Make struct-declarations polymorphic

src/checker.ts

@@ -482,7 +482,7 @@ abstract class SchemeBase {
 class Forall extends SchemeBase {
 
   public constructor(
-    public tvs: TVar[],
+    public typeVars: TVar[],
     public constraints: Constraint[],
     public type: Type,
   ) {
@@ -599,7 +599,7 @@ export class Checker {
 
   private instantiate(scheme: Scheme, node: Syntax | null): Type {
     const sub = new TVSub();
-    for (const tv of scheme.tvs) {
+    for (const tv of scheme.typeVars) {
       sub.set(tv, this.createTypeVar());
     }
     for (const constraint of scheme.constraints) {
@@ -891,7 +891,7 @@ export class Checker {
 
   }
 
-  public inferTypeExpression(node: TypeExpression): Type {
+  public inferTypeExpression(node: TypeExpression, introduceTypeVars = false): Type {
 
     switch (node.kind) {
 
@@ -907,6 +907,22 @@ export class Checker {
         return type;
       }
 
+      case SyntaxKind.VarTypeExpression:
+      {
+        const scheme = this.lookup(node.name.text);
+        if (scheme === null) {
+          if (!introduceTypeVars) {
+            this.diagnostics.add(new BindingNotFoudDiagnostic(node.name.text, node.name));
+          }
+          const type = this.createTypeVar();
+          this.addBinding(node.name.text, new Forall([], [], type));
+          return type;
+        }
+        assert(scheme.typeVars.length === 0);
+        assert(scheme.constraints.length === 0);
+        return scheme.type;
+      }
+
       case SyntaxKind.ArrowTypeExpression:
       {
         const paramTypes = [];
@@ -1129,6 +1145,7 @@ export class Checker {
         break;
       }
 
+      case SyntaxKind.EnumDeclaration:
       case SyntaxKind.StructDeclaration:
         break;
 
@@ -1169,6 +1186,7 @@ export class Checker {
       case SyntaxKind.IfStatement:
       case SyntaxKind.ReturnStatement:
       case SyntaxKind.ExpressionStatement:
+      case SyntaxKind.EnumDeclaration:
       case SyntaxKind.StructDeclaration:
         break;
 
@@ -1208,16 +1226,36 @@ export class Checker {
       case SyntaxKind.ReturnStatement:
         break;
 
+      case SyntaxKind.EnumDeclaration:
+      {
+        // TODO complete this
+        break;
+      }
+
       case SyntaxKind.StructDeclaration:
       {
+        const env = node.typeEnv = new TypeEnv(parentEnv);
+        const typeVars = new TVSet();
+        const constraints = new ConstraintSet();
+        const context: InferContext = {
+          constraints,
+          typeVars,
+          env,
+          returnType: null,
+        };
+        this.pushContext(context);
+        for (const varExpr of node.typeVars) {
+          env.add(varExpr.text, new Forall([], [], this.createTypeVar()));
+        }
         const fields = new Map<string, Type>();
         if (node.members !== null) {
           for (const member of node.members) {
             fields.set(member.name.text, this.inferTypeExpression(member.typeExpr));
           }
         }
+        this.popContext(context);
         const type = new TRecord(node, fields);
-        parentEnv.add(node.name.text, new Forall([], [], type));
+        parentEnv.add(node.name.text, new Forall(typeVars, constraints, type));
         break;
       }
 

src/cst.ts

@@ -107,6 +107,7 @@ export const enum SyntaxKind {
   // Type expressions
   ReferenceTypeExpression,
   ArrowTypeExpression,
+  VarTypeExpression,
 
   // Patterns
   BindPattern,
@@ -240,6 +241,7 @@ export class Scope {
       case SyntaxKind.ReturnStatement:
       case SyntaxKind.IfStatement:
         break;
+      case SyntaxKind.EnumDeclaration:
       case SyntaxKind.StructDeclaration:
         break;
       case SyntaxKind.LetDeclaration:
@@ -411,6 +413,32 @@ abstract class SyntaxBase {
 
