Simplify printfn usage when applied a constant string in Fable 3

[Zaid-Ajaj]

Description

Simplify printfn usage when applied a constant string to plain console.log when there is no custom formatting work to be done:

printfn "Hello"

compiles to

String_toConsole(String_printf("Hello"));

Instead compile to just

console.log("Hello")

by detecting the constant string usage in the AST.

Let me give this one a try too :)

• Fable version: 3.0.0-nagareyama-alpha-015
• Operating system: Windows 10

[alfonsogarciacaro]

Ok, please feel free to give it a go. Hopefully Fable is easier to contribute now :) Just a note of caution though, dealing with the print formatters is quite complicated because the F# compiler creates many closures around them and it's quite difficult to identify the AST for them. I've trying to simplify/optimize print formatters since the very first version of Fable, but at the end I opted for simplicity. We're also trying to remove complicated patterns in the FSharp2Fable step because accessing FCS BasicPatterns can be slow sometimes.