Add compiler error E0523 long description and test

compiler/rustc_error_codes/src/error_codes.rs

@@ -286,6 +286,7 @@ E0519: include_str!("./error_codes/E0519.md"),
 E0520: include_str!("./error_codes/E0520.md"),
 E0521: include_str!("./error_codes/E0521.md"),
 E0522: include_str!("./error_codes/E0522.md"),
+E0523: include_str!("./error_codes/E0523.md"),
 E0524: include_str!("./error_codes/E0524.md"),
 E0525: include_str!("./error_codes/E0525.md"),
 E0527: include_str!("./error_codes/E0527.md"),
@@ -622,7 +623,6 @@ E0793: include_str!("./error_codes/E0793.md"),
 //  E0488, // lifetime of variable does not enclose its declaration
 //  E0489, // type/lifetime parameter not in scope here
 //  E0490, // removed: unreachable
-    E0523, // two dependencies have same (crate-name, disambiguator) but different SVH
 //  E0526, // shuffle indices are not constant
 //  E0540, // multiple rustc_deprecated attributes
 //  E0548, // replaced with a generic attribute input check

compiler/rustc_error_codes/src/error_codes/E0464.md

@@ -1,6 +1,21 @@
 The compiler found multiple library files with the requested crate name.
 
+```compile_fail
+// aux-build:crateresolve-1.rs
+// aux-build:crateresolve-2.rs
+// aux-build:crateresolve-3.rs
+
+extern crate crateresolve;
+//~^ ERROR multiple candidates for `rlib` dependency `crateresolve` found
+
+fn main() {}
+```
+
 This error can occur in several different cases -- for example, when using
 `extern crate` or passing `--extern` options without crate paths. It can also be
 caused by caching issues with the build directory, in which case `cargo clean`
 may help.
+
+In the above example, there are three different library files, all of which
+define the same crate name. Without providing a full path, there is no way for
+the compiler to know which crate it should use.

compiler/rustc_error_codes/src/error_codes/E0523.md

@@ -0,0 +1,25 @@
+#### Note: this error code is no longer emitted by the compiler.
+
+The compiler found multiple library files with the requested crate name.
+
+```compile_fail
+// aux-build:crateresolve-1.rs
+// aux-build:crateresolve-2.rs
+// aux-build:crateresolve-3.rs
+
+extern crate crateresolve;
+//~^ ERROR multiple candidates for `rlib` dependency `crateresolve` found
+
+fn main() {}
+```
+
+This error can occur in several different cases -- for example, when using
+`extern crate` or passing `--extern` options without crate paths. It can also be
+caused by caching issues with the build directory, in which case `cargo clean`
+may help.
+
+In the above example, there are three different library files, all of which
+define the same crate name. Without providing a full path, there is no way for
+the compiler to know which crate it should use.
+
+*Note that E0523 has been merged into E0464.*

compiler/rustc_metadata/src/creader.rs

@@ -356,7 +356,12 @@ impl<'a> CrateLoader<'a> {
         for (_, other) in self.cstore.iter_crate_data() {
             // Same stable crate id but different SVH
             if other.stable_crate_id() == root.stable_crate_id() && other.hash() != root.hash() {
-                return Err(CrateError::SymbolConflictsOthers(root.name()));
+                bug!(
+                    "Previously returned E0523 here. \
+                     See https://github.com/rust-lang/rust/pull/100599 for additional discussion.\
+                     root.name() = {}.",
+                    root.name()
+                );
             }
         }
 

compiler/rustc_metadata/src/errors.rs

@@ -511,14 +511,6 @@ pub struct SymbolConflictsCurrent {
     pub crate_name: Symbol,
 }
 
-#[derive(Diagnostic)]
-#[diag(metadata_symbol_conflicts_others, code = "E0523")]
-pub struct SymbolConflictsOthers {
-    #[primary_span]
-    pub span: Span,
-    pub crate_name: Symbol,
-}
-
 #[derive(Diagnostic)]
 #[diag(metadata_stable_crate_id_collision)]
 pub struct StableCrateIdCollision {

compiler/rustc_metadata/src/locator.rs

@@ -945,7 +945,6 @@ pub(crate) enum CrateError {
     ExternLocationNotFile(Symbol, PathBuf),
     MultipleCandidates(Symbol, CrateFlavor, Vec<PathBuf>),
     SymbolConflictsCurrent(Symbol),
-    SymbolConflictsOthers(Symbol),
     StableCrateIdCollision(Symbol, Symbol),
     DlOpen(String),
     DlSym(String),
@@ -989,9 +988,6 @@ impl CrateError {
             CrateError::SymbolConflictsCurrent(root_name) => {
                 sess.emit_err(errors::SymbolConflictsCurrent { span, crate_name: root_name });
             }
-            CrateError::SymbolConflictsOthers(root_name) => {
-                sess.emit_err(errors::SymbolConflictsOthers { span, crate_name: root_name });
-            }
             CrateError::StableCrateIdCollision(crate_name0, crate_name1) => {
                 sess.emit_err(errors::StableCrateIdCollision { span, crate_name0, crate_name1 });
             }

src/tools/tidy/src/error_codes.rs

@@ -31,7 +31,7 @@ const IGNORE_DOCTEST_CHECK: &[&str] = &["E0464", "E0570", "E0601", "E0602", "E06
 
 // Error codes that don't yet have a UI test. This list will eventually be removed.
 const IGNORE_UI_TEST_CHECK: &[&str] =
-    &["E0461", "E0465", "E0476", "E0514", "E0523", "E0554", "E0640", "E0717", "E0729"];
+    &["E0461", "E0465", "E0476", "E0514", "E0554", "E0640", "E0717", "E0729"];
 
 macro_rules! verbose_print {
     ($verbose:expr, $($fmt:tt)*) => {

tests/ui/error-codes/E0523.rs

@@ -0,0 +1,14 @@
+// aux-build:crateresolve1-1.rs
+// aux-build:crateresolve1-2.rs
+// aux-build:crateresolve1-3.rs
+
+// normalize-stderr-test: "\.nll/" -> "/"
+// normalize-stderr-test: "\\\?\\" -> ""
+// normalize-stderr-test: "(lib)?crateresolve1-([123])\.[a-z]+" -> "libcrateresolve1-$2.somelib"
+
+// NOTE: This test is duplicated from `tests/ui/crate-loading/crateresolve1.rs`.
+
+extern crate crateresolve1;
+//~^ ERROR multiple candidates for `rlib` dependency `crateresolve1` found
+
+fn main() {}

tests/ui/error-codes/E0523.stderr

@@ -0,0 +1,13 @@
+error[E0464]: multiple candidates for `rlib` dependency `crateresolve1` found
+  --> $DIR/E0523.rs:11:1
+   |
+LL | extern crate crateresolve1;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: candidate #1: $TEST_BUILD_DIR/error-codes/E0523/auxiliary/libcrateresolve1-1.somelib
+   = note: candidate #2: $TEST_BUILD_DIR/error-codes/E0523/auxiliary/libcrateresolve1-2.somelib
+   = note: candidate #3: $TEST_BUILD_DIR/error-codes/E0523/auxiliary/libcrateresolve1-3.somelib
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0464`.