compiler: more work along the lines of generics

compiler/ast.ts

@@ -15,7 +15,7 @@ export type StmtKind =
     | {
         type: "fn";
         ident: string;
-        etypeParams?: ETypeParam[];
+        genericParams?: GenericParam[];
         params: Param[];
         returnType?: EType;
         body: Expr;
@@ -39,13 +39,18 @@ export type ExprKind =
     | { type: "error" }
     | { type: "int"; value: number }
     | { type: "string"; value: string }
-    | { type: "ident"; value: string }
+    | { type: "ident"; ident: string }
+    | {
+        type: "sym";
+        ident: string;
+        sym: Sym;
+    }
     | { type: "group"; expr: Expr }
-    | { type: "field"; subject: Expr; value: string }
+    | { type: "field"; subject: Expr; ident: string }
     | { type: "index"; subject: Expr; value: Expr }
-    | { type: "call"; subject: Expr; etypeArgs?: EType[]; args: Expr[] }
+    | { type: "call"; subject: Expr; args: Expr[] }
-    | { type: "path"; subject: Expr; value: string }
+    | { type: "path"; subject: Expr; ident: string }
-    | { type: "etype_args"; subject: Expr; etypeArgs?: EType[] }
+    | { type: "etype_args"; subject: Expr; etypeArgs: EType[] }
     | { type: "unary"; unaryType: UnaryType; subject: Expr }
     | { type: "binary"; binaryType: BinaryType; left: Expr; right: Expr }
     | { type: "if"; cond: Expr; truthy: Expr; falsy?: Expr; elsePos?: Pos }
@@ -53,11 +58,6 @@ export type ExprKind =
     | { type: "null" }
     | { type: "loop"; body: Expr }
     | { type: "block"; stmts: Stmt[]; expr?: Expr }
-    | {
-        type: "sym";
-        ident: string;
-        sym: Sym;
-    }
     | { type: "while"; cond: Expr; body: Expr }
     | { type: "for_in"; param: Param; value: Expr; body: Expr }
     | {
@@ -101,7 +101,7 @@ export type SymKind =
     | { type: "fn"; stmt: Stmt }
     | { type: "fn_param"; param: Param }
     | { type: "closure"; inner: Sym }
-    | { type: "generic"; etypeParam: ETypeParam };
+    | { type: "generic"; genericParam: GenericParam };
 
 export type EType = {
     kind: ETypeKind;
@@ -111,11 +111,20 @@ export type EType = {
 
 export type ETypeKind =
     | { type: "error" }
-    | { type: "ident"; value: string }
+    | { type: "null" }
+    | { type: "int" }
+    | { type: "bool" }
+    | { type: "string" }
+    | { type: "ident"; ident: string }
+    | {
+        type: "sym";
+        ident: string;
+        sym: Sym;
+    }
     | { type: "array"; inner: EType }
     | { type: "struct"; fields: Param[] };
 
-export type ETypeParam = {
+export type GenericParam = {
     ident: string;
     pos: Pos;
     vtype?: VType;

