diff --git a/src/ast.ts b/src/ast.ts
index 9b6e15e..05f6b9d 100644
--- a/src/ast.ts
+++ b/src/ast.ts
@@ -1,29 +1,31 @@
+import { Loc } from "./diagnostics.ts";
+
 export function create<Tag extends NodeKind["tag"]>(
-    line: number,
+    loc: Loc,
     tag: Tag,
     kind: Omit<NodeKind & { tag: Tag }, "tag">,
 ): Node {
-    return Node.create(line, tag, kind);
+    return Node.create(loc, tag, kind);
 }
 
 export class Node {
     private static idCounter = 0;
 
     static create<Tag extends NodeKind["tag"]>(
-        line: number,
+        loc: Loc,
         tag: Tag,
         kind: Omit<NodeKind & { tag: Tag }, "tag">,
     ): Node {
         return new Node(
             Node.idCounter++,
-            line,
+            loc,
             { tag, ...kind } as NodeKind & { tag: Tag },
         );
     }
 
     private constructor(
         public id: number,
-        public line: number,
+        public loc: Loc,
         public kind: NodeKind,
     ) {}
 
diff --git a/src/diagnostics.ts b/src/diagnostics.ts
index 4d7b245..b0e2e9c 100644
--- a/src/diagnostics.ts
+++ b/src/diagnostics.ts
@@ -15,11 +15,13 @@ export type FileInfo = {
 
 export function printDiagnostics(
     filename: string,
-    line: number,
+    loc: Loc,
     severity: "error" | "info",
     message: string,
     text?: string,
 ) {
+    const line = loc.line;
+
     const severityColor = ({
         "error": "red",
         "info": "blue",
diff --git a/src/front/check.ts b/src/front/check.ts
index 3f503f9..c5281c6 100644
--- a/src/front/check.ts
+++ b/src/front/check.ts
@@ -1,5 +1,5 @@
 import * as ast from "../ast.ts";
-import { printDiagnostics } from "../diagnostics.ts";
+import { Loc, printDiagnostics } from "../diagnostics.ts";
 import { Ty } from "../ty.ts";
 import { builtins } from "./builtins.ts";
 import { ResolveMap } from "./resolve.ts";
@@ -46,14 +46,14 @@ export class Checker {
                     this.assertCompatible(
                         exprTy,
                         explicitTy,
-                        sym.stmt.kind.expr.line,
+                        sym.stmt.kind.expr.loc,
                     );
                 }
                 return exprTy;
             }
             if (sym.tag === "FnParam") {
                 if (!node.kind.ty) {
-                    this.error(node.line, `parameter must have a type`);
+                    this.error(node.loc, `parameter must have a type`);
                     this.fail();
                 }
                 return this.check(node.kind.ty);
@@ -91,13 +91,13 @@ export class Checker {
             for (const value of node.kind.values) {
                 const valueTy = this.check(value);
                 if (ty) {
-                    this.assertCompatible(ty, valueTy, value.line);
+                    this.assertCompatible(ty, valueTy, value.loc);
                 } else {
                     ty = valueTy;
                 }
             }
             if (!ty) {
-                this.error(node.line, `could not infer type of empty array`);
+                this.error(node.loc, `could not infer type of empty array`);
                 this.fail();
             }
             const length = node.kind.values.length;
@@ -120,7 +120,7 @@ export class Checker {
                 return Ty.create("Slice", { ty: exprTy.kind.ty });
             }
             this.error(
-                node.line,
+                node.loc,
                 `cannot use index operator on '${exprTy.pretty()}' with '${argTy.pretty()}'`,
             );
             this.fail();
@@ -150,7 +150,7 @@ export class Checker {
                 }
             }
             this.error(
-                node.line,
+                node.loc,
                 `operator '${node.kind.tok}' cannot be applied to type '${exprTy.pretty()}'`,
             );
             this.fail();
@@ -167,7 +167,7 @@ export class Checker {
                 );
             if (!binaryOp) {
                 this.error(
-                    node.line,
+                    node.loc,
                     `operator '${node.kind.tok}' cannot be applied to types '${left.pretty()}' and '${right.pretty()}'`,
                 );
                 this.fail();
@@ -180,7 +180,7 @@ export class Checker {
                 const operandTy = operandExpr && this.check(operandExpr);
                 if (operandTy && !operandTy.compatibleWith(Ty.Int)) {
                     this.error(
-                        operandExpr.line,
+                        operandExpr.loc,
                         `range operand must be '${Ty.Int.pretty()}', not '${operandTy.pretty()}'`,
                     );
                     this.fail();
@@ -198,7 +198,7 @@ export class Checker {
                 case "bool":
                     return Ty.Bool;
                 default:
-                    this.error(node.line, `unknown type '${node.kind.ident}'`);
+                    this.error(node.loc, `unknown type '${node.kind.ident}'`);
             }
         }
 
