rename elided_lifetimes_in_paths lint to hidden_lifetimes_in_types

It's only with reluctance and sadness that we rename a lint that has
already been renamed once (rust-lang#50879), but it seems worth it to pick the
best name now because since the lint is relatively new and has
heretofore been allow-by-default, the ecosystem breakage should be
minimal. (And—also sadly—the fact that the original implementation was
so buggy for so long testifies that not very many people are tuning up
the allow-by-default lints. Also, as always, lint capping prevents
lint changes from spreading contagiously to dependencies.)

The rationales here are that—

 • "hidden" is less potentially ambiguous than "elided", because this
   lint is specifically about angle-bracketed lifetime parameters,
   whereas the term "elided" has a strong precedent for also
   encompassing omitted lifetime names in reference ('&') types, which
   is not the concern of this lint, and

 • "types" is a more specific description of where the lint fires than
   "paths" (indeed, previous implementations of the lint used to fire
   on non-type paths in ways that proved to be erroneous
   false-positives, as evidenced by applications of the suggestion to
   use an anonymous lifetime (`'_`) resulting in code that didn't even
   parse)

This comes from discussion on rust-lang#52069.

Author: zackmdavis

src/librustc/lint/builtin.rs

@@ -250,9 +250,9 @@ declare_lint! {
 }
 
 declare_lint! {
-    pub ELIDED_LIFETIMES_IN_PATHS,
+    pub HIDDEN_LIFETIMES_IN_TYPES,
     Allow,
-    "implicit lifetime parameters are deprecated"
+    "hidden lifetime parameters in types are deprecated"
 }
 
 declare_lint! {
@@ -376,7 +376,7 @@ impl LintPass for HardwiredLints {
             UNUSED_LIFETIMES,
             UNUSED_LABELS,
             TYVAR_BEHIND_RAW_POINTER,
-            ELIDED_LIFETIMES_IN_PATHS,
+            HIDDEN_LIFETIMES_IN_TYPES,
             BARE_TRAIT_OBJECTS,
             ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE,
             UNSTABLE_NAME_COLLISIONS,

src/librustc/middle/resolve_lifetime.rs

@@ -2102,10 +2102,10 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
         }
 
         let mut err = self.tcx.struct_span_lint_node(
-            lint::builtin::ELIDED_LIFETIMES_IN_PATHS,
+            lint::builtin::HIDDEN_LIFETIMES_IN_TYPES,
             implicit_lifetimes[0].id, // FIXME: HirIdify #50928
             path.span,
-            &format!("implicit lifetime parameters in types are deprecated"),
+            &format!("hidden lifetime parameters in types are deprecated"),
         );
 
         if implicit_lifetimes.len() == 1 {

src/librustc_lint/lib.rs

@@ -45,7 +45,7 @@ extern crate syntax_pos;
 use rustc::lint;
 use rustc::lint::{LateContext, LateLintPass, LintPass, LintArray};
 use rustc::lint::builtin::{BARE_TRAIT_OBJECTS, ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE,
-                           ELIDED_LIFETIMES_IN_PATHS, MACRO_USE_EXTERN_CRATE};
+                           HIDDEN_LIFETIMES_IN_TYPES, MACRO_USE_EXTERN_CRATE};
 
 use rustc::session;
 use rustc::util;
@@ -184,7 +184,7 @@ pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
                     UNREACHABLE_PUB,
                     UNUSED_EXTERN_CRATES,
                     MACRO_USE_EXTERN_CRATE,
-                    ELIDED_LIFETIMES_IN_PATHS,
+                    HIDDEN_LIFETIMES_IN_TYPES,
                     ELLIPSIS_INCLUSIVE_RANGE_PATTERNS);
 
     // Guidelines for creating a future incompatibility lint:
@@ -308,11 +308,14 @@ pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
 
     // Register renamed and removed lints
     store.register_renamed("single_use_lifetime", "single_use_lifetimes");
-    store.register_renamed("elided_lifetime_in_path", "elided_lifetimes_in_paths");
     store.register_renamed("bare_trait_object", "bare_trait_objects");
     store.register_renamed("unstable_name_collision", "unstable_name_collisions");
     store.register_renamed("unused_doc_comment", "unused_doc_comments");
     store.register_renamed("unknown_features", "unused_features");
+    // Yes, it got renamed twice :'(
+    store.register_renamed("elided_lifetime_in_path", "hidden_lifetimes_in_types");
+    store.register_renamed("elided_lifetimes_in_paths", "hidden_lifetimes_in_types");
+
     store.register_removed("unsigned_negation", "replaced by negate_unsigned feature gate");
     store.register_removed("negate_unsigned", "cast a signed value instead");
     store.register_removed("raw_pointer_derive", "using derive with raw pointers is ok");

src/test/ui/in-band-lifetimes/elided-lifetimes.fixed renamed to src/test/ui/lint/hidden-lifetimes-in-types.fixed