compiler/ast_visitor.ts

@@ -22,6 +22,8 @@ export interface AstVisitor<Args extends unknown[] = []> {
     visitFieldExpr?(expr: Expr, ...args: Args): VisitRes;
     visitIndexExpr?(expr: Expr, ...args: Args): VisitRes;
     visitCallExpr?(expr: Expr, ...args: Args): VisitRes;
+    visitPathExpr?(expr: Expr, ...args: Args): VisitRes;
+    visitETypeArgsExpr?(expr: Expr, ...args: Args): VisitRes;
     visitUnaryExpr?(expr: Expr, ...args: Args): VisitRes;
     visitBinaryExpr?(expr: Expr, ...args: Args): VisitRes;
     visitIfExpr?(expr: Expr, ...args: Args): VisitRes;
@@ -36,7 +38,12 @@ export interface AstVisitor<Args extends unknown[] = []> {
     visitParam?(param: Param, ...args: Args): VisitRes;
     visitEType?(etype: EType, ...args: Args): VisitRes;
     visitErrorEType?(etype: EType, ...args: Args): VisitRes;
+    visitNullEType?(etype: EType, ...args: Args): VisitRes;
+    visitIntEType?(etype: EType, ...args: Args): VisitRes;
+    visitBoolEType?(etype: EType, ...args: Args): VisitRes;
+    visitStringEType?(etype: EType, ...args: Args): VisitRes;
     visitIdentEType?(etype: EType, ...args: Args): VisitRes;
+    visitSymEType?(etype: EType, ...args: Args): VisitRes;
     visitArrayEType?(etype: EType, ...args: Args): VisitRes;
     visitStructEType?(etype: EType, ...args: Args): VisitRes;
     visitAnno?(etype: EType, ...args: Args): VisitRes;
@@ -95,6 +102,12 @@ export function visitStmt<Args extends unknown[] = []>(
             if (v.visitExprStmt?.(stmt, ...args) == "stop") return;
             visitExpr(stmt.kind.expr, v, ...args);
             break;
+        default:
+            throw new Error(
+                `statement '${
+                    (stmt.kind as { type: string }).type
+                }' not implemented`,
+            );
     }
 }
 
@@ -135,6 +148,15 @@ export function visitExpr<Args extends unknown[] = []>(
             visitExpr(expr.kind.subject, v, ...args);
             expr.kind.args.map((arg) => visitExpr(arg, v, ...args));
             break;
+        case "path":
+            if (v.visitPathExpr?.(expr, ...args) == "stop") return;
+            visitExpr(expr.kind.subject, v, ...args);
+            break;
+        case "etype_args":
+            if (v.visitETypeArgsExpr?.(expr, ...args) == "stop") return;
+            visitExpr(expr.kind.subject, v, ...args);
+            expr.kind.etypeArgs.map((arg) => visitEType(arg, v, ...args));
+            break;
         case "unary":
             if (v.visitUnaryExpr?.(expr, ...args) == "stop") return;
             visitExpr(expr.kind.subject, v, ...args);
@@ -186,6 +208,12 @@ export function visitExpr<Args extends unknown[] = []>(
         case "sym":
             if (v.visitSymExpr?.(expr, ...args) == "stop") return;
             break;
+        default:
+            throw new Error(
+                `expression '${
+                    (expr.kind as { type: string }).type
+                }' not implemented`,
+            );
     }
 }
 
@@ -208,9 +236,24 @@ export function visitEType<Args extends unknown[] = []>(
         case "error":
             if (v.visitErrorEType?.(etype, ...args) == "stop") return;
             break;
+        case "string":
+            if (v.visitStringEType?.(etype, ...args) == "stop") return;
+            break;
+        case "null":
+            if (v.visitNullEType?.(etype, ...args) == "stop") return;
+            break;
+        case "int":
+            if (v.visitIntEType?.(etype, ...args) == "stop") return;
+            break;
+        case "bool":
+            if (v.visitBoolEType?.(etype, ...args) == "stop") return;
+            break;
         case "ident":
             if (v.visitIdentEType?.(etype, ...args) == "stop") return;
             break;
+        case "sym":
+            if (v.visitSymEType?.(etype, ...args) == "stop") return;
+            break;
         case "array":
             if (v.visitArrayEType?.(etype, ...args) == "stop") return;
             if (etype.kind.inner) visitEType(etype.kind.inner, v, ...args);
@@ -219,6 +262,12 @@ export function visitEType<Args extends unknown[] = []>(
             if (v.visitStructEType?.(etype, ...args) == "stop") return;
             etype.kind.fields.map((field) => visitParam(field, v, ...args));
             break;
+        default:
+            throw new Error(
+                `etype '${
+                    (etype.kind as { type: string }).type
+                }' not implemented`,
+            );
     }
 }
 

