil_ty(),
                 attributes: attrs,
-                combine_substructure: combine_substructure(box |a, b, c| {
+                combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     cs_total_eq_assert(a, b, c)
-                })
+                }))
             }
         ),
         associated_types: Vec::new(),
diff --git a/src/libsyntax/ext/deriving/cmp/totalord.rs b/src/libsyntax/ext/deriving/cmp/totalord.rs
index 2f6f99bc1ee..1de955856e7 100644
--- a/src/libsyntax/ext/deriving/cmp/totalord.rs
+++ b/src/libsyntax/ext/deriving/cmp/totalord.rs
@@ -41,9 +41,9 @@ pub fn expand_deriving_totalord<F>(cx: &mut ExtCtxt,
                 args: vec!(borrowed_self()),
                 ret_ty: Literal(path_std!(cx, core::cmp::Ordering)),
                 attributes: attrs,
-                combine_substructure: combine_substructure(box |a, b, c| {
+                combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     cs_cmp(a, b, c)
-                }),
+                })),
             }
         ),
         associated_types: Vec::new(),
@@ -131,12 +131,12 @@ pub fn cs_cmp(cx: &mut ExtCtxt, span: Span,
             cx.expr_block(cx.block(span, vec!(assign), Some(if_)))
         },
         cx.expr_path(equals_path.clone()),
-        box |cx, span, (self_args, tag_tuple), _non_self_args| {
+        Box::new(|cx, span, (self_args, tag_tuple), _non_self_args| {
             if self_args.len() != 2 {
                 cx.span_bug(span, "not exactly 2 arguments in `derives(Ord)`")
             } else {
                 ordering_collapsed(cx, span, tag_tuple)
             }
-        },
+        }),
         cx, span, substr)
 }
diff --git a/src/libsyntax/ext/deriving/decodable.rs b/src/libsyntax/ext/deriving/decodable.rs
index f27bbc338e5..6ce68948e4b 100644
--- a/src/libsyntax/ext/deriving/decodable.rs
+++ b/src/libsyntax/ext/deriving/decodable.rs
@@ -82,9 +82,9 @@ fn expand_deriving_decodable_imp<F>(cx: &mut ExtCtxt,
                     true
                 )),
                 attributes: Vec::new(),
-                combine_substructure: combine_substructure(box |a, b, c| {
+                combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     decodable_substructure(a, b, c, krate)
-                }),
+                })),
             }
         ),
         associated_types: Vec::new(),
diff --git a/src/libsyntax/ext/deriving/default.rs b/src/libsyntax/ext/deriving/default.rs
index c10975a2d32..f9991a23354 100644
--- a/src/libsyntax/ext/deriving/default.rs
+++ b/src/libsyntax/ext/deriving/default.rs
@@ -40,9 +40,9 @@ pub fn expand_deriving_default<F>(cx: &mut ExtCtxt,
                 args: Vec::new(),
                 ret_ty: Self_,
                 attributes: attrs,
-                combine_substructure: combine_substructure(box |a, b, c| {
+                combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     default_substructure(a, b, c)
-                })
+                }))
             }
         ),
         associated_types: Vec::new(),
diff --git a/src/libsyntax/ext/deriving/encodable.rs b/src/libsyntax/ext/deriving/encodable.rs
index 17687534d75..d7961d7da00 100644
--- a/src/libsyntax/ext/deriving/encodable.rs
+++ b/src/libsyntax/ext/deriving/encodable.rs
@@ -158,9 +158,9 @@ fn expand_deriving_encodable_imp<F>(cx: &mut ExtCtxt,
                     true
                 )),
                 attributes: Vec::new(),
-                combine_substructure: combine_substructure(box |a, b, c| {
+                combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     encodable_substructure(a, b, c)
-                }),
+                })),
             }
         ),
         associated_types: Vec::new(),
diff --git a/src/libsyntax/ext/deriving/hash.rs b/src/libsyntax/ext/deriving/hash.rs
index 2149c7a7f77..da80c7a0e6d 100644
--- a/src/libsyntax/ext/deriving/hash.rs
+++ b/src/libsyntax/ext/deriving/hash.rs
@@ -45,9 +45,9 @@ pub fn expand_deriving_hash<F>(cx: &mut ExtCtxt,
                 args: vec!(Ptr(box Literal(arg), Borrowed(None, MutMutable))),
                 ret_ty: nil_ty(),
                 attributes: vec![],
-                combine_substructure: combine_substructure(box |a, b, c| {
+                combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     hash_substructure(a, b, c)
-                })
+                }))
             }
         ),
         associated_types: Vec::new(),
diff --git a/src/libsyntax/ext/deriving/primitive.rs b/src/libsyntax/ext/deriving/primitive.rs
index 3b96292323a..b2d0a9f6b51 100644
--- a/src/libsyntax/ext/deriving/primitive.rs
+++ b/src/libsyntax/ext/deriving/primitive.rs
@@ -45,9 +45,9 @@ pub fn expand_deriving_from_primitive<F>(cx: &mut ExtCtxt,
                                            true)),
                 // #[inline] liable to cause code-bloat
                 attributes: attrs.clone(),
-                combine_substructure: combine_substructure(box |c, s, sub| {
+                combine_substructure: combine_substructure(Box::new(|c, s, sub| {
                     cs_from("i64", c, s, sub)
-                }),
+                })),
             },
             MethodDef {
                 name: "from_u64",
@@ -60,9 +60,9 @@ pub fn expand_deriving_from_primitive<F>(cx: &mut ExtCtxt,
                                            true)),
                 // #[inline] liable to cause code-bloat
                 attributes: attrs,
-                combine_substructure: combine_substructure(box |c, s, sub| {
+                combine_substructure: combine_substructure(Box::new(|c, s, sub| {
                     cs_from("u64", c, s, sub)
-                }),
+                })),
             }
         ),
         associated_types: Vec::new(),
diff --git a/src/libsyntax/ext/deriving/rand.rs b/src/libsyntax/ext/deriving/rand.rs
index 029b6535108..8a764fded6f 100644
--- a/src/libsyntax/ext/deriving/rand.rs
+++ b/src/libsyntax/ext/deriving/rand.rs
@@ -55,9 +55,9 @@ pub fn expand_deriving_rand<F>(cx: &mut ExtCtxt,
                 ),
                 ret_ty: Self_,
                 attributes: Vec::new(),
-                combine_substructure: combine_substructure(box |a, b, c| {
+                combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     rand_substructure(a, b, c)
-                })
+                }))
             }
         ),
         associated_types: Vec::new(),
diff --git a/src/libsyntax/ext/deriving/show.rs b/src/libsyntax/ext/deriving/show.rs
index 281f23f9e61..ce89c541fd4 100644
--- a/src/libsyntax/ext/deriving/show.rs
+++ b/src/libsyntax/ext/deriving/show.rs
@@ -46,9 +46,9 @@ pub fn expand_deriving_show<F>(cx: &mut ExtCtxt,
                 args: vec!(fmtr),
                 ret_ty: Literal(path_std!(cx, core::fmt::Result)),
                 attributes: Vec::new(),
-                combine_substructure: combine_substructure(box |a, b, c| {
+                combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     show_substructure(a, b, c)
-                })
+                }))
             }
         ],
         associated_types: Vec::new(),
diff --git a/src/libsyntax/ext/tt/macro_parser.rs b/src/libsyntax/ext/tt/macro_parser.rs
index ce513bc91f5..0ac78209b6f 100644
--- a/src/libsyntax/ext/tt/macro_parser.rs
+++ b/src/libsyntax/ext/tt/macro_parser.rs
@@ -479,7 +479,7 @@ pub fn parse(sess: &ParseSess,
                 }
                 rdr.next_token();
             } else /* bb_eis.len() == 1 */ {
-                let mut rust_parser = Parser::new(sess, cfg.clone(), box rdr.clone());
+                let mut rust_parser = Parser::new(sess, cfg.clone(), Box::new(rdr.clone()));
 
