fix: IndexSignature decorated with readonly should not generate a setter

[converter]

=== changelog ===
```ts
export interface MyType {
    readonly [n: number]: string;
}
```

```fs
[<AllowNullLiteral>]
[<Interface>]
type MyType =
    [<EmitIndexer>]
    abstract member Item: n: float -> string with get
```
=== changelog ===

Fix #136

Author: MangelMaxime

src/Glutinum.Converter/GlueAST.fs

@@ -101,6 +101,7 @@ type GlueIndexSignature =
     {
         Parameters: GlueParameter list
         Type: GlueType
+        IsReadOnly: bool
     }
 
 type GlueMethodSignature =

src/Glutinum.Converter/Reader/Declaration.fs

@@ -66,6 +66,14 @@ let readDeclaration
         ({
             Parameters = reader.ReadParameters indexSignature.parameters
             Type = reader.ReadTypeNode(Some indexSignature.``type``)
+            IsReadOnly =
+                match indexSignature.modifiers with
+                | Some modifiers ->
+                    modifiers
+                    |> Seq.exists (fun modifier ->
+                        modifier?kind = Ts.SyntaxKind.ReadonlyKeyword
+                    )
+                | None -> false
         }
         : GlueIndexSignature)
         |> GlueMember.IndexSignature

src/Glutinum.Converter/Transform.fs

@@ -1157,7 +1157,11 @@ module private TransformMembers =
                     TypeParameters = []
                     IsOptional = false
                     IsStatic = false
-                    Accessor = Some FSharpAccessor.ReadWrite
+                    Accessor =
+                        if indexSignature.IsReadOnly then
+                            Some FSharpAccessor.ReadOnly
+                        else
+                            Some FSharpAccessor.ReadWrite
                     Accessibility = FSharpAccessibility.Public
                     XmlDoc = []
                     Body = FSharpMemberInfoBody.NativeOnly

src/Glutinum.Web/Pages/Editors.GlueAST.GlueASTViewer.fs

@@ -24,6 +24,9 @@ type GlueASTViewer =
     static member private IsOptional(isOptional: bool) =
         ASTViewer.renderKeyValue "IsOptional" (string isOptional)
 
+    static member private IsReadOnly(isReadOnly: bool) =
+        ASTViewer.renderKeyValue "IsReadOnly" (string isReadOnly)
+
     static member private IsStatic(isStatic: bool) =
         ASTViewer.renderKeyValue "IsStatic" (string isStatic)
 
@@ -165,6 +168,7 @@ type GlueASTViewer =
             ASTViewer.renderNode "IndexSignature" [
                 GlueASTViewer.Parameters indexSignature.Parameters
                 GlueASTViewer.Type indexSignature.Type
+                GlueASTViewer.IsReadOnly indexSignature.IsReadOnly
             ]
 
         | GlueMember.Property propertyInfo ->

tests/specs/references/typeLiteral/indexSignature/readonly.d.ts

@@ -0,0 +1,3 @@
+export interface MyType {
+    readonly [n: number]: string;
+}

tests/specs/references/typeLiteral/indexSignature/readonly.fsx

@@ -0,0 +1,15 @@
+module rec Glutinum
+
+open Fable.Core
+open Fable.Core.JsInterop
+open System
+
+[<AllowNullLiteral>]
+[<Interface>]
+type MyType =
+    [<EmitIndexer>]
+    abstract member Item: n: float -> string with get
+
+(***)
+#r "nuget: Fable.Core"
+(***)