 }
 
+export function forEachChild(node: Syntax, callback: (node: Syntax) => void): void {
+
+  for (const key of Object.getOwnPropertyNames(node)) {
+    if (isIgnoredProperty(key)) {
+      continue;
+    }
+    visitField((node as any)[key]);
+  }
+
+  function visitField(field: any): void {
+    if (field === null) {
+      return;
+    }
+    if (Array.isArray(field)) {
+      for (const element of field) {
+        visitField(element);
+      }
+      return;
+    }
+    if (field instanceof SyntaxBase) {
+      callback(field as Syntax);
+    }
+  }
+  
+}
+
 abstract class TokenBase extends SyntaxBase {
 
   private endPos: TextPosition | null = null;
@@ -939,9 +967,30 @@ export class ReferenceTypeExpression extends SyntaxBase {
 
 }
 
+export class VarTypeExpression extends SyntaxBase {
+
+  public readonly kind = SyntaxKind.VarTypeExpression;
+
+  public constructor(
+    public name: Identifier
+  ) {
+    super();
+  }
+
+  public getFirstToken(): Token {
+    return this.name;
+  }
+
+  public getLastToken(): Token {
+    return this.name;
+  }
+
+}
+
 export type TypeExpression
   = ReferenceTypeExpression
   | ArrowTypeExpression
+  | VarTypeExpression
 
 export class BindPattern extends SyntaxBase {
 
@@ -1686,6 +1735,7 @@ export class StructDeclaration extends SyntaxBase {
     public pubKeyword: PubKeyword | null,
     public structKeyword: StructKeyword,
     public name: IdentifierAlt,
+    public typeVars: Identifier[],
     public members: StructDeclarationField[] | null,
   ) {
     super();

src/parser.ts

@@ -51,6 +51,7 @@ import {
   EnumDeclarationStructElement,
   EnumDeclaration,
   EnumDeclarationTupleElement,
+  VarTypeExpression,
 } from "./cst"
 import { Stream } from "./util";
 
@@ -168,6 +169,11 @@ export class Parser {
   public parsePrimitiveTypeExpression(): TypeExpression {
     const t0 = this.peekToken();
     switch (t0.kind) {
+      case SyntaxKind.Identifier:
+      {
+        this.getToken();
+        return new VarTypeExpression(t0);
+      }
       case SyntaxKind.IdentifierAlt:
         return this.parseReferenceTypeExpression();
       default:
@@ -288,6 +294,7 @@ export class Parser {
         for (;;) {
           const t2 = this.peekToken();
           if (t2.kind === SyntaxKind.LineFoldEnd
+            || t2.kind === SyntaxKind.Comma
             || t2.kind === SyntaxKind.RParen
             || t2.kind === SyntaxKind.RBrace
             || t2.kind === SyntaxKind.RBracket
@@ -481,10 +488,14 @@ export class Parser {
       this.raiseParseError(t0, [ SyntaxKind.StructKeyword ]);
     }
     const name = this.expectToken(SyntaxKind.IdentifierAlt);
-    const t2 = this.peekToken()
+    let t2 = this.getToken();
+    const typeVars = [];
+    while (t2.kind === SyntaxKind.Identifier) {
+      typeVars.push(t2);
+      t2 = this.getToken();
+    }
     let members = null;
     if (t2.kind === SyntaxKind.BlockStart) {
-      this.getToken();
       members = [];
       for (;;) {
         const t3 = this.peekToken();
@@ -499,9 +510,12 @@ export class Parser {
         const member = new StructDeclarationField(name, colon, typeExpr);
         members.push(member);
       }
+      t2 = this.getToken();
     }
-    this.expectToken(SyntaxKind.LineFoldEnd);
-    return new StructDeclaration(pubKeyword, t0, name, members);
+    if (t2.kind !== SyntaxKind.LineFoldEnd) {
+      this.raiseParseError(t2, [ SyntaxKind.LineFoldEnd, SyntaxKind.BlockStart, SyntaxKind.Identifier ]);
+    }
+    return new StructDeclaration(pubKeyword, t0, name, typeVars, members);
   }
 
   private parsePatternStartingWithConstructor() {