diff --git a/compiler/ast.ts b/compiler/ast.ts
index c9d81f0..1a3901d 100644
--- a/compiler/ast.ts
+++ b/compiler/ast.ts
@@ -111,6 +111,8 @@ export type Field = {
 };
 
 export type Param = {
+    id: number;
+    index?: number;
     ident: string;
     etype?: EType;
     pos: Pos;
@@ -156,6 +158,7 @@ export type ETypeKind =
 
 export type GenericParam = {
     id: number;
+    index: number;
     ident: string;
     pos: Pos;
     vtype?: VType;
@@ -171,21 +174,34 @@ export class AstCreator {
     private nextNodeId = 0;
 
     public stmt(kind: StmtKind, pos: Pos, details?: StmtDetails): Stmt {
-        const id = this.nextNodeId;
-        this.nextNodeId += 1;
+        const id = this.genId();
         return { kind, pos, details, id };
     }
 
     public expr(kind: ExprKind, pos: Pos): Expr {
-        const id = this.nextNodeId;
-        this.nextNodeId += 1;
+        const id = this.genId();
         return { kind, pos, id };
     }
 
     public etype(kind: ETypeKind, pos: Pos): EType {
+        const id = this.genId();
+        return { kind, pos, id };
+    }
+
+    public param(val: Omit<Param, "id">): Param {
+        const id = this.genId();
+        return { ...val, id };
+    }
+
+    public genericParam(val: Omit<GenericParam, "id">): GenericParam {
+        const id = this.genId();
+        return { ...val, id };
+    }
+
+    private genId(): number {
         const id = this.nextNodeId;
         this.nextNodeId += 1;
-        return { kind, pos, id };
+        return id;
     }
 }
 
diff --git a/compiler/parser.ts b/compiler/parser.ts
index 03f6fbd..98b5c66 100644
--- a/compiler/parser.ts
+++ b/compiler/parser.ts
@@ -330,16 +330,15 @@ export class Parser {
         return this.parseDelimitedList(this.parseETypeParam, ">", ",");
     }
 
-    private veryTemporaryETypeParamIdCounter = 0;
-
-    private parseETypeParam(): Res<GenericParam> {
+    private parseETypeParam(index: number): Res<GenericParam> {
         const pos = this.pos();
         if (this.test("ident")) {
             const ident = this.current().identValue!;
             this.step();
-            const id = this.veryTemporaryETypeParamIdCounter;
-            this.veryTemporaryETypeParamIdCounter += 1;
-            return { ok: true, value: { id, ident, pos } };
+            return {
+                ok: true,
+                value: this.astCreator.genericParam({ index, ident, pos }),
+            };
         }
         this.report("expected generic parameter");
         return { ok: false };
@@ -350,7 +349,7 @@ export class Parser {
     }
 
     private parseDelimitedList<T>(
-        parseElem: (this: Parser) => Res<T>,
+        parseElem: (this: Parser, index: number) => Res<T>,
         endToken: string,
         delimiter: string,
     ): T[] {
@@ -359,8 +358,9 @@ export class Parser {
             this.step();
             return [];
         }
+        let i = 0;
         const elems: T[] = [];
-        const elemRes = parseElem.call(this);
+        const elemRes = parseElem.call(this, i);
         if (!elemRes.ok) {
             return [];
         }
@@ -370,7 +370,7 @@ export class Parser {
             if (this.test(endToken)) {
                 break;
             }
-            const elemRes = parseElem.call(this);
+            const elemRes = parseElem.call(this, i);
             if (!elemRes.ok) {
                 return [];
             }
@@ -384,7 +384,7 @@ export class Parser {
         return elems;
     }
 
-    private parseParam(): Res<Param> {
+    private parseParam(index?: number): Res<Param> {
         const pos = this.pos();
         if (this.test("ident")) {
             const ident = this.current().identValue!;
@@ -392,9 +392,15 @@ export class Parser {
             if (this.test(":")) {
                 this.step();
                 const etype = this.parseEType();
-                return { ok: true, value: { ident, etype, pos } };
+                return {
+                    ok: true,
+                    value: this.astCreator.param({ index, ident, etype, pos }),
+                };
             }
-            return { ok: true, value: { ident, pos } };
+            return {
+                ok: true,
+                value: this.astCreator.param({ index, ident, pos }),
+            };
         }
         this.report("expected param");
         return { ok: false };