compiler/checker.ts

@@ -1,7 +1,13 @@
 import { EType, Expr, Stmt } from "./ast.ts";
 import { printStackTrace, Reporter } from "./info.ts";
 import { Pos } from "./token.ts";
-import { VType, VTypeParam, vtypesEqual, vtypeToString } from "./vtype.ts";
+import {
+    VType,
+    VTypeGenericParam,
+    VTypeParam,
+    vtypesEqual,
+    vtypeToString,
+} from "./vtype.ts";
 
 export class Checker {
     private fnReturnStack: VType[] = [];
@@ -24,6 +30,13 @@ export class Checker {
             const returnType: VType = stmt.kind.returnType
                 ? this.checkEType(stmt.kind.returnType)
                 : { type: "null" };
+            let genericParams: VTypeGenericParam[] | undefined;
+            if (stmt.kind.genericParams !== undefined) {
+                genericParams = [];
+                for (const etypeParam of stmt.kind.genericParams) {
+                    genericParams.push({ ident: etypeParam.ident });
+                }
+            }
             const params: VTypeParam[] = [];
             for (const param of stmt.kind.params) {
                 if (param.etype === undefined) {
@@ -34,7 +47,7 @@ export class Checker {
                 param.vtype = vtype;
                 params.push({ ident: param.ident, vtype });
             }
-            stmt.kind.vtype = { type: "fn", params, returnType };
+            stmt.kind.vtype = { type: "fn", genericParams, params, returnType };
         }
     }
 
@@ -178,13 +191,13 @@ export class Checker {
                     this.report("cannot use field on non-struct", pos);
                     return { type: "error" };
                 }
-                const fieldValue = stmt.kind.subject.kind.value;
+                const fieldValue = stmt.kind.subject.kind.ident;
                 const found = subject.fields.find((param) =>
                     param.ident === fieldValue
                 );
                 if (!found) {
                     this.report(
-                        `no field named '${stmt.kind.subject.kind.value}' on struct`,
+                        `no field named '${stmt.kind.subject.kind.ident}' on struct`,
                         pos,
                     );
                     return { type: "error" };
@@ -281,6 +294,10 @@ export class Checker {
                     return this.checkIndexExpr(expr);
                 case "call":
                     return this.checkCallExpr(expr);
+                case "path":
+                    return this.checkPathExpr(expr);
+                case "etype_args":
+                    return this.checkETypeArgsExpr(expr);
                 case "unary":
                     return this.checkUnaryExpr(expr);
                 case "binary":
@@ -324,9 +341,9 @@ export class Checker {
             }
             case "fn_param":
                 return expr.kind.sym.param.vtype!;
-            case "builtin":
             case "let_static":
             case "closure":
+            case "generic":
                 throw new Error(
                     `not implemented, sym type '${expr.kind.sym.type}'`,
                 );
@@ -343,11 +360,11 @@ export class Checker {
             this.report("cannot use field on non-struct", pos);
             return { type: "error" };
         }
-        const value = expr.kind.value;
+        const value = expr.kind.ident;
         const found = subject.fields.find((param) => param.ident === value);
         if (!found) {
             this.report(
-                `no field named '${expr.kind.value}' on struct`,
+                `no field named '${expr.kind.ident}' on struct`,
                 pos,
             );
             return { type: "error" };
@@ -408,6 +425,43 @@ export class Checker {
         return subject.returnType;
     }
 
