Fix property wrapper crasher

Due to insufficiently robust argument emission code, certain combinations of language features could cause a call to a property wrapper backing initalizer to have mismatched argument types, causing an assertion failure in SILGenApply. This commit moves SILGenFunction::emitApplyOfPropertyWrapperBackingInitializer() into SILGenApply so it can use CallEmission and PreparedArguments to emit the call with full generality. Fixes rdar://problem/55995892.

Author: beccadax

lib/SILGen/SILGenApply.cpp

@@ -5006,6 +5006,44 @@ RValue SILGenFunction::emitApplyMethod(SILLocation loc, ConcreteDeclRef declRef,
   return emission.apply(C);
 }
 
+RValue SILGenFunction::emitApplyOfPropertyWrapperBackingInitializer(
+    SILLocation loc,
+    VarDecl *var,
+    RValue &&originalValue,
+    SGFContext C) {
+  SILDeclRef constant(var, SILDeclRef::Kind::PropertyWrapperBackingInitializer);
+
+  SubstitutionMap subs;
+  auto varDC = var->getInnermostDeclContext();
+  if (auto genericSig = varDC->getGenericSignatureOfContext()) {
+    subs = SubstitutionMap::get(
+        genericSig,
+        [&](SubstitutableType *type) {
+          if (auto gp = type->getAs<GenericTypeParamType>()) {
+            return F.mapTypeIntoContext(gp);
+          }
+
+          return Type(type);
+        },
+        LookUpConformanceInModule(varDC->getParentModule()));
+  }
+
+  FormalEvaluationScope writebackScope(*this);
+
+  auto callee = Callee::forDirect(*this, constant, subs, loc);
+  auto substFnType = callee.getSubstFormalType();
+
+  CallEmission emission(*this, std::move(callee), std::move(writebackScope));
+
+  PreparedArguments args(substFnType->getAs<AnyFunctionType>()->getParams());
+  args.add(loc, std::move(originalValue));
+  emission.addCallSite(loc, std::move(args),
+                       substFnType->getResult()->getCanonicalType(),
+                       /*throws=*/false);
+  
+  return emission.apply(C);
+}
+
 /// Emit a literal that applies the various initializers.
 RValue SILGenFunction::emitLiteral(LiteralExpr *literal, SGFContext C) {
   ConcreteDeclRef builtinInit;

lib/SILGen/SILGenExpr.cpp

@@ -2235,46 +2235,6 @@ RValue SILGenFunction::emitApplyOfStoredPropertyInitializer(
                    subs, {}, calleeTypeInfo, ApplyOptions::None, C);
 }
 
-RValue SILGenFunction::emitApplyOfPropertyWrapperBackingInitializer(
-    SILLocation loc,
-    VarDecl *var,
-    RValue &&originalValue,
-    SGFContext C) {
-  SILDeclRef constant(var, SILDeclRef::Kind::PropertyWrapperBackingInitializer);
-  auto fnRef = ManagedValue::forUnmanaged(emitGlobalFunctionRef(loc, constant));
-  auto fnType = fnRef.getType().castTo<SILFunctionType>();
-
-  SubstitutionMap subs;
-  auto varDC = var->getInnermostDeclContext();
-  if (auto genericSig = varDC->getGenericSignatureOfContext()) {
-    subs = SubstitutionMap::get(
-        genericSig,
-        [&](SubstitutableType *type) {
-          if (auto gp = type->getAs<GenericTypeParamType>()) {
-            return F.mapTypeIntoContext(gp);
-          }
-
-          return Type(type);
-        },
-        LookUpConformanceInModule(varDC->getParentModule()));
-  }
-
-  auto substFnType = fnType->substGenericArgs(SGM.M, subs);
-
-  CanType resultType =
-      F.mapTypeIntoContext(var->getPropertyWrapperBackingPropertyType())
-        ->getCanonicalType();
-  AbstractionPattern origResultType(resultType);
-  CalleeTypeInfo calleeTypeInfo(substFnType, origResultType, resultType);
-  ResultPlanPtr resultPlan =
-      ResultPlanBuilder::computeResultPlan(*this, calleeTypeInfo, loc, C);
-  ArgumentScope argScope(*this, loc);
-  SmallVector<ManagedValue, 2> args;
-  std::move(originalValue).getAll(args);
-  return emitApply(std::move(resultPlan), std::move(argScope), loc, fnRef, subs,
-                   args, calleeTypeInfo, ApplyOptions::None, C);
-}
-
 RValue RValueEmitter::visitDestructureTupleExpr(DestructureTupleExpr *E,
                                                 SGFContext C) {
   // Emit the sub-expression tuple and destructure it into elements.

test/SILGen/property_wrappers_library_evolution.swift

@@ -0,0 +1,10 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -emit-module -o %t -enable-library-evolution %S/Inputs/property_wrapper_defs.swift
+// RUN: %target-swift-emit-silgen -primary-file %s -I %t -enable-library-evolution
+import property_wrapper_defs
+
+// rdar://problem/55995892
+// This is a crash that occurs only with -enable-library-evolution.
+
+public enum E { case a }
+struct M { @MyPublished private var e = E.a }