Make sure that all upstream generics get re-exported from Rust dylibs.

3 files changed, 38 insertions, 9 deletions

diff --git a/src/librustc_codegen_ssa/back/linker.rs b/src/librustc_codegen_ssa/back/linker.rs
index 11f5d3007e6..4679f650133 100644
--- a/src/librustc_codegen_ssa/back/linker.rs
+++ b/src/librustc_codegen_ssa/back/linker.rs
@@ -1103,7 +1103,11 @@ fn exported_symbols(tcx: TyCtxt<'_>, crate_type: CrateType) -> Vec<String> {
     let export_threshold = symbol_export::crates_export_threshold(&[crate_type]);
     for &(symbol, level) in tcx.exported_symbols(LOCAL_CRATE).iter() {
         if level.is_below_threshold(export_threshold) {
-            symbols.push(symbol.symbol_name(tcx).to_string());
+            symbols.push(symbol_export::symbol_name_for_instance_in_crate(
+                tcx,
+                symbol,
+                LOCAL_CRATE,
+            ));
         }
     }
 
@@ -1124,12 +1128,7 @@ fn exported_symbols(tcx: TyCtxt<'_>, crate_type: CrateType) -> Vec<String> {
                     continue;
                 }
 
-                // FIXME rust-lang/rust#64319, rust-lang/rust#64872:
-                // We want to block export of generics from dylibs,
-                // but we must fix rust-lang/rust#65890 before we can
-                // do that robustly.
-
-                symbols.push(symbol.symbol_name(tcx).to_string());
+                symbols.push(symbol_export::symbol_name_for_instance_in_crate(tcx, symbol, cnum));
             }
         }
     }
diff --git a/src/librustc_codegen_ssa/back/symbol_export.rs b/src/librustc_codegen_ssa/back/symbol_export.rs
index a406b5f103b..bd44b4a38fd 100644
--- a/src/librustc_codegen_ssa/back/symbol_export.rs
+++ b/src/librustc_codegen_ssa/back/symbol_export.rs
@@ -8,6 +8,7 @@ use rustc::ty::query::Providers;
 use rustc::ty::subst::SubstsRef;
 use rustc::ty::Instance;
 use rustc::ty::{SymbolName, TyCtxt};
+use rustc_codegen_utils::symbol_names;
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir as hir;
@@ -358,3 +359,32 @@ fn symbol_export_level(tcx: TyCtxt<'_>, sym_def_id: DefId) -> SymbolExportLevel
         SymbolExportLevel::Rust
     }
 }
+
+/// This is the symbol name of the given instance instantiated in a specific crate.
+pub fn symbol_name_for_instance_in_crate<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    symbol: ExportedSymbol<'tcx>,
+    instantiating_crate: CrateNum,
+) -> String {
+    // If this is something instantiated in the local crate then we might
+    // already have cached the name as a query result.
+    if instantiating_crate == LOCAL_CRATE {
+        return symbol.symbol_name_for_local_instance(tcx).to_string();
+    }
+
+    // This is something instantiated in an upstream crate, so we have to use
+    // the slower (because uncached) version of computing the symbol name.
+    match symbol {
+        ExportedSymbol::NonGeneric(def_id) => symbol_names::symbol_name_for_instance_in_crate(
+            tcx,
+            Instance::mono(tcx, def_id),
+            instantiating_crate,
+        ),
+        ExportedSymbol::Generic(def_id, substs) => symbol_names::symbol_name_for_instance_in_crate(
+            tcx,
+            Instance::new(def_id, substs),
+            instantiating_crate,
+        ),
+        ExportedSymbol::NoDefId(symbol_name) => symbol_name.to_string(),
+    }
+}
diff --git a/src/librustc_codegen_ssa/back/write.rs b/src/librustc_codegen_ssa/back/write.rs
index 801bfdea70d..049faff7c49 100644
--- a/src/librustc_codegen_ssa/back/write.rs
+++ b/src/librustc_codegen_ssa/back/write.rs
@@ -2,7 +2,7 @@ use super::command::Command;
 use super::link::{self, get_linker, remove};
 use super::linker::LinkerInfo;
 use super::lto::{self, SerializedModule};
-use super::symbol_export::ExportedSymbols;
+use super::symbol_export::{symbol_name_for_instance_in_crate, ExportedSymbols};
 use crate::{
     CachedModuleCodegen, CodegenResults, CompiledModule, CrateInfo, ModuleCodegen, ModuleKind,
     RLIB_BYTECODE_EXTENSION,
@@ -956,7 +956,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
             let symbols = tcx
                 .exported_symbols(cnum)
                 .iter()
-                .map(|&(s, lvl)| (s.symbol_name(tcx).to_string(), lvl))
+                .map(|&(s, lvl)| (symbol_name_for_instance_in_crate(tcx, s, cnum), lvl))
                 .collect();
             Arc::new(symbols)
         };