[Debug info] Map the thrown error type into context when generating debug info

Author: DougGregor

lib/IRGen/IRGenDebugInfo.cpp

@@ -2570,11 +2570,18 @@ IRGenDebugInfoImpl::emitFunction(const SILDebugScope *DS, llvm::Function *Fn,
   if (FnTy && (Opts.DebugInfoLevel > IRGenDebugInfoLevel::LineTables))
     if (auto ErrorInfo = FnTy->getOptionalErrorResult()) {
       GenericContextScope scope(IGM, FnTy->getInvocationGenericSignature());
+      CanType errorResultTy = ErrorInfo->getReturnValueType(
+          IGM.getSILModule(), FnTy,
+          IGM.getMaximalTypeExpansionContext());
       SILType SILTy = IGM.silConv.getSILType(
           *ErrorInfo, FnTy, IGM.getMaximalTypeExpansionContext());
+
+      errorResultTy = SILFn->mapTypeIntoContext(errorResultTy)
+          ->getCanonicalType();
+      SILTy = SILFn->mapTypeIntoContext(SILTy);
+
       auto DTI = DebugTypeInfo::getFromTypeInfo(
-          ErrorInfo->getReturnValueType(IGM.getSILModule(), FnTy,
-                                        IGM.getMaximalTypeExpansionContext()),
+          errorResultTy,
           IGM.getTypeInfo(SILTy), IGM, false);
       Error = DBuilder.getOrCreateArray({getOrCreateType(DTI)}).get();
     }

test/DebugInfo/Errors.swift

@@ -26,6 +26,17 @@ public class C {
     }
 }
 
+// Function with typed throws.
+// CHECK: !DISubprogram(name: "genericRethrow", {{.*}}thrownTypes: ![[GENERIC_THROWN:.*]])
+// CHECK: ![[GENERIC_THROWN]] = !{![[GENERIC_THROWN_INNER:.*]]}
+// CHECK: ![[GENERIC_THROWN_INNER]] = !DICompositeType(tag: DW_TAG_structure_type, name: "$sxD", {{.*}}, elements: ![[GENERIC_THROWN_ELEMENTS:.*]], runtimeLang: DW_LANG_Swift)
+// CHECK: ![[GENERIC_THROWN_ELEMENTS]] = !{![[GENERIC_THROWN_ELEMENTS_INNER:.*]]}
+// CHECK: ![[GENERIC_THROWN_ELEMENTS_INNER]] = !DIDerivedType(tag: DW_TAG_inheritance, {{.*}}baseType: ![[GENERIC_THROWN_BASE:.*]], extraData: {{.*}})
+// CHECK: ![[GENERIC_THROWN_BASE]] = !DICompositeType(tag: DW_TAG_structure_type, name: "$ss5Error_pmD", size: {{.*}}, flags: DIFlagArtificial, runtimeLang: DW_LANG_Swift, identifier: "$ss5Error_pmD")
+public func genericRethrow<E: Error>(fn: () throws(E) -> Void) throws(E) {
+  try fn()
+}
+
 // Negative tests.
 // CHECK: !DISubprogram(name: "returnThrowing",
 // CHECK-NOT:           thrownTypes: