Always check if the SVH of rlib and dylibs matches other crate sources

If a crate is both an rlib and cdylib, the metadata loader would
previously incorrectly assume that it is possible to link against the
cdylib. Cdylibs don't export all symbols required for linking as rust
library.

Possibly fixes issue number 82151

Author: bjorn3

compiler/rustc_metadata/src/locator.rs

@@ -503,9 +503,8 @@ impl<'a> CrateLocator<'a> {
     // the errors and notes are emitted about the set of libraries.
     //
     // With only one library in the set, this function will extract it, and then
-    // read the metadata from it if `*slot` is `None`. If the metadata couldn't
-    // be read, it is assumed that the file isn't a valid rust library (no
-    // errors are emitted).
+    // read the metadata from it. If the metadata couldn't be read, it is assumed
+    // that the file isn't a valid rust library (no errors are emitted).
     fn extract_one(
         &mut self,
         m: FxHashMap<PathBuf, PathKind>,
@@ -521,17 +520,8 @@ impl<'a> CrateLocator<'a> {
         //
         // See also #68149 which provides more detail on why emitting the
         // dependency on the rlib is a bad thing.
-        //
-        // We currently do not verify that these other sources are even in sync,
-        // and this is arguably a bug (see #10786), but because reading metadata
-        // is quite slow (especially from dylibs) we currently do not read it
-        // from the other crate sources.
-        if slot.is_some() {
-            if m.is_empty() || !self.needs_crate_flavor(flavor) {
-                return Ok(None);
-            } else if m.len() == 1 {
-                return Ok(Some(m.into_iter().next().unwrap()));
-            }
+        if slot.is_some() && !self.needs_crate_flavor(flavor) {
+            return Ok(None);
         }
 
         let mut ret: Option<(PathBuf, PathKind)> = None;