@@ -12,7 +12,7 @@
 // compile-flags: --edition 2018
 
 #![allow(unused)]
-#![deny(elided_lifetimes_in_paths)]
+#![deny(hidden_lifetimes_in_types)]
 //~^ NOTE lint level defined here
 
 use std::cell::{RefCell, Ref};
@@ -21,7 +21,7 @@ use std::cell::{RefCell, Ref};
 struct Foo<'a> { x: &'a u32 }
 
 fn foo(x: &Foo<'_>) {
-    //~^ ERROR implicit lifetime parameters in types are deprecated
+    //~^ ERROR hidden lifetime parameters in types are deprecated
     //~| HELP indicate the anonymous lifetime
 }
 
@@ -35,13 +35,13 @@ struct WrappedWithBow<'a> {
 }
 
 fn wrap_gift(gift: &str) -> Wrapped<'_> {
-    //~^ ERROR implicit lifetime parameters in types are deprecated
+    //~^ ERROR hidden lifetime parameters in types are deprecated
     //~| HELP indicate the anonymous lifetime
     Wrapped(gift)
 }
 
 fn wrap_gift_with_bow(gift: &str) -> WrappedWithBow<'_> {
-    //~^ ERROR implicit lifetime parameters in types are deprecated
+    //~^ ERROR hidden lifetime parameters in types are deprecated
     //~| HELP indicate the anonymous lifetime
     WrappedWithBow { gift }
 }
@@ -53,7 +53,7 @@ macro_rules! autowrapper {
         }
 
         fn $fn_name(gift: &str) -> $type_name<'_> {
-            //~^ ERROR implicit lifetime parameters in types are deprecated
+            //~^ ERROR hidden lifetime parameters in types are deprecated
             //~| HELP indicate the anonymous lifetime
             $type_name { gift }
         }
@@ -67,15 +67,15 @@ autowrapper!(Autowrapped, autowrap_gift, 'a);
 macro_rules! anytuple_ref_ty {
     ($($types:ty),*) => {
         Ref<'_, ($($types),*)>
-        //~^ ERROR implicit lifetime parameters in types are deprecated
+        //~^ ERROR hidden lifetime parameters in types are deprecated
         //~| HELP indicate the anonymous lifetime
     }
 }
 
 fn main() {
     let honesty = RefCell::new((4, 'e'));
     let loyalty: Ref<'_, (u32, char)> = honesty.borrow();
-    //~^ ERROR implicit lifetime parameters in types are deprecated
+    //~^ ERROR hidden lifetime parameters in types are deprecated
     //~| HELP indicate the anonymous lifetime
     let generosity = Ref::map(loyalty, |t| &t.0);
 

src/test/ui/in-band-lifetimes/elided-lifetimes.rs renamed to src/test/ui/lint/hidden-lifetimes-in-types.rs

@@ -12,7 +12,7 @@
 // compile-flags: --edition 2018
 
 #![allow(unused)]
-#![deny(elided_lifetimes_in_paths)]
+#![deny(hidden_lifetimes_in_types)]
 //~^ NOTE lint level defined here
 
 use std::cell::{RefCell, Ref};
@@ -21,7 +21,7 @@ use std::cell::{RefCell, Ref};
 struct Foo<'a> { x: &'a u32 }
 
 fn foo(x: &Foo) {
-    //~^ ERROR implicit lifetime parameters in types are deprecated
+    //~^ ERROR hidden lifetime parameters in types are deprecated
     //~| HELP indicate the anonymous lifetime
 }
 