                 let mut ei = bb_eis.pop().unwrap();
                 match ei.top_elts.get_tt(ei.idx) {
diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index 67011ad21a6..db7db4b83ac 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -180,7 +180,7 @@ fn generic_extension<'cx>(cx: &'cx ExtCtxt,
                                            Some(named_matches),
                                            imported_from,
                                            rhs);
-                let mut p = Parser::new(cx.parse_sess(), cx.cfg(), box trncbr);
+                let mut p = Parser::new(cx.parse_sess(), cx.cfg(), Box::new(trncbr));
                 p.check_unknown_macro_variable();
                 // Let the context choose how to interpret the result.
                 // Weird, but useful for X-macros.
@@ -267,7 +267,7 @@ pub fn compile<'cx>(cx: &'cx mut ExtCtxt,
         _ => cx.span_bug(def.span, "wrong-structured rhs")
     };
 
-    let exp = box MacroRulesMacroExpander {
+    let exp: Box<_> = box MacroRulesMacroExpander {
         name: def.ident,
         imported_from: def.imported_from,
         lhses: lhses,
diff --git a/src/libsyntax/owned_slice.rs b/src/libsyntax/owned_slice.rs
index f5201d4a8bc..25f1f9b8480 100644
--- a/src/libsyntax/owned_slice.rs
+++ b/src/libsyntax/owned_slice.rs
@@ -30,7 +30,7 @@ impl<T:fmt::Debug> fmt::Debug for OwnedSlice<T> {
 
 impl<T> OwnedSlice<T> {
     pub fn empty() -> OwnedSlice<T> {
-        OwnedSlice  { data: box [] }
+        OwnedSlice  { data: Box::new([]) }
     }
 
     #[inline(never)]
diff --git a/src/libsyntax/parse/lexer/mod.rs b/src/libsyntax/parse/lexer/mod.rs
index 83d2bb0cc70..bbe1ddfd4cf 100644
--- a/src/libsyntax/parse/lexer/mod.rs
+++ b/src/libsyntax/parse/lexer/mod.rs
@@ -1484,8 +1484,9 @@ mod test {
     use std::old_io::util;
 
     fn mk_sh() -> diagnostic::SpanHandler {
-        let emitter = diagnostic::EmitterWriter::new(box util::NullWriter, None);
-        let handler = diagnostic::mk_handler(true, box emitter);
+        // FIXME (#22405): Replace `Box::new` with `box` here when/if possible.
+        let emitter = diagnostic::EmitterWriter::new(Box::new(util::NullWriter), None);
+        let handler = diagnostic::mk_handler(true, Box::new(emitter));
         diagnostic::mk_span_handler(handler, CodeMap::new())
     }