Merge pull request #69758 from DougGregor/typed-throws-rethrows-cleanup

Typed throws rethrows cleanup

Author: DougGregor

lib/SILGen/SILGenApply.cpp

@@ -5728,6 +5728,8 @@ SILValue SILGenFunction::emitApplyWithRethrow(SILLocation loc, SILValue fn,
   {
     B.emitBlock(errorBB);
 
+    Scope scope(Cleanups, CleanupLocation(loc));
+
     // Grab the inner error.
     SILValue innerError;
     bool hasInnerIndirectError = fnConv.hasIndirectSILErrorResults();
@@ -5755,25 +5757,43 @@ SILValue SILGenFunction::emitApplyWithRethrow(SILLocation loc, SILValue fn,
       outerError = innerError;
     } else {
       // The error requires some kind of translation.
-
-      // Load the inner error, if it was returned indirectly.
-      if (innerError->getType().isAddress()) {
-        innerError = emitLoad(loc, innerError, getTypeLowering(innerErrorType),
-                              SGFContext(), IsTake).forward(*this);
-      }
+      outerErrorType = outerErrorType.getObjectType();
 
       // If we need to convert the error type, do so now.
       if (innerErrorType != outerErrorType) {
-        auto conversion = Conversion::getOrigToSubst(
-            AbstractionPattern(innerErrorType.getASTType()),
-            outerErrorType.getASTType(),
-            outerErrorType);
-        outerError = emitConvertedRValue(loc, conversion, SGFContext(),
-            [innerError](SILGenFunction &SGF, SILLocation loc, SGFContext C) {
-              return ManagedValue::forForwardedRValue(SGF, innerError);
+        assert(outerErrorType == SILType::getExceptionType(getASTContext()));
+
+        ProtocolConformanceRef conformances[1] = {
+          getModule().getSwiftModule()->conformsToProtocol(
+            innerError->getType().getASTType(),
+            getASTContext().getErrorDecl())
+        };
+
+        outerError = emitExistentialErasure(
+            loc,
+            innerErrorType.getASTType(),
+            getTypeLowering(innerErrorType),
+            getTypeLowering(outerErrorType),
+            getASTContext().AllocateCopy(conformances),
+            SGFContext(),
+            [&](SGFContext C) -> ManagedValue {
+              if (innerError->getType().isAddress()) {
+                return emitLoad(loc, innerError,
+                                getTypeLowering(innerErrorType), SGFContext(),
+                                IsTake);
+              }
+
+              return ManagedValue::forForwardedRValue(*this, innerError);
             }).forward(*this);
+      } else if (innerError->getType().isAddress()) {
+        // Load the inner error, if it was returned indirectly.
+        outerError = emitLoad(loc, innerError, getTypeLowering(innerErrorType),
+                              SGFContext(), IsTake).forward(*this);
+      } else {
+        outerError = innerError;
       }
 
+
       // If the outer error is returned indirectly, copy from the converted
       // inner error to the outer error slot.
       if (IndirectErrorResult) {

lib/Sema/TypeCheckEffects.cpp

@@ -718,6 +718,17 @@ class Classification {
     return result;
   }
 
+  /// Return a classification that promotes a typed throws effect to an
+  /// untyped throws effect.
+  Classification promoteToUntypedThrows() const {
+    if (!hasThrows())
+      return *this;
+
+    Classification result(*this);
+    result.ThrownError = ThrownError->getASTContext().getErrorExistentialType();
+    return result;
+  }
+
   /// Return a classification that only retains the parts of this
   /// classification for the requested effect kind.
   Classification onlyEffect(EffectKind kind) const {
@@ -1109,9 +1120,15 @@ class ApplyClassifier {
         }
 
         for (unsigned i = 0, e = params.size(); i < e; ++i) {
-          result.merge(classifyArgument(args->getExpr(i),
-                                        params[i].getParameterType(),
-                                        kind));
+          auto argClassification = classifyArgument(
+              args->getExpr(i), params[i].getParameterType(), kind);
+
+          // Rethrows is untyped, so
+          if (kind == EffectKind::Throws) {
+            argClassification = argClassification.promoteToUntypedThrows();
+          }
+
+          result.merge(argClassification);
         }
 
         return;

test/Profiler/coverage_closure_returns_never.swift

@@ -6,8 +6,7 @@
 // CHECK-NOT:  increment_profiler_counter
 // CHECK:      [[LOAD:%.*]] = load {{.*}} : $*Never
 // CHECK-NEXT: debug_value [[LOAD]] : $Never
-// CHECK-NEXT: debug_value undef : $any Error, var, name "$error", argno
-// CHECK-NEXT: unreachable
+// CHECK: unreachable
 
 func closure_with_fatal_error(_ arr: [Never]) {
 // CHECK-LABEL: sil_coverage_map {{.*}}// closure #1 (Swift.Never) -> Swift.Never

test/decl/func/typed_throws.swift

@@ -146,3 +146,11 @@ extension Either: Error where First: Error, Second: Error { }
 func f<E1, E2>(_ error: Either<E1, E2>) throws(Either<E1, E2>) {
   throw error
 }
+
+// Ensure that calls to 'rethrows' functions are always treated as throwing `any
+// Error`.
+func rethrowingFunc(body: () throws -> Void) rethrows { }
+
+func typedCallsRethrowingFunc<E>(body: () throws(E) -> Void) throws(E) {
+  try rethrowingFunc(body: body) // expected-error{{thrown expression type 'any Error' cannot be converted to error type 'E'}}
+}