Rollup merge of #105860 - Ezrashaw:add-long-errors-0460-0457, r=jruderman,GuillaumeGomez

Add long error docs for `E0460` and `E0457`

Final docs for errors in #61137 that have UI tests, my next PRs will also add these tests.

r? ``@GuillaumeGomez``

compiler/rustc_error_codes/src/error_codes.rs

@@ -239,8 +239,10 @@ E0452: include_str!("./error_codes/E0452.md"),
 E0453: include_str!("./error_codes/E0453.md"),
 E0454: include_str!("./error_codes/E0454.md"),
 E0455: include_str!("./error_codes/E0455.md"),
+E0457: include_str!("./error_codes/E0457.md"),
 E0458: include_str!("./error_codes/E0458.md"),
 E0459: include_str!("./error_codes/E0459.md"),
+E0460: include_str!("./error_codes/E0460.md"),
 E0463: include_str!("./error_codes/E0463.md"),
 E0464: include_str!("./error_codes/E0464.md"),
 E0466: include_str!("./error_codes/E0466.md"),
@@ -592,8 +594,6 @@ E0791: include_str!("./error_codes/E0791.md"),
 //  E0421, // merged into 531
 //  E0427, // merged into 530
 //  E0456, // plugin `..` is not available for triple `..`
-    E0457, // plugin `..` only found in rlib format, but must be available...
-    E0460, // found possibly newer version of crate `..`
     E0461, // couldn't find crate `..` with expected target triple ..
     E0462, // found staticlib `..` instead of rlib or dylib
     E0465, // multiple .. candidates for `..` found

compiler/rustc_error_codes/src/error_codes/E0457.md

@@ -0,0 +1,36 @@
+Plugin `..` only found in rlib format, but must be available in dylib format.
+
+Erroronous code example:
+
+`rlib-plugin.rs`
+```ignore (needs-linkage-with-other-tests)
+#![crate_type = "rlib"]
+#![feature(rustc_private)]
+
+extern crate rustc_middle;
+extern crate rustc_driver;
+
+use rustc_driver::plugin::Registry;
+
+#[no_mangle]
+fn __rustc_plugin_registrar(_: &mut Registry) {}
+```
+
+`main.rs`
+```ignore (needs-linkage-with-other-tests)
+#![feature(plugin)]
+#![plugin(rlib_plugin)] // error: plugin `rlib_plugin` only found in rlib
+                        //        format, but must be available in dylib
+
+fn main() {}
+```
+
+The compiler exposes a plugin interface to allow altering the compile process
+(adding lints, etc). Plugins must be defined in their own crates (similar to
+[proc-macro](../reference/procedural-macros.html) isolation) and then compiled
+and linked to another crate. Plugin crates *must* be compiled to the
+dynamically-linked dylib format, and not the statically-linked rlib format.
+Learn more about different output types in
+[this section](../reference/linkage.html) of the Rust reference.
+
+This error is easily fixed by recompiling the plugin crate in the dylib format.

compiler/rustc_error_codes/src/error_codes/E0460.md

@@ -0,0 +1,71 @@
+Found possibly newer version of crate `..` which `..` depends on.
+
+Consider these erroneous files:
+
+`a1.rs`
+```ignore (needs-linkage-with-other-tests)
+#![crate_name = "a"]
+
+pub fn foo<T>() {}
+```
+
+`a2.rs`
+```ignore (needs-linkage-with-other-tests)
+#![crate_name = "a"]
+
+pub fn foo<T>() {
+    println!("foo<T>()");
+}
+```
+
+`b.rs`
+```ignore (needs-linkage-with-other-tests)
+#![crate_name = "b"]
+
+extern crate a; // linked with `a1.rs`
+
+pub fn foo() {
+    a::foo::<isize>();
+}
+```
+
+`main.rs`
+```ignore (needs-linkage-with-other-tests)
+extern crate a; // linked with `a2.rs`
+extern crate b; // error: found possibly newer version of crate `a` which `b`
+                //        depends on
+
+fn main() {}
+```
+
+The dependency graph of this program can be represented as follows:
+```text
+    crate `main`
+         |
+         +-------------+
+         |             |
+         |             v
+depends: |         crate `b`
+ `a` v1  |             |
+         |             | depends:
+         |             |  `a` v2
+         v             |
+      crate `a` <------+
+```
+
+Crate `main` depends on crate `a` (version 1) and crate `b` which in turn
+depends on crate `a` (version 2); this discrepancy in versions cannot be
+reconciled. This difference in versions typically occurs when one crate is
+compiled and linked, then updated and linked to another crate. The crate
+"version" is a SVH (Strict Version Hash) of the crate in an
+implementation-specific way. Note that this error can *only* occur when
+directly compiling and linking with `rustc`; [Cargo] automatically resolves
+dependencies, without using the compiler's own dependency management that
+causes this issue.
+
+This error can be fixed by:
+ * Using [Cargo], the Rust package manager, automatically fixing this issue.
+ * Recompiling crate `a` so that both crate `b` and `main` have a uniform
+   version to depend on.
+
+[Cargo]: ../cargo/index.html