[clang][NFC] Add missing placement-new after Allocate() calls (llvm#68382)

While working on llvm#68377 inspecting `Allocate()` calls, I found out that
there are couple of places where we forget to use placement-new to
create objects in the allocated memory.

Author: Endilll

clang/lib/AST/DeclCXX.cpp

@@ -1484,7 +1484,8 @@ void CXXRecordDecl::setCaptures(ASTContext &Context,
     if (Captures[I].isExplicit())
       ++Data.NumExplicitCaptures;
 
-    *ToCapture++ = Captures[I];
+    new (ToCapture) LambdaCapture(Captures[I]);
+    ToCapture++;
   }
 
   if (!lambdaIsDefaultConstructibleAndAssignable())

clang/lib/AST/DeclObjC.cpp

@@ -931,8 +931,8 @@ void ObjCMethodDecl::setParamsAndSelLocs(ASTContext &C,
   unsigned Size = sizeof(ParmVarDecl *) * NumParams +
                   sizeof(SourceLocation) * SelLocs.size();
   ParamsAndSelLocs = C.Allocate(Size);
-  std::copy(Params.begin(), Params.end(), getParams());
-  std::copy(SelLocs.begin(), SelLocs.end(), getStoredSelLocs());
+  std::uninitialized_copy(Params.begin(), Params.end(), getParams());
+  std::uninitialized_copy(SelLocs.begin(), SelLocs.end(), getStoredSelLocs());
 }
 
 void ObjCMethodDecl::getSelectorLocs(

clang/lib/Serialization/ASTReaderDecl.cpp

@@ -2002,13 +2002,16 @@ void ASTDeclReader::ReadCXXDefinitionData(
       case LCK_StarThis:
       case LCK_This:
       case LCK_VLAType:
-        *ToCapture++ = Capture(Loc, IsImplicit, Kind, nullptr,SourceLocation());
+        new (ToCapture)
+            Capture(Loc, IsImplicit, Kind, nullptr, SourceLocation());
+        ToCapture++;
         break;
       case LCK_ByCopy:
       case LCK_ByRef:
         auto *Var = readDeclAs<VarDecl>();
         SourceLocation EllipsisLoc = readSourceLocation();
-        *ToCapture++ = Capture(Loc, IsImplicit, Kind, Var, EllipsisLoc);
+        new (ToCapture) Capture(Loc, IsImplicit, Kind, Var, EllipsisLoc);
+        ToCapture++;
         break;
       }
     }