@@ -216,14 +216,14 @@ export class Checker {
             const lengthTy = this.check(node.kind.length);
             if (!lengthTy.compatibleWith(Ty.Int)) {
                 this.error(
-                    node.kind.length.line,
+                    node.kind.length.loc,
                     `for array length, expected 'int', got '${lengthTy.pretty()}'`,
                 );
                 this.fail();
             }
             if (!node.kind.length.is("IntExpr")) {
                 this.error(
-                    node.kind.length.line,
+                    node.kind.length.loc,
                     `array length must be an 'int' expression`,
                 );
                 this.fail();
@@ -254,11 +254,11 @@ export class Checker {
                         : Ty.Void;
                     if (!ty.compatibleWith(retTy)) {
                         this.error(
-                            node.line,
+                            node.loc,
                             `type '${ty.pretty()}' not compatible with return type '${retTy.pretty()}'`,
                         );
                         this.info(
-                            stmt.kind.retTy?.line ?? stmt.line,
+                            stmt.kind.retTy?.loc ?? stmt.loc,
                             `return type '${retTy}' defined here`,
                         );
                         this.fail();
@@ -282,7 +282,7 @@ export class Checker {
 
         if (!callableTy) {
             this.error(
-                node.line,
+                node.loc,
                 `type '${calleeTy.pretty()}' not callable`,
             );
             this.fail();
@@ -293,12 +293,12 @@ export class Checker {
         const params = callableTy.kind.params;
         if (args.length !== params.length) {
             this.error(
-                node.line,
+                node.loc,
                 `incorrect amount of arguments. got ${args.length} expected ${params.length}`,
             );
             if (calleeTy.is("FnStmt")) {
                 this.info(
-                    calleeTy.kind.stmt.line,
+                    calleeTy.kind.stmt.loc,
                     "function defined here",
                 );
             }
@@ -307,14 +307,14 @@ export class Checker {
         for (const i of args.keys()) {
             if (!args[i].compatibleWith(params[i])) {
                 this.error(
-                    node.kind.args[i].line,
+                    node.kind.args[i].loc,
                     `type '${args[i].pretty()}' not compatible with type '${
                         params[i].pretty()
                     }', for argument ${i}`,
                 );
                 if (calleeTy.is("FnStmt")) {
                     this.info(
-                        calleeTy.kind.stmt.kind.params[i].line,
+                        calleeTy.kind.stmt.kind.params[i].loc,
                         `parameter '${
                             calleeTy.kind.stmt.kind.params[i]
                                 .as("Param").kind.ident
@@ -327,30 +327,30 @@ export class Checker {
         return callableTy.kind.retTy;
     }
 
-    private assertCompatible(left: Ty, right: Ty, line: number): void {
+    private assertCompatible(left: Ty, right: Ty, loc: Loc): void {
         if (!left.compatibleWith(right)) {
             this.error(
-                line,
+                loc,
                 `type '${left.pretty()}' not compatible with type '${right.pretty()}'`,
             );
             this.fail();
         }
     }
 
-    private error(line: number, message: string) {
+    private error(loc: Loc, message: string) {
         printDiagnostics(
             this.filename,
-            line,
+            loc,
             "error",
             message,
             this.text,
         );
     }
 
-    private info(line: number, message: string) {
+    private info(loc: Loc, message: string) {
         printDiagnostics(
             this.filename,
-            line,
+            loc,
             "info",
             message,
             this.text,
diff --git a/src/front/parse.ts b/src/front/parse.ts
index 7d52acb..b50f90d 100644
--- a/src/front/parse.ts
+++ b/src/front/parse.ts
@@ -11,7 +11,7 @@ export function parse(
 export class Parser {
     private toks: Tok[];
     private idx = 0;
-    private currentLine = 1;
+    private currentLoc: Loc = { idx: 0, line: 1, col: 1 };
     private prevTok: Tok | null = null;
 
     constructor(
@@ -148,7 +148,7 @@ export class Parser {
         }
     }
 
-    parseRangeTail(loc: number, begin: ast.Node | null, tok: string): ast.Node {
+    parseRangeTail(loc: Loc, begin: ast.Node | null, tok: string): ast.Node {
         const limit: ast.RangeLimit = tok === ".." ? "Exclusive" : "Inclusive";
         let end: ast.Node | null = null;
         if (![";", ",", ")", "]"].some((tok) => this.test(tok))) {
@@ -319,7 +319,7 @@ export class Parser {
         }
     }
 
