Allow decimal constants

[esbenbjerre]

The intention of this PR is to add support for the use of the literal attribute on decimals.

[<Literal>]letd=2.5m

• Allow decimal constant in PostInferenceChecks
• Add decimal arithmetic in TypedTreeOps
• Add DecimalConstantAttribute to TcGlobals
• Add codegen (initonly field with attribute + cctor) to IlxGen
• Fix broken tests
• Add test for pattern matching a value against a decimal literal
• Add test for incomplete pattern matching a value against a decimal literal
• Add test for usage and evaluation of decimal literal in quotations
• Add test C# interop

Related fsharp/fslang-suggestions#847

[github-actions]

❗ Release notes required

---

✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/9.0.200.md

[esbenbjerre]

@dotnet-policy-service agree

[T-Gro]

Hi @esbenbjerre , thanks for this contribution.
Here are a few test areas I would expect to be covered as part of this PR:

• Pattern matching a value against a decimal literal (IL test, compileAndRun test)
• Incomplete Pattern matching with decimal literals
• Usage and evaluation of decimal literal in quotations (compileAndRun test)
• Consumption of the literal in C# (multiproject test for interop), tooling support from C# (referencing a .dll with the decimal constant in a C# project from IDE)

[esbenbjerre]

Thanks @T-Gro. I'm still trying to codegen the cctor code. Would you prefer I convert it to draft until it's ready?

[vzarytovskii]

Yeah, let's convert it to draft so it doesn't pop up on our triage radar

[esbenbjerre]

@T-Gro I have a couple of questions regarding the test requirements.

• What is expected in terms of IL for pattern matching?
• For C# interop is it a manual test or automated? And if automated is there anything similar in the repo I could use for inspiration?

[T-Gro]

@T-Gro I have a couple of questions regarding the test requirements.

• What is expected in terms of IL for pattern matching?
• For C# interop is it a manual test or automated? And if automated is there anything similar in the repo I could use for inspiration?

For the C# interop, the test framework in "ComponentTests" suite can handle CsharpSource as well.
See e.g. here:

fsharp/tests/FSharp.Compiler.ComponentTests/Interop/SimpleInteropTests.fs

Line 44 in 86b7584

letapp=

(or if curious, just look at more usages of the "CSharp" function.

For pattern matching a decimal literal, the IL should contain:

• Init code for the decimal value
• Loading up of the decimal
• Calling .Equals() on it against the value being pattern matched.

For inspiration, look at tests which use the "verifyIL" function in the "ComponentTests" suite. I start such tests by writing a minimal F# sample, let the verification fail, and then copy relevant snippets of IL from the test output into the assertion list (that is assuming the IL looks good)

[esbenbjerre]

@T-Gro I'm getting Invalid assembly name: Name contains invalid characters. when trying to use the CSharp function.
I'm getting it with or without the literal attribute. The code should be valid and does compile in a mixed C#/F# project (sans literal attribute). The same error happens if I change x to an int.

namespaceInteropopenXunitopenFSharp.Test.Compilermodule``TestDeleteMe`` =[<Fact>]let``Instantiate F# decimal literal from C#`` ()=letFSLib=
FSharp """namespace Interop.FSmodule DecimalLiteral = [<Literal>] let x = 7m"""|> withName "FSLib"letapp=
CSharp """using System;using Interop.FS;public class C { public Decimal y = DecimalLiteral.x;}"""|> withReferences [FSLib]
app
|> compile
|> shouldSucceed

results in

[xUnit.net 00:00:03.02] Interop.TestDeleteMe.Instantiate F# decimal literal from C# [FAIL]
Failed Interop.TestDeleteMe.Instantiate F# decimal literal from C# [2 s]
Error Message:
System.Exception : Operation failed (expected to succeed).
All errors:
[{ Error = Error 8203
Range = { StartLine = 0
StartColumn = 0
EndLine = 0
EndColumn = 0 }
NativeRange = (0,0--0,0)
Message = "Invalid assembly name: Name contains invalid characters."
SubCategory = "" }]
Stack Trace:
at FSharp.Test.Compiler.Assertions.shouldSucceed(CompilationResult result) in /Users/ebj/Source/fsharp/tests/FSharp.Test.Utilities/Compiler.fs:line 1529
at Interop.TestDeleteMe.Instantiate F# decimal literal from C#() in /Users/ebj/Source/fsharp/tests/FSharp.Compiler.ComponentTests/Interop/TestDeleteMe.fs:line 29
at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)

[esbenbjerre]

I managed to solve it by adding |> withName "CSharpApp" to the CSharpCompilationUnit.

[edgarfgp]

I think this is worth a small RFC so we can track this later in the language spec.

[vzarytovskii]

Yes, this will need an rfc

[esbenbjerre]

Created RFC PR here fsharp/fslang-design#790