NCGenerics: remove the reverse-condfail workaround

This should no longer be needed, after having staged the first set of
changes in, as it was a temporary workaround.

resolves rdar://131560183

Author: kavon

docs/Generics/chapters/class-inheritance.tex

@@ -452,7 +452,7 @@
 \item The witness must be in a protocol extension. If the witness is a method on the class, there is no way to observe the concrete substitution for the protocol \texttt{Self} type, because it is not a generic parameter of the class method.
 \item (The hack) The interface type of the protocol requirement must not mention any associated types.
 \end{enumerate}
-The determination of whether to use a static or covariant \texttt{Self} type for a class conformance is implemented by the type cheker function \texttt{matchWitness()}.
+The determination of whether to use a static or covariant \texttt{Self} type for a class conformance is implemented by the type checker function \texttt{matchWitness()}.
 
 Indeed, Condition~3 is a hack; it opens up an exception where the soundness hole we worked so hard to close is once again allowed. In an ideal world, Conditions 1~and~2 would be sufficient, but by the time the soundness hole was discovered and closed, existing code had already been written taking advantage of it. The scenario necessitating Condition~3 is when the default implementation appears in a \emph{constrained} protocol extension:
 \begin{Verbatim}

include/swift/Basic/Features.def

@@ -395,8 +395,6 @@ EXPERIMENTAL_FEATURE(DebugDescriptionMacro, true)
 
 EXPERIMENTAL_FEATURE(ReinitializeConsumeInMultiBlockDefer, false)
 
-EXPERIMENTAL_FEATURE(SE427NoInferenceOnExtension, false)
-
 #undef EXPERIMENTAL_FEATURE_EXCLUDED_FROM_MODULE_INTERFACE
 #undef EXPERIMENTAL_FEATURE
 #undef UPCOMING_FEATURE

lib/AST/FeatureSet.cpp

@@ -765,7 +765,6 @@ static bool usesFeatureSensitive(Decl *decl) {
 
 UNINTERESTING_FEATURE(DebugDescriptionMacro)
 UNINTERESTING_FEATURE(ReinitializeConsumeInMultiBlockDefer)
-UNINTERESTING_FEATURE(SE427NoInferenceOnExtension)
 
 // ----------------------------------------------------------------------------
 // MARK: - FeatureSet

lib/Sema/TypeCheckGeneric.cpp

@@ -788,15 +788,6 @@ GenericSignatureRequest::evaluate(Evaluator &evaluator,
     // to invertible protocols. This forces people to write out the conditions.
     inferInvertibleReqs = !ext->isAddingConformanceToInvertible();
 
-    // FIXME: to workaround a reverse condfail, always infer the requirements if
-    //  the extension is in a swiftinterface file. This is temporary and should
-    //  be removed soon. (rdar://130424971)
-    if (auto *sf = ext->getOutermostParentSourceFile()) {
-      if (sf->Kind == SourceFileKind::Interface
-          && !ctx.LangOpts.hasFeature(Feature::SE427NoInferenceOnExtension))
-        inferInvertibleReqs = true;
-    }
-
     collectAdditionalExtensionRequirements(ext->getExtendedType(), extraReqs);
 
     auto *extendedNominal = ext->getExtendedNominal();

test/ModuleInterface/noncopyable_generics.swift

@@ -1,20 +1,15 @@
 // RUN: %empty-directory(%t)
 
-// Due to SE427NoInferenceOnExtension not being in production
-// REQUIRES: asserts
-
 // RUN: %target-swift-frontend -swift-version 5 -enable-library-evolution -emit-module \
 // RUN:     -enable-experimental-feature SuppressedAssociatedTypes \
 // RUN:     -enable-experimental-feature NonescapableTypes \
-// RUN:     -enable-experimental-feature SE427NoInferenceOnExtension \
 // RUN:     -o %t/NoncopyableGenerics_Misc.swiftmodule \
 // RUN:     -emit-module-interface-path %t/NoncopyableGenerics_Misc.swiftinterface \
 // RUN:     %S/Inputs/NoncopyableGenerics_Misc.swift
 
 // RUN: %target-swift-frontend -swift-version 5 -enable-library-evolution -emit-module \
 // RUN:     -enable-experimental-feature SuppressedAssociatedTypes \
 // RUN:     -enable-experimental-feature NonescapableTypes \
-// RUN:     -enable-experimental-feature SE427NoInferenceOnExtension \
 // RUN:     -o %t/Swiftskell.swiftmodule \
 // RUN:     -emit-module-interface-path %t/Swiftskell.swiftinterface \
 // RUN:     %S/../Inputs/Swiftskell.swift
@@ -29,19 +24,16 @@
 // RUN: %target-swift-frontend -compile-module-from-interface \
 // RUN:     -enable-experimental-feature SuppressedAssociatedTypes \
 // RUN:     -enable-experimental-feature NonescapableTypes \
-// RUN:     -enable-experimental-feature SE427NoInferenceOnExtension \
 // RUN:    %t/NoncopyableGenerics_Misc.swiftinterface -o %t/NoncopyableGenerics_Misc.swiftmodule
 
 // RUN: %target-swift-frontend -compile-module-from-interface \
 // RUN:     -enable-experimental-feature SuppressedAssociatedTypes \
 // RUN:     -enable-experimental-feature NonescapableTypes \
-// RUN:     -enable-experimental-feature SE427NoInferenceOnExtension \
 // RUN:    %t/Swiftskell.swiftinterface -o %t/Swiftskell.swiftmodule
 
 // RUN: %target-swift-frontend -emit-silgen -I %t %s \
 // RUN:     -enable-experimental-feature SuppressedAssociatedTypes \
 // RUN:    -enable-experimental-feature NonescapableTypes \
-// RUN:     -enable-experimental-feature SE427NoInferenceOnExtension \
 // RUN:    -o %t/final.silgen
 
 // RUN: %FileCheck %s --check-prefix=CHECK-SILGEN < %t/final.silgen