better trait bound format

Author: Austaras

.github/workflows/CI.yml

@@ -15,7 +15,7 @@ jobs:
       - name: Setup .NET Core SDK
         uses: actions/setup-dotnet@v4
         with:
-          dotnet-version: '9.x.x'
+          dotnet-version: "9.x.x"
 
       - name: Install dependencies
         run: dotnet restore

README.MD

@@ -25,7 +25,7 @@ Test out various compiler technology with a toy compiler for a toy language **in
    - HM type inference with trait and operator overloading
    - c style function declaration that are hoisted and cannot capture environment
    - internal mutable
-   - impl block and trait, but user need to import them
+   - impl block and trait, but impl trait has name and user need to import them like in Scala
    - string is UTF8 and char is UTF32
 3. Pratically functional
    - provide immutable std lib and tail call optimization
@@ -60,6 +60,7 @@ Test out various compiler technology with a toy compiler for a toy language **in
   - [ ] field selection
   - [ ] existential type
   - [ ] TRIE based resolution
+  - [ ] name instance
   - [ ] lower
 - [ ] pattern match
   - [ ] coverage

src/Semantic/Library.fs

@@ -279,26 +279,38 @@ type Scheme =
             if this.Pred.Length = 0 then
                 res
             else
-                let print { Type = ty; Trait = tr } =
-                    let bound = ty[0].Print() + ": " + tr.Name.Sym
-
-                    if ty.Length = 1 then
-                        bound
-                    else
-                        let print (idx, ty: Type) =
-                            let ty = ty.Print()
-                            let idx = idx + 1
-
-                            if idx >= tr.FreeVarLength then
-                                let name = tr.DepName[idx - tr.FreeVarLength].Sym
-                                $"{name} = {ty}"
-                            else
-                                ty
-
-                        let gen = ty[1..] |> Array.indexed |> Array.map print |> String.concat ", "
-                        $"{bound}<{gen}>"
-
-                let pred = this.Pred |> Array.map print |> String.concat ", "
+                let print (ty: Type, pred: Pred[]) =
+                    let head = ty.Print() + ": "
+
+                    let print (tr: Trait) (idx: int, ty: Type) =
+                        let idx = idx + 1
+
+                        if idx >= tr.FreeVarLength then
+                            let name = tr.DepName[idx - tr.FreeVarLength].Sym
+                            $"{name} = {ty.Print()}"
+                        else
+                            ty.Print()
+
+                    let print (pred: Pred) =
+                        let tr = pred.Trait.Name.Sym
+
+                        if pred.Type.Length > 1 then
+                            let gen =
+                                pred.Type[1..]
+                                |> Array.indexed
+                                |> Array.map (print pred.Trait)
+                                |> String.concat ", "
+
+                            $"{tr}<{gen}>"
+                        else
+                            tr
+
+                    let bound = pred |> Array.map print |> String.concat " + "
+
+                    head + bound
+
+                let pred =
+                    this.Pred |> Array.groupBy _.Type[0] |> Array.map print |> String.concat ", "
 
                 $"{res} where {pred}"
 

test/Semantic/Type/Trait.fs

@@ -186,7 +186,7 @@ fn twice(c, a, b) {
     c.insert(a)
     c.insert(b)
 }"
-    |> toBe (Map [| "twice", "<T0, T1, T2>|T0, T1, T2| -> () where T0: Collect<T1>, T0: Collect<T2>" |])
+    |> toBe (Map [| "twice", "<T0, T1, T2>|T0, T1, T2| -> () where T0: Collect<T1> + Collect<T2>" |])
 
 [<Fact>]
 let GoodCollect () =