+    public checkPathExpr(expr: Expr): VType {
+        if (expr.kind.type !== "path") {
+            throw new Error();
+        }
+        throw new Error("not implemented");
+    }
+
+    public checkETypeArgsExpr(expr: Expr): VType {
+        if (expr.kind.type !== "etype_args") {
+            throw new Error();
+        }
+        const pos = expr.pos;
+        const subject = this.checkExpr(expr.kind.subject);
+        if (subject.type !== "fn" || subject.genericParams === undefined) {
+            this.report(
+                "etype arguments must only be applied to generic functions",
+                expr.pos,
+            );
+            return { type: "error" };
+        }
+        const genericParams = expr.kind.etypeArgs.map((arg) =>
+            this.checkEType(arg)
+        );
+        if (genericParams.length !== subject.params.length) {
+            this.report(
+                `incorrect number of arguments` +
+                    `, expected ${subject.params.length}`,
+                pos,
+            );
+        }
+        return {
+            type: "generic_spec",
+            subject,
+            genericParams,
+        };
+    }
+
     public checkUnaryExpr(expr: Expr): VType {
         if (expr.kind.type !== "unary") {
             throw new Error();
@@ -556,20 +610,25 @@ export class Checker {
 
     public checkEType(etype: EType): VType {
         const pos = etype.pos;
-        if (etype.kind.type === "ident") {
+        switch (etype.kind.type) {
-            if (etype.kind.value === "null") {
+            case "null":
                 return { type: "null" };
-            }
+            case "int":
-            if (etype.kind.value === "int") {
                 return { type: "int" };
-            }
+            case "bool":
-            if (etype.kind.value === "bool") {
                 return { type: "bool" };
-            }
+            case "string":
-            if (etype.kind.value === "string") {
                 return { type: "string" };
+        }
+        if (etype.kind.type === "ident") {
+            this.report(`undefined type '${etype.kind.ident}'`, pos);
+            return { type: "error" };
+        }
+        if (etype.kind.type === "sym") {
+            if (etype.kind.sym.type === "generic") {
+                return { type: "generic" };
             }
-            this.report(`undefined type '${etype.kind.value}'`, pos);
+            this.report(`sym type '${etype.kind.sym.type}' used as type`, pos);
             return { type: "error" };
         }
         if (etype.kind.type === "array") {

compiler/desugar/special_loop.ts

@@ -80,12 +80,12 @@ export class SpecialLoopDesugarer implements AstVisitor {
                         type: "call",
                         subject: Expr({
                             type: "ident",
-                            value: "int_array_length",
+                            ident: "int_array_length",
                         }),
                         args: [
                             Expr({
                                 type: "ident",
-                                value: "::values",
+                                ident: "::values",
                             }),
                         ],
                     }),
@@ -114,11 +114,11 @@ export class SpecialLoopDesugarer implements AstVisitor {
                                                 binaryType: "<",
                                                 left: Expr({
                                                     type: "ident",
-                                                    value: "::index",
+                                                    ident: "::index",
                                                 }),
                                                 right: Expr({
                                                     type: "ident",
-                                                    value: "::length",
+                                                    ident: "::length",
                                                 }),
                                             }),
                                         }),
@@ -139,11 +139,11 @@ export class SpecialLoopDesugarer implements AstVisitor {
                                         type: "index",
                                         subject: Expr({
                                             type: "ident",
-                                            value: "::values",
+                                            ident: "::values",
                                         }),
                                         value: Expr({
                                             type: "ident",
-                                            value: "::index",
+                                            ident: "::index",
                                         }),
                                     }),
                                 }, expr.pos),
@@ -156,7 +156,7 @@ export class SpecialLoopDesugarer implements AstVisitor {
                                     assignType: "+=",
                                     subject: Expr({
                                         type: "ident",
-                                        value: "::index",
+                                        ident: "::index",
                                     }),
                                     value: Expr({
                                         type: "int",

compiler/lexer.ts

@@ -36,15 +36,18 @@ export class Lexer {
                 "else",
                 "struct",
                 "import",
-                "false",
-                "true",
-                "null",
                 "or",
                 "and",
                 "not",
                 "while",
                 "for",
                 "in",
+                "false",
+                "true",
+                "null",
+                "int",
+                "bool",
+                "string",
             ];
             if (keywords.includes(value)) {
                 return this.token(value, pos);

