[Type checker] Delete unnecessary, bogus optimization for initializers.

include/swift/AST/Decl.h

@@ -445,17 +445,10 @@ class alignas(1 << DeclAlignInBits) Decl {
     /// to this declaration.
     unsigned AddedImplicitInitializers : 1;
 
-    /// \brief Whether or not this declaration has a failable initializer member,
-    /// and whether or not we've actually searched for one.
-    unsigned HasFailableInits : 1;
-
-    /// Whether we have already searched for failable initializers.
-    unsigned SearchedForFailableInits : 1;
-
     /// Whether there is are lazily-loaded conformances for this nominal type.
     unsigned HasLazyConformances : 1;
   };
-  enum { NumNominalTypeDeclBits = NumGenericTypeDeclBits + 5 };
+  enum { NumNominalTypeDeclBits = NumGenericTypeDeclBits + 3 };
   static_assert(NumNominalTypeDeclBits <= 32, "fits in an unsigned");
 
   class ProtocolDeclBitfields {
@@ -2744,8 +2737,6 @@ class NominalTypeDecl : public GenericTypeDecl, public IterableDeclContext {
     NominalTypeDeclBits.HasDelayedMembers = false;
     NominalTypeDeclBits.AddedImplicitInitializers = false;
     ExtensionGeneration = 0;
-    NominalTypeDeclBits.SearchedForFailableInits = false;
-    NominalTypeDeclBits.HasFailableInits = false;
     NominalTypeDeclBits.HasLazyConformances = false;
   }
 
@@ -2795,19 +2786,6 @@ class NominalTypeDecl : public GenericTypeDecl, public IterableDeclContext {
     NominalTypeDeclBits.AddedImplicitInitializers = true;
   }
 
-  bool getHasFailableInits() const {
-    return NominalTypeDeclBits.HasFailableInits;
-  }
-  void setHasFailableInits(bool failable = true) {
-    NominalTypeDeclBits.HasFailableInits = failable;
-  }
-  void setSearchedForFailableInits(bool searched = true) {
-    NominalTypeDeclBits.SearchedForFailableInits = searched;
-  }
-  bool getSearchedForFailableInits() const {
-    return NominalTypeDeclBits.SearchedForFailableInits;
-  }
-
   /// Compute the type of this nominal type.
   void computeType();
 

lib/Sema/CSGen.cpp

@@ -678,56 +678,6 @@ namespace {
     }
   }
 
-  /// Determine whether or not a given NominalTypeDecl has a failable
-  /// initializer member.
-  bool hasFailableInits(NominalTypeDecl *NTD,
-                        ConstraintSystem *CS) {
-
-    // TODO: Note that we search manually, rather than invoking lookupMember
-    // on the ConstraintSystem object. Because this is a hot path, this keeps
-    // the overhead of the check low, and is twice as fast.
-    if (!NTD->getSearchedForFailableInits()) {
-      // Set flag before recursing to catch circularity.
-      NTD->setSearchedForFailableInits();
-
-      for (auto member : NTD->getMembers()) {
-        if (auto CD = dyn_cast<ConstructorDecl>(member)) {
-          if (CD->getFailability()) {
-            NTD->setHasFailableInits();
-            break;
-          }
-        }
-      }
-
-      if (!NTD->getHasFailableInits()) {
-        for (auto extension : NTD->getExtensions()) {
-          for (auto member : extension->getMembers()) {
-            if (auto CD = dyn_cast<ConstructorDecl>(member)) {
-              if (CD->getFailability()) {
-                NTD->setHasFailableInits();
-                break;
-              }
-            }
-          }
-        }
-
-        if (!NTD->getHasFailableInits()) {
-          for (auto parentTyLoc : NTD->getInherited()) {
-            if (auto nominalType =
-                parentTyLoc.getType()->getAs<NominalType>()) {
-              if (hasFailableInits(nominalType->getDecl(), CS)) {
-                NTD->setHasFailableInits();
-                break;
-              }
-            }
-          }
-        }
-      }
-    }
-
-    return NTD->getHasFailableInits();
-  }
-
   size_t getOperandCount(Type t) {
     size_t nOperands = 0;
 
@@ -2385,25 +2335,6 @@ namespace {
         if (auto fnType = CS.getType(fnExpr)->getAs<AnyFunctionType>()) {
           outputTy = fnType->getResult();
         }
-      } else if (auto TE = dyn_cast<TypeExpr>(fnExpr)) {
-        outputTy = CS.getInstanceType(TE);
-        NominalTypeDecl *NTD = nullptr;
-
-        if (auto nominalType = outputTy->getAs<NominalType>()) {
-          NTD = nominalType->getDecl();
-        } else if (auto bgT = outputTy->getAs<BoundGenericType>()) {
-          NTD = bgT->getDecl();
-        }
-
-        if (NTD) {
-          if (!(isa<ClassDecl>(NTD) || isa<StructDecl>(NTD)) ||
-              hasFailableInits(NTD, &CS)) {
-            outputTy = Type();
-          }
-        } else {
-          outputTy = Type();
-        }
-
       } else if (auto OSR = dyn_cast<OverloadSetRefExpr>(fnExpr)) {
         if (auto FD = dyn_cast<FuncDecl>(OSR->getDecls()[0])) {
 

test/Constraints/construction.swift

@@ -139,3 +139,16 @@ Int(i32 - 2 + 1) // expected-warning{{unused}}
 let xx: UInt64 = 100
 let yy = ((xx + 10) - 5) / 5
 let zy = (xx + (10 - 5)) / 5
+
+// rdar://problem/30588177
+struct S3 {
+  init() { }
+}
+
+let s3a = S3()
+
+extension S3 {
+  init?(maybe: S3) { return nil }
+}
+
+let s3b = S3(maybe: s3a)