-    private mustEat(type: string, loc: number = this.loc()): Tok {
+    private mustEat(type: string, loc = this.loc()): Tok {
         const tok = this.current;
         if (tok.type !== type) {
             this.error(
@@ -333,7 +333,7 @@ export class Parser {
         return tok;
     }
 
-    private error(message: string, loc: number): never {
+    private error(message: string, loc: Loc): never {
         printDiagnostics(this.filename, loc, "error", message, this.text);
         throw new Error();
         Deno.exit(1);
@@ -353,7 +353,7 @@ export class Parser {
         }
         this.idx += 1;
         if (!this.done) {
-            this.currentLine = this.current.line;
+            this.currentLoc = this.current.loc;
         }
     }
 
@@ -361,8 +361,8 @@ export class Parser {
         return !this.done && this.current.type == type;
     }
 
-    private loc(): number {
-        return this.currentLine;
+    private loc(): Loc {
+        return this.currentLoc;
     }
 
     private get current(): Tok {
@@ -374,8 +374,7 @@ export class Parser {
     }
 }
 
-export type Tok = { type: string; value: string; line: number };
-export type Tok2 = { type: string; value: string; loc: Loc };
+export type Tok = { type: string; value: string; loc: Loc };
 
 const keywordPattern =
     /^(?:(?:fn)|(?:return)|(?:let)|(?:if)|(?:else)|(?:while)|(?:break)|(?:or)|(?:and)|(?:not)|(?:mut))/;
@@ -384,13 +383,13 @@ const operatorPattern2 =
     /((?:\->)|(?:==)|(?:!=)|(?:<=)|(?:>=)|(?:<<)|(?:>>)|(?:\.\*)|(?:\.\.)|(?:\.\.=)|[\n\(\)\{\}\[\]\,\.\;\:\!\=\<\>\&\^\|\+\-\*\/\%])/g;
 
 export function tokenize(text: string): Tok[] {
-    return new Lexer<Tok2>()
+    return new Lexer()
         .add(/[ \t\r\n]+/, (_) => null)
         .add(/\/\/[^\n]*/, (_) => null)
         .add(operatorPattern2, (loc, value) => ({ type: value, value, loc }))
         .add(/[a-zA-Z_][a-zA-Z0-9_]*/, (loc, value) => {
             const type = keywordPattern.test(value) ? value : "ident";
-            return ({ type, value, loc });
+            return { type, value, loc };
         })
         .add(/0|(?:[1-9][0-9]*)/, (loc, value) => {
             return { type: "int", value, loc };
@@ -398,21 +397,20 @@ export function tokenize(text: string): Tok[] {
         .add(/./, (loc, value) => {
             return null;
         })
-        .lex(text)
-        .map<Tok>(({ type, value, loc: { line } }) => ({ type, value, line }));
+        .lex(text);
 }
 
-type LexRule<TokT> = {
+type LexRule = {
     pattern: RegExp;
-    action: LexAction<TokT>;
+    action: LexAction;
 };
 
-type LexAction<TokT> = (loc: Loc, match: string) => TokT | null;
+type LexAction = (loc: Loc, match: string) => Tok | null;
 
-class Lexer<TokT> {
-    private rules: LexRule<TokT>[] = [];
+class Lexer {
+    private rules: LexRule[] = [];
 
-    add(pattern: RegExp, action: LexAction<TokT>): this {
+    add(pattern: RegExp, action: LexAction): this {
         this.rules.push({
             pattern: new RegExp(`^(?:${pattern.source})`),
             action,
@@ -420,8 +418,8 @@ class Lexer<TokT> {
         return this;
     }
 
-    lex(text: string): TokT[] {
-        const toks: TokT[] = [];
+    lex(text: string): Tok[] {
+        const toks: Tok[] = [];
         let idx = 0;
         let line = 1;
         let col = 1;
diff --git a/src/front/resolve.ts b/src/front/resolve.ts
index 6ec65e4..4895dd4 100644
--- a/src/front/resolve.ts
+++ b/src/front/resolve.ts
@@ -83,7 +83,7 @@ export function resolve(
                 if (sym === null) {
                     printDiagnostics(
                         filename,
-                        node.line,
+                        node.loc,
                         "error",
                         `undefined symbol '${k.ident}'`,
                         text,