compiler/lowerer.ts

@@ -107,7 +107,7 @@ export class Lowerer {
         switch (stmt.kind.subject.kind.type) {
             case "field": {
                 this.lowerExpr(stmt.kind.subject.kind.subject);
-                this.program.add(Ops.PushString, stmt.kind.subject.kind.value);
+                this.program.add(Ops.PushString, stmt.kind.subject.kind.ident);
                 this.program.add(Ops.Builtin, Builtins.StructSet);
                 return;
             }
@@ -209,7 +209,7 @@ export class Lowerer {
                 `unexpected argument type '${anno.kind.type}' expected 'ident'`,
             );
         }
-        const value = anno.kind.value;
+        const value = anno.kind.ident;
         const builtin = Object.entries(Builtins).find((entry) =>
             entry[0] === value
         )?.[1];

compiler/parser.ts

@@ -5,9 +5,9 @@ import {
     BinaryType,
     EType,
     ETypeKind,
-    ETypeParam,
     Expr,
     ExprKind,
+    GenericParam,
     Param,
     Stmt,
     StmtKind,
@@ -175,9 +175,9 @@ export class Parser {
         }
         const ident = this.current().identValue!;
         this.step();
-        let etypeParams: ETypeParam[] | undefined;
+        let genericParams: GenericParam[] | undefined;
         if (this.test("<")) {
-            etypeParams = this.parseFnETypeParams();
+            genericParams = this.parseFnETypeParams();
         }
         if (!this.test("(")) {
             this.report("expected '('");
@@ -207,7 +207,7 @@ export class Parser {
             {
                 type: "fn",
                 ident,
-                etypeParams,
+                genericParams,
                 params,
                 returnType,
                 body,
@@ -265,11 +265,11 @@ export class Parser {
         return { ok: true, value: { ident, pos, values } };
     }
 
-    private parseFnETypeParams(): ETypeParam[] {
+    private parseFnETypeParams(): GenericParam[] {
         return this.parseDelimitedList(this.parseETypeParam, ">", ",");
     }
 
-    private parseETypeParam(): Res<ETypeParam> {
+    private parseETypeParam(): Res<GenericParam> {
         const pos = this.pos();
         if (this.test("ident")) {
             const ident = this.current().identValue!;
@@ -627,71 +627,24 @@ export class Parser {
     private parsePostfix(): Expr {
         let subject = this.parseOperand();
         while (true) {
-            const pos = this.pos();
             if (this.test(".")) {
-                this.step();
+                subject = this.parseFieldTail(subject);
-                if (!this.test("ident")) {
-                    this.report("expected ident");
-                    return this.expr({ type: "error" }, pos);
-                }
-                const value = this.current().identValue!;
-                this.step();
-                subject = this.expr({ type: "field", subject, value }, pos);
                 continue;
             }
             if (this.test("[")) {
-                this.step();
+                subject = this.parseIndexTail(subject);
-                const value = this.parseExpr();
-                if (!this.test("]")) {
-                    this.report("expected ']'");
-                    return this.expr({ type: "error" }, pos);
-                }
-                this.step();
-                subject = this.expr({ type: "index", subject, value }, pos);
                 continue;
             }
             if (this.test("(")) {
-                const args = this.parseDelimitedList(
+                subject = this.parseCallTail(subject);
-                    this.parseExprArg,
-                    ")",
-                    ",",
-                );
-                subject = this.expr({ type: "call", subject, args }, pos);
                 continue;
             }
             if (this.test("::")) {
-                this.step();
+                subject = this.parsePathTail(subject);
-                if (!this.test("ident")) {
-                    this.report("expected ident");
-                    return this.expr({ type: "error" }, pos);
-                }
-                const value = this.current().identValue!;
-                this.step();
-                subject = this.expr({ type: "path", subject, value }, pos);
                 continue;
             }
             if (this.test("::<")) {
-                const etypeArgs = this.parseDelimitedList(
+                subject = this.parseETypeArgsTail(subject);
-                    this.parseETypeArg,
-                    ">",
-                    ",",
-                );
-                if (this.test("(")) {
-                    subject = this.expr(
-                        { type: "etype_args", subject, etypeArgs },
-                        pos,
-                    );
-                    continue;
-                }
-                const args = this.parseDelimitedList(
-                    this.parseExprArg,
-                    ")",
-                    ",",
-                );
-                subject = this.expr(
-                    { type: "call", subject, etypeArgs, args },
-                    pos,
-                );
                 continue;
             }
             break;
@@ -699,6 +652,65 @@ export class Parser {
         return subject;
     }
 
