Minor TypeChecker optimization (#2900)
Minor TypeChecker optimization (#2900)


syeerzy/visualfsharp,brettfo/visualfsharp,syeerzy/visualfsharp,dsyme/FSharp.Compiler.Service,ncave/FSharp.Compiler.Service,fsharp/fsharp,dsyme/fsharp,sergey-tihon/FSharp.Compiler.Service,syeerzy/visualfsharp,ncave/FSharp.Compiler.Service,dsyme/fsharp,Jand42/FSharp.Compiler.Service,syeerzy/visualfsharp,fsharp/fsharp,dsyme/fsharp,Jand42/FSharp.Compiler.Service,dsyme/fsharp,syeerzy/visualfsharp,brettfo/visualfsharp,cloudRoutine/FSharp.Compiler.Service,brettfo/visualfsharp,Jand42/FSharp.Compiler.Service,sergey-tihon/FSharp.Compiler.Service,cloudRoutine/FSharp.Compiler.Service,dsyme/FSharp.Compiler.Service,brettfo/visualfsharp,sergey-tihon/FSharp.Compiler.Service,cloudRoutine/FSharp.Compiler.Service,ncave/FSharp.Compiler.Service,dsyme/fsharp,dsyme/fsharp,fsharp/fsharp,brettfo/visualfsharp,brettfo/visualfsharp,dsyme/FSharp.Compiler.Service,syeerzy/visualfsharp,dsyme/fsharp