fix invalid_ref lint and prepare for invalid_value lint

Author: RalfJung

Diff for: clippy_lints/src/invalid_ref.rs

@@ -21,9 +21,10 @@ declare_clippy_lint! {
     "creation of invalid reference"
 }
 
-const ZERO_REF_SUMMARY: &str = "reference to zeroed memory";
-const UNINIT_REF_SUMMARY: &str = "reference to uninitialized memory";
-const HELP: &str = "Creation of a null reference is undefined behavior; \
+const SUMMARY: &str = "invalid reference";
+const ZERO_REF_HELP: &str = "Creation of a null reference is undefined behavior; \
+                    see https://doc.rust-lang.org/reference/behavior-considered-undefined.html";
+const UNINIT_REF_HELP: &str = "Creation of an uninitialized reference is undefined behavior; \
                     see https://doc.rust-lang.org/reference/behavior-considered-undefined.html";
 
 declare_lint_pass!(InvalidRef => [INVALID_REF]);
@@ -37,18 +38,18 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidRef {
             if let ty::Ref(..) = cx.tables.expr_ty(expr).sty;
             if let Some(def_id) = cx.tables.qpath_res(qpath, path.hir_id).opt_def_id();
             then {
-                let msg = if match_def_path(cx, def_id, &paths::MEM_ZEROED) |
+                let help = if match_def_path(cx, def_id, &paths::MEM_ZEROED) |
                              match_def_path(cx, def_id, &paths::INIT)
                 {
-                    ZERO_REF_SUMMARY
+                    ZERO_REF_HELP
                 } else if match_def_path(cx, def_id, &paths::MEM_UNINIT) |
                           match_def_path(cx, def_id, &paths::UNINIT)
                 {
-                    UNINIT_REF_SUMMARY
+                    UNINIT_REF_HELP
                 } else {
                     return;
                 };
-                span_help_and_lint(cx, INVALID_REF, expr.span, msg, HELP);
+                span_help_and_lint(cx, INVALID_REF, expr.span, SUMMARY, help);
             }
         }
     }

Diff for: tests/ui/invalid_ref.rs

@@ -1,4 +1,4 @@
-#![allow(deprecated, unused)]
+#![allow(deprecated, unused, unknown_lints, invalid_value)]
 #![feature(core_intrinsics)]
 
 extern crate core;

Diff for: tests/ui/invalid_ref.stderr

@@ -1,4 +1,4 @@
-error: reference to zeroed memory
+error: invalid reference
   --> $DIR/invalid_ref.rs:23:24
    |
 LL |     let ref_zero: &T = std::mem::zeroed(); // warning
@@ -7,37 +7,37 @@ LL |     let ref_zero: &T = std::mem::zeroed(); // warning
    = note: `#[deny(clippy::invalid_ref)]` on by default
    = help: Creation of a null reference is undefined behavior; see https://doc.rust-lang.org/reference/behavior-considered-undefined.html
 
-error: reference to zeroed memory
+error: invalid reference
   --> $DIR/invalid_ref.rs:27:24
    |
 LL |     let ref_zero: &T = core::mem::zeroed(); // warning
    |                        ^^^^^^^^^^^^^^^^^^^
    |
    = help: Creation of a null reference is undefined behavior; see https://doc.rust-lang.org/reference/behavior-considered-undefined.html
 
-error: reference to zeroed memory
+error: invalid reference
   --> $DIR/invalid_ref.rs:31:24
    |
 LL |     let ref_zero: &T = std::intrinsics::init(); // warning
    |                        ^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: Creation of a null reference is undefined behavior; see https://doc.rust-lang.org/reference/behavior-considered-undefined.html
 
-error: reference to uninitialized memory
+error: invalid reference
   --> $DIR/invalid_ref.rs:35:26
    |
 LL |     let ref_uninit: &T = std::mem::uninitialized(); // warning
    |                          ^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: Creation of a null reference is undefined behavior; see https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+   = help: Creation of an uninitialized reference is undefined behavior; see https://doc.rust-lang.org/reference/behavior-considered-undefined.html
 
-error: reference to uninitialized memory
+error: invalid reference
   --> $DIR/invalid_ref.rs:39:26
    |
 LL |     let ref_uninit: &T = core::mem::uninitialized(); // warning
    |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: Creation of a null reference is undefined behavior; see https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+   = help: Creation of an uninitialized reference is undefined behavior; see https://doc.rust-lang.org/reference/behavior-considered-undefined.html
 
 error: aborting due to 5 previous errors