Fix bug in typechecker for array assignment

Author: bryanlohxz

src/ast/astExtractor/statement-extractor.ts

@@ -39,6 +39,7 @@ import {
   ExpressionStatement,
   IfStatement,
   MethodInvocation,
+  Primary,
   Statement,
   StatementExpression,
   VariableDeclarator,
@@ -158,10 +159,26 @@ export class StatementExtractor extends BaseJavaCstVisitorWithDefaults {
     return this.visit(ctx.primary);
   }
 
-  primary(ctx: PrimaryCtx) {
+  primary(ctx: PrimaryCtx): Primary {
     // Assignment LHS, MethodInvocation identifier
     let { name, location } = this.visit(ctx.primaryPrefix);
     if (ctx.primarySuffix) {
+      const lastSuffix = ctx.primarySuffix[ctx.primarySuffix.length - 1];
+      if (lastSuffix.children.arrayAccessSuffix) {
+        const expressionExtractor = new ExpressionExtractor();
+        const newPrimaryCtx: PrimaryCtx = { primaryPrefix: ctx.primaryPrefix };
+        if (ctx.primarySuffix.length - 1 > 0) {
+          const newSuffixArray = ctx.primarySuffix.filter(
+            (_, index) => index !== ctx.primarySuffix!.length - 1
+          );
+          newPrimaryCtx.primarySuffix = newSuffixArray;
+        }
+        return {
+          ...expressionExtractor.visit(lastSuffix.children.arrayAccessSuffix),
+          primary: this.primary(newPrimaryCtx) as Primary,
+        };
+      }
+
       for (const s of ctx.primarySuffix.filter(
         (s) => !s.children.methodInvocationSuffix
       )) {

src/types/checker/__tests__/arrays.test.ts

@@ -65,7 +65,6 @@ const testcases: {
       numbers[0] = 10; // Correct assignment
     `,
     result: { type: null, errors: [] },
-    only: true,
   },
   {
     input: `

src/types/checker/index.ts

@@ -1,12 +1,10 @@
-import {
-  ExpressionName,
-  VariableInitializer,
-} from "../../ast/types/blocks-and-statements";
+import { Array as ArrayType } from "../types/arrays";
 import { Frame } from "./environment";
+import { Integer, String } from "../types/nonPrimitives";
 import { Method } from "../types/methods";
 import { Node } from "../../ast/types/ast";
-import { Integer, String } from "../types/nonPrimitives";
 import { Type } from "../types/type";
+import { VariableInitializer } from "../../ast/types/blocks-and-statements";
 import {
   ArrayRequiredError,
   BadOperandTypesError,
@@ -29,7 +27,6 @@ import {
   getFloatType,
   getNumberType,
 } from "../types/primitives";
-import { Array as ArrayType } from "../types/arrays";
 
 export type Result = {
   currentType: Type | null;
@@ -71,9 +68,12 @@ export const check = (
       return newResult(primaryCheck.currentType.getContentType());
     }
     case "Assignment": {
-      const left = node.left as ExpressionName;
+      const leftCheck = check(node.left, frame);
+      if (leftCheck.errors.length > 0) return newResult(null, leftCheck.errors);
+      if (!leftCheck.currentType)
+        throw new Error("Left type in assignment should exist.");
       const right = node.right;
-      const leftType = frame.getVariable(left.name);
+      const leftType = leftCheck.currentType;
       if (leftType instanceof Error) return newResult(null, [leftType]);
       const { currentType, errors } = check(right, frame);
       if (errors.length > 0) return newResult(null, errors);