@@ -35,13 +35,13 @@ struct WrappedWithBow<'a> {
 }
 
 fn wrap_gift(gift: &str) -> Wrapped {
-    //~^ ERROR implicit lifetime parameters in types are deprecated
+    //~^ ERROR hidden lifetime parameters in types are deprecated
     //~| HELP indicate the anonymous lifetime
     Wrapped(gift)
 }
 
 fn wrap_gift_with_bow(gift: &str) -> WrappedWithBow {
-    //~^ ERROR implicit lifetime parameters in types are deprecated
+    //~^ ERROR hidden lifetime parameters in types are deprecated
     //~| HELP indicate the anonymous lifetime
     WrappedWithBow { gift }
 }
@@ -53,7 +53,7 @@ macro_rules! autowrapper {
         }
 
         fn $fn_name(gift: &str) -> $type_name {
-            //~^ ERROR implicit lifetime parameters in types are deprecated
+            //~^ ERROR hidden lifetime parameters in types are deprecated
             //~| HELP indicate the anonymous lifetime
             $type_name { gift }
         }
@@ -67,15 +67,15 @@ autowrapper!(Autowrapped, autowrap_gift, 'a);
 macro_rules! anytuple_ref_ty {
     ($($types:ty),*) => {
         Ref<($($types),*)>
-        //~^ ERROR implicit lifetime parameters in types are deprecated
+        //~^ ERROR hidden lifetime parameters in types are deprecated
         //~| HELP indicate the anonymous lifetime
     }
 }
 
 fn main() {
     let honesty = RefCell::new((4, 'e'));
     let loyalty: Ref<(u32, char)> = honesty.borrow();
-    //~^ ERROR implicit lifetime parameters in types are deprecated
+    //~^ ERROR hidden lifetime parameters in types are deprecated
     //~| HELP indicate the anonymous lifetime
     let generosity = Ref::map(loyalty, |t| &t.0);
 

src/test/ui/in-band-lifetimes/elided-lifetimes.stderr renamed to src/test/ui/lint/hidden-lifetimes-in-types.stderr

@@ -1,44 +1,44 @@
-error: implicit lifetime parameters in types are deprecated
-  --> $DIR/elided-lifetimes.rs:23:12
+error: hidden lifetime parameters in types are deprecated
+  --> $DIR/hidden-lifetimes-in-types.rs:23:12
    |
 LL | fn foo(x: &Foo) {
    |            ^^^- help: indicate the anonymous lifetime: `<'_>`
    |
 note: lint level defined here
-  --> $DIR/elided-lifetimes.rs:15:9
+  --> $DIR/hidden-lifetimes-in-types.rs:15:9
    |
-LL | #![deny(elided_lifetimes_in_paths)]
+LL | #![deny(hidden_lifetimes_in_types)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: implicit lifetime parameters in types are deprecated
-  --> $DIR/elided-lifetimes.rs:37:29
+error: hidden lifetime parameters in types are deprecated
+  --> $DIR/hidden-lifetimes-in-types.rs:37:29
    |
 LL | fn wrap_gift(gift: &str) -> Wrapped {
    |                             ^^^^^^^- help: indicate the anonymous lifetime: `<'_>`
 
-error: implicit lifetime parameters in types are deprecated
-  --> $DIR/elided-lifetimes.rs:43:38
+error: hidden lifetime parameters in types are deprecated
+  --> $DIR/hidden-lifetimes-in-types.rs:43:38
    |
 LL | fn wrap_gift_with_bow(gift: &str) -> WrappedWithBow {
    |                                      ^^^^^^^^^^^^^^- help: indicate the anonymous lifetime: `<'_>`
 
-error: implicit lifetime parameters in types are deprecated
-  --> $DIR/elided-lifetimes.rs:77:18
+error: hidden lifetime parameters in types are deprecated
+  --> $DIR/hidden-lifetimes-in-types.rs:77:18
    |
 LL |     let loyalty: Ref<(u32, char)> = honesty.borrow();
    |                  ^^^^^^^^^^^^^^^^ help: indicate the anonymous lifetime: `Ref<'_, (u32, char)>`
 
-error: implicit lifetime parameters in types are deprecated
-  --> $DIR/elided-lifetimes.rs:69:9
+error: hidden lifetime parameters in types are deprecated
+  --> $DIR/hidden-lifetimes-in-types.rs:69:9
    |
 LL |         Ref<($($types),*)>
    |         ^^^^^^^^^^^^^^^^^^ help: indicate the anonymous lifetime: `Ref<'_, ($($types),*)>`
 ...
 LL |     let yellow: anytuple_ref_ty!(bool, &str) = laughter.borrow();
    |                 ---------------------------- in this macro invocation
 
-error: implicit lifetime parameters in types are deprecated
-  --> $DIR/elided-lifetimes.rs:55:36
+error: hidden lifetime parameters in types are deprecated
+  --> $DIR/hidden-lifetimes-in-types.rs:55:36
    |
 LL |         fn $fn_name(gift: &str) -> $type_name {
    |                                    ^^^^^^^^^^- help: indicate the anonymous lifetime: `<'_>`