rustc_lint: Remove lint `plugin_as_library`

src/doc/rustc/src/lints/listing/warn-by-default.md

@@ -307,18 +307,6 @@ warning: path statement with no effect
   |
 ```
 
-## plugin-as-library
-
-This lint detects when compiler plugins are used as ordinary library in
-non-plugin crate. Some example code that triggers this lint:
-
-```rust,ignore
-#![feature(plugin)]
-#![plugin(macro_crate_test)]
-
-extern crate macro_crate_test;
-```
-
 ## private-in-public
 
 This lint detects private items in public interfaces not caught by the old implementation. Some

src/doc/unstable-book/src/language-features/plugin.md

@@ -24,8 +24,7 @@ mechanics of defining and loading a plugin.
 In the vast majority of cases, a plugin should *only* be used through
 `#![plugin]` and not through an `extern crate` item.  Linking a plugin would
 pull in all of libsyntax and librustc as dependencies of your crate.  This is
-generally unwanted unless you are building another plugin.  The
-`plugin_as_library` lint checks these guidelines.
+generally unwanted unless you are building another plugin.
 
 The usual practice is to put compiler plugins in their own crate, separate from
 any `macro_rules!` macros or ordinary Rust code meant to be used by consumers

src/librustc_lint/builtin.rs

@@ -24,7 +24,7 @@
 use std::fmt::Write;
 
 use rustc::hir::def::{Res, DefKind};
-use rustc::hir::def_id::{DefId, LOCAL_CRATE};
+use rustc::hir::def_id::DefId;
 use rustc::ty::{self, Ty, TyCtxt, layout::VariantIdx};
 use rustc::{lint, util};
 use rustc::lint::FutureIncompatibleInfo;
@@ -800,45 +800,6 @@ impl EarlyLintPass for UnusedDocComment {
     }
 }
 
-declare_lint! {
-    PLUGIN_AS_LIBRARY,
-    Warn,
-    "compiler plugin used as ordinary library in non-plugin crate"
-}
-
-declare_lint_pass!(PluginAsLibrary => [PLUGIN_AS_LIBRARY]);
-
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for PluginAsLibrary {
-    fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item) {
-        if cx.tcx.plugin_registrar_fn(LOCAL_CRATE).is_some() {
-            // We're compiling a plugin; it's fine to link other plugins.
-            return;
-        }
-
-        match it.kind {
-            hir::ItemKind::ExternCrate(..) => (),
-            _ => return,
-        };
-
-        let def_id = cx.tcx.hir().local_def_id(it.hir_id);
-        let prfn = match cx.tcx.extern_mod_stmt_cnum(def_id) {
-            Some(cnum) => cx.tcx.plugin_registrar_fn(cnum),
-            None => {
-                // Probably means we aren't linking the crate for some reason.
-                //
-                // Not sure if / when this could happen.
-                return;
-            }
-        };
-
-        if prfn.is_some() {
-            cx.span_lint(PLUGIN_AS_LIBRARY,
-                         it.span,
-                         "compiler plugin used as an ordinary library");
-        }
-    }
-}
-
 declare_lint! {
     NO_MANGLE_CONST_ITEMS,
     Deny,
@@ -1268,7 +1229,6 @@ declare_lint_pass!(
         MISSING_DEBUG_IMPLEMENTATIONS,
         ANONYMOUS_PARAMETERS,
         UNUSED_DOC_COMMENTS,
-        PLUGIN_AS_LIBRARY,
         NO_MANGLE_CONST_ITEMS,
         NO_MANGLE_GENERIC_ITEMS,
         MUTABLE_TRANSMUTES,

src/librustc_lint/lib.rs

@@ -157,8 +157,6 @@ macro_rules! late_lint_mod_passes {
             // Depends on types used in type definitions
             MissingCopyImplementations: MissingCopyImplementations,
 
-            PluginAsLibrary: PluginAsLibrary,
-
             // Depends on referenced function signatures in expressions
             MutableTransmutes: MutableTransmutes,
 
@@ -350,6 +348,7 @@ fn register_builtins(store: &mut lint::LintStore, no_interleave_lints: bool) {
         "converted into hard error, see https://github.com/rust-lang/rust/issues/35896");
     store.register_removed("nested_impl_trait",
         "converted into hard error, see https://github.com/rust-lang/rust/issues/59014");
+    store.register_removed("plugin_as_library", "plugins have been deprecated and retired");
 }
 
 fn register_internals(store: &mut lint::LintStore) {

src/test/ui-fulldeps/macro-crate-multi-decorator.rs

@@ -1,9 +1,4 @@
-// run-pass
-
-#![allow(plugin_as_library)]
-#![allow(dead_code)]
-#![allow(unused_variables)]
-#![allow(unused_imports)]
+// check-pass
 // aux-build:macro-crate-test.rs
 // ignore-stage1
 

src/test/ui-fulldeps/plugin-as-extern-crate.rs

@@ -1,11 +1,10 @@
+// check-pass
 // aux-build:empty-plugin.rs
 // ignore-cross-compile
 //
 // empty_plugin will not compile on a cross-compiled target because
 // libsyntax is not compiled for it.
 
-#![deny(plugin_as_library)]
+extern crate empty_plugin; // OK, plugin crates are still crates
 
-extern crate empty_plugin; //~ ERROR compiler plugin used as an ordinary library
-
-fn main() { }
+fn main() {}