Auto merge of #29148 - petrochenkov:noshow, r=alexcrichton

Closes https://github.com/rust-lang/rust/issues/29145

[breaking-change], needs a crater run.

src/test/run-pass/arr_cycle.rs

@@ -10,7 +10,7 @@
 
 use std::cell::Cell;
 
-#[derive(Show)]
+#[derive(Debug)]
 struct B<'a> {
     a: [Cell<Option<&'a B<'a>>>; 2]
 }

src/test/run-pass/const-adt-align-mismatch.rs

@@ -10,7 +10,7 @@
 
 use std::mem;
 
-#[derive(PartialEq, Show)]
+#[derive(PartialEq, Debug)]
 enum Foo {
     A(u32),
     Bar([u16; 4]),

src/test/run-pass/deprecated-derive.rs

@@ -8,8 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#[derive(Show)]
-//~^ WARNING derive(Show) is deprecated
+#![feature(rustc_private)]
+
+extern crate serialize;
+
+#[derive(Encodable)]
+//~^ WARNING derive(Encodable) is deprecated in favor of derive(RustcEncodable)
 struct Test1;
 
 fn main() { }

src/test/run-pass/vec_cycle.rs

@@ -10,7 +10,7 @@
 
 use std::cell::Cell;
 
-#[derive(Show)]
+#[derive(Debug)]
 struct C<'a> {
     v: Vec<Cell<Option<&'a C<'a>>>>,
 }

src/test/run-pass/vec_cycle_wrapped.rs

@@ -10,12 +10,12 @@
 
 use std::cell::Cell;
 
-#[derive(Show)]
+#[derive(Debug)]
 struct Refs<'a> {
     v: Vec<Cell<Option<&'a C<'a>>>>,
 }
 
-#[derive(Show)]
+#[derive(Debug)]
 struct C<'a> {
     refs: Refs<'a>,
 }