+    private parseETypeArgsTail(subject: Expr): Expr {
+        const pos = this.pos();
+        const etypeArgs = this.parseDelimitedList(
+            this.parseETypeArg,
+            ">",
+            ",",
+        );
+        return this.expr(
+            { type: "etype_args", subject, etypeArgs },
+            pos,
+        );
+    }
+
+    private parseFieldTail(subject: Expr): Expr {
+        const pos = this.pos();
+        this.step();
+        if (!this.test("ident")) {
+            this.report("expected ident");
+            return this.expr({ type: "error" }, pos);
+        }
+        const ident = this.current().identValue!;
+        this.step();
+        return this.expr({ type: "field", subject, ident }, pos);
+    }
+
+    private parseIndexTail(subject: Expr): Expr {
+        const pos = this.pos();
+        this.step();
+        const value = this.parseExpr();
+        if (!this.test("]")) {
+            this.report("expected ']'");
+            return this.expr({ type: "error" }, pos);
+        }
+        this.step();
+        return this.expr({ type: "index", subject, value }, pos);
+    }
+
+    private parseCallTail(subject: Expr): Expr {
+        const pos = this.pos();
+        const args = this.parseDelimitedList(
+            this.parseExprArg,
+            ")",
+            ",",
+        );
+        return this.expr({ type: "call", subject, args }, pos);
+    }
+
+    private parsePathTail(subject: Expr): Expr {
+        const pos = this.pos();
+        this.step();
+        if (!this.test("ident")) {
+            this.report("expected ident");
+            return this.expr({ type: "error" }, pos);
+        }
+        const ident = this.current().identValue!;
+        this.step();
+        return this.expr({ type: "path", subject, ident }, pos);
+    }
+
     private parseExprArg(): Res<Expr> {
         return { ok: true, value: this.parseExpr() };
     }
@@ -710,9 +722,9 @@ export class Parser {
     private parseOperand(): Expr {
         const pos = this.pos();
         if (this.test("ident")) {
-            const value = this.current().identValue!;
+            const ident = this.current().identValue!;
             this.step();
-            return this.expr({ type: "ident", value }, pos);
+            return this.expr({ type: "ident", ident }, pos);
         }
         if (this.test("int")) {
             const value = this.current().intValue!;
@@ -763,10 +775,19 @@ export class Parser {
 
     private parseEType(): EType {
         const pos = this.pos();
+        if (["null", "int", "bool", "string"].includes(this.current().type)) {
+            const type = this.current().type as
+                | "null"
+                | "int"
+                | "bool"
+                | "string";
+            this.step();
+            return this.etype({ type }, pos);
+        }
         if (this.test("ident")) {
             const ident = this.current().identValue!;
             this.step();
-            return this.etype({ type: "ident", value: ident }, pos);
+            return this.etype({ type: "ident", ident: ident }, pos);
         }
         if (this.test("[")) {
             this.step();

