Partially implemented typechecking for calls

src/typechecker/TypeChecker.ts

@@ -36,6 +36,8 @@ import AnyType from "./AnyType";
 import TypeExpr, { TypeExprVisitor, VariableTypeExpr } from "../TypeExpr";
 import { zip } from "../helpers";
 import CallableType from "./CallableType";
+import { type } from "os";
+import { cachedDataVersionTag } from "v8";
 
 class LoxError {
     constructor(
@@ -390,9 +392,23 @@ implements ExprVisitor<Type>, StmtVisitor<void>, TypeExprVisitor<Type> {
     }
 
     visitCallExpr(expr: CallExpr): Type {
-        throw "Not Implemented Yet";
-        // this.resolve(expr.callee);
-        // this.resolveAll(expr.args);
+        const calleeType = this.checkExpr(expr.callee);
+
+        if (calleeType.tag !== "CALLABLE") {
+            if (calleeType !== types.PreviousTypeError) {
+                this.error(`Type '${calleeType}' is not callable.`);
+            }
+            for (const arg of expr.args) {
+                this.checkExpr(arg);
+            }
+            return types.PreviousTypeError;
+        }
+
+        // TODO check arity
+        // TODO check params
+
+        return calleeType.returns ?? types.Nil;
+
     }
 
     visitGetExpr(expr: GetExpr): Type {

tests/functions/callPreviousTypeError.lox

@@ -0,0 +1,7 @@
+// Because the callee is not defined, we cannot infer the type of
+// func. This means the subsequent call cannot be meaningfully checked,
+// so it should not show any errors.
+var func = notDefined();
+func(1, 2, 3);
+-- ERROR --
+[line 4] Error at 'notDefined': The name 'notDefined' is not defined.

tests/functions/callUncallable.lox

@@ -0,0 +1,4 @@
+var x = "hello";
+x();
+-- ERROR --
+[line 0] Error: Type 'String' is not callable.

tests/functions/callUndefined.lox

@@ -0,0 +1,6 @@
+// The typechecker should only complain about foo being undefined, and
+// not further complain that it isn't callable or that the parameter types
+// are incorrect.
+foo(1, 2, 3);
+-- ERROR --
+[line 4] Error at 'foo': The name 'foo' is not defined.

tests/functions/closure.lox

@@ -1,6 +1,6 @@
-fun makeCounter(): Number {
+fun makeCounter(): fun(): Number {
   var i = 0;
-  fun count() {
+  fun count(): Number {
     i = i + 1;
     return i;
   }

tests/functions/fibonacci.lox

@@ -2,7 +2,6 @@ fun fibonacci(n: Number): Number {
   if (n <= 1) return n;
   return fibonacci(n - 2) + fibonacci(n - 1);
 }
-
 for (var i = 0; i < 6; i = i + 1) {
   print fibonacci(i);
 }