SIL: Fix printing of opaque parameter types

While printing them as `some P` makes sense in the AST since they
only ever appear at their definition point, in the body of a SIL
function, opaque parameter types can be referenced by various
instructions, like any other generic parameter type.

Instead of printing out `some P` or `<anonymous>` depending on
context, neither of which actually parsed, instead print them
with the canonical type `τ_d_i` notation. Since it's printed this
way in the generic parameter list as well, it parses back in.

Fixes rdar://problem/119823811.

Author: slavapestov

lib/AST/ASTPrinter.cpp

@@ -7756,10 +7756,20 @@ class TypePrinter : public TypeVisitor<TypePrinter> {
       // canonical types to sugared types.
       if (Options.GenericSig)
         T = Options.GenericSig->getSugaredType(T);
+
+      decl = T->getDecl();
     }
 
     // Print opaque types as "some ..."
     if (decl && decl->isOpaqueType()) {
+      // For SIL, we print opaque parameter types as canonical types, and parse
+      // them that way too (because they're printed in this way in the SIL
+      // generic parameter list).
+      if (Options.PrintInSILBody) {
+        Printer.printName(cast<GenericTypeParamType>(T->getCanonicalType())->getName());
+        return;
+      }
+
       // If we have and should print based on the type representation, do so.
       if (auto opaqueRepr = decl->getOpaqueTypeRepr()) {
         if (willUseTypeReprPrinting(opaqueRepr, Type(), Options)) {

lib/SIL/IR/SILPrinter.cpp

@@ -526,6 +526,12 @@ static void printSILFunctionNameAndType(
     for (auto *paramTy : genSig.getGenericParams()) {
       // Get a uniqued sugared name for the generic parameter type.
       auto sugaredTy = genEnv->getGenericSignature()->getSugaredType(paramTy);
+
+      // Opaque parameter types are printed as their canonical types and not
+      // the unparseable "<anonymous>".
+      if (sugaredTy->getDecl() && sugaredTy->getDecl()->isOpaqueType())
+        continue;
+
       Identifier name = sugaredTy->getName();
       while (!usedNames.insert(name).second) {
         disambiguatedNameBuf.clear();

test/SIL/Parser/opaque_parameter_roundtrip.swift

@@ -0,0 +1,20 @@
+
+// RUN: %target-swift-frontend -emit-silgen %s | %target-sil-opt | %FileCheck %s
+
+protocol P {}
+
+func bar(_: some P) {}
+
+func foo(_ x: some P) {
+  bar(x)
+}
+
+// CHECK-LABEL: sil hidden [ossa] @$s26opaque_parameter_roundtrip3fooyyxAA1PRzlF : $@convention(thin) <τ_0_0 where τ_0_0 : P> (@in_guaranteed τ_0_0) -> () {
+// CHECK: bb0(%0 : $*τ_0_0):
+// CHECK-NEXT: debug_value %0 : $*τ_0_0, let, name "x", argno 1, expr op_deref
+// CHECK-NEXT: // function_ref bar<A>(_:)
+// CHECK-NEXT: [[FN:%.*]] = function_ref @$s26opaque_parameter_roundtrip3baryyxAA1PRzlF : $@convention(thin) <τ_0_0 where τ_0_0 : P> (@in_guaranteed τ_0_0) -> ()
+// CHECK-NEXT: apply [[FN]]<τ_0_0>(%0) : $@convention(thin) <τ_0_0 where τ_0_0 : P> (@in_guaranteed τ_0_0) -> ()
+// CHECK-NEXT: [[RESULT:%.*]] = tuple ()
+// CHECK-NEXT: return [[RESULT]] : $()
+// CHECK-NEXT: } // end sil function '$s26opaque_parameter_roundtrip3fooyyxAA1PRzlF'

test/SILGen/objc_async.swift

@@ -303,9 +303,9 @@ extension OptionalMemberLookups {
 }
 
 
-// CHECK-LABEL: sil {{.*}} @$s10objc_async12checkHotdogsySSSgx_So8NSObjectCtYaKSo16HotdogCompetitorRzlF
+// CHECK-LABEL: sil {{.*}} @$s10objc_async12checkHotdogsySSSgx_So8NSObjectCtYaKSo16HotdogCompetitorRzlF : $@convention(thin) @async <τ_0_0 where τ_0_0 : HotdogCompetitor> (@guaranteed τ_0_0, @guaranteed NSObject) -> (@owned Optional<String>, @error any Error) {
 // CHECK: hop_to_executor {{.*}} : $MainActor
-// CHECK: [[AUTO_REL_STR:%.*]] = apply {{.*}}<some HotdogCompetitor>({{.*}}) : $@convention(objc_method)
+// CHECK: [[AUTO_REL_STR:%.*]] = apply {{.*}}<τ_0_0>({{.*}}) : $@convention(objc_method)
 // CHECK: [[UNMANAGED_OPTIONAL:%.*]] = load [trivial] {{.*}} : $*@sil_unmanaged Optional<NSError>
 // CHECK: [[MANAGED_OPTIONAL:%.*]] = unmanaged_to_ref [[UNMANAGED_OPTIONAL]] : $@sil_unmanaged Optional<NSError> to $Optional<NSError>
 // CHECK: [[RETAINED_OPTIONAL:%.*]] = copy_value [[MANAGED_OPTIONAL]] : $Optional<NSError>