compiler/resolver.ts

@@ -1,7 +1,9 @@
-import { Expr, Stmt } from "./ast.ts";
+import { EType, Expr, Stmt } from "./ast.ts";
 import {
     AstVisitor,
+    visitEType,
     visitExpr,
+    visitParam,
     VisitRes,
     visitStmt,
     visitStmts,
@@ -73,7 +75,7 @@ export class Resolver implements AstVisitor<[Syms]> {
             throw new Error("expected fn statement");
         }
         const fnScopeSyms = new FnSyms(syms);
-        for (const param of stmt.kind.etypeParams ?? []) {
+        for (const param of stmt.kind.genericParams ?? []) {
             if (fnScopeSyms.definedLocally(param.ident)) {
                 this.reportAlreadyDefined(param.ident, param.pos, syms);
                 continue;
@@ -82,7 +84,7 @@ export class Resolver implements AstVisitor<[Syms]> {
                 ident: param.ident,
                 type: "generic",
                 pos: param.pos,
-                etypeParam: param,
+                genericParam: param,
             });
         }
         for (const param of stmt.kind.params) {
@@ -90,6 +92,7 @@ export class Resolver implements AstVisitor<[Syms]> {
                 this.reportAlreadyDefined(param.ident, param.pos, syms);
                 continue;
             }
+            visitParam(param, this, fnScopeSyms);
             fnScopeSyms.define(param.ident, {
                 ident: param.ident,
                 type: "fn_param",
@@ -97,6 +100,9 @@ export class Resolver implements AstVisitor<[Syms]> {
                 param,
             });
         }
+        if (stmt.kind.returnType) {
+            visitEType(stmt.kind.returnType, this, fnScopeSyms);
+        }
         visitExpr(stmt.kind.body, this, fnScopeSyms);
         return "stop";
     }
@@ -105,18 +111,14 @@ export class Resolver implements AstVisitor<[Syms]> {
         if (expr.kind.type !== "ident") {
             throw new Error("expected ident");
         }
-        const ident = expr.kind;
+        const ident = expr.kind.ident;
-        const symResult = syms.get(ident.value);
+        const symResult = syms.get(ident);
         if (!symResult.ok) {
-            this.reportUseOfUndefined(ident.value, expr.pos, syms);
+            this.reportUseOfUndefined(ident, expr.pos, syms);
             return;
         }
         const sym = symResult.sym;
-        expr.kind = {
+        expr.kind = { type: "sym", ident, sym };
-            type: "sym",
-            ident: ident.value,
-            sym,
-        };
         return "stop";
     }
 
@@ -146,6 +148,21 @@ export class Resolver implements AstVisitor<[Syms]> {
         return "stop";
     }
 
+    visitIdentEType(etype: EType, syms: Syms): VisitRes {
+        if (etype.kind.type !== "ident") {
+            throw new Error();
+        }
+        const ident = etype.kind.ident;
+        const symResult = syms.get(ident);
+        if (!symResult.ok) {
+            this.reportUseOfUndefined(ident, etype.pos, syms);
+            return;
+        }
+        const sym = symResult.sym;
+        etype.kind = { type: "sym", ident, sym };
+        return "stop";
+    }
+
     private reportUseOfUndefined(ident: string, pos: Pos, _syms: Syms) {
         this.reporter.reportError({
             reporter: "Resolver",

compiler/vtype.ts

@@ -7,13 +7,28 @@ export type VType =
     | { type: "bool" }
     | { type: "array"; inner: VType }
     | { type: "struct"; fields: VTypeParam[] }
-    | { type: "fn"; params: VTypeParam[]; returnType: VType };
+    | {
+        type: "fn";
+        genericParams?: VTypeGenericParam[];
+        params: VTypeParam[];
+        returnType: VType;
+    }
+    | { type: "generic" }
+    | {
+        type: "generic_spec";
+        subject: VType;
+        genericParams: VType[];
+    };
 
 export type VTypeParam = {
     ident: string;
     vtype: VType;
 };
 
+export type VTypeGenericParam = {
+    ident: string;
+};
+
 export function vtypesEqual(a: VType, b: VType): boolean {
     if (a.type !== b.type) {
         return false;
@@ -58,5 +73,8 @@ export function vtypeToString(vtype: VType): string {
             .join(", ");
         return `fn (${paramString}) -> ${vtypeToString(vtype.returnType)}`;
     }
+    if (vtype.type === "generic") {
+        return `generic`;
+    }
     throw new Error(`unhandled vtype '${vtype.type}'`);
 }