fix(ivy): translate WriteKeyExpr expressions properly (#28523)

Translation of WriteKeyExpr expressions was not implemented in the ngtsc
expression translator. This resulted in binding expressions like
"target[key] = $event" not compiling.

This commit fixes the bug by implementing WriteKeyExpr translation.

PR Close #28523

packages/compiler-cli/src/ngtsc/translator/src/translator.ts

@@ -166,8 +166,14 @@ class ExpressionTranslatorVisitor implements ExpressionVisitor, StatementVisitor
     return context.isStatement ? result : ts.createParen(result);
   }
 
-  visitWriteKeyExpr(expr: WriteKeyExpr, context: Context): never {
+  visitWriteKeyExpr(expr: WriteKeyExpr, context: Context): ts.Expression {
-    throw new Error('Method not implemented.');
+    const exprContext = context.withExpressionMode;
+    const lhs = ts.createElementAccess(
+        expr.receiver.visitExpression(this, exprContext),
+        expr.index.visitExpression(this, exprContext), );
+    const rhs = expr.value.visitExpression(this, exprContext);
+    const result: ts.Expression = ts.createBinary(lhs, ts.SyntaxKind.EqualsToken, rhs);
+    return context.isStatement ? result : ts.createParen(result);
   }
 
   visitWritePropExpr(expr: WritePropExpr, context: Context): ts.BinaryExpression {

packages/compiler-cli/test/ngtsc/ngtsc_spec.ts

@@ -863,6 +863,25 @@ describe('ngtsc behavioral tests', () => {
     expect(jsContents).toMatch(contentQueryRegExp('ViewContainerRef', true));
   });
 
+  it('should compile expressions that write keys', () => {
+    env.tsconfig();
+    env.write(`test.ts`, `
+        import {Component, ContentChild, TemplateRef, ViewContainerRef, forwardRef} from '@angular/core';
+
+        @Component({
+          selector: 'test',
+          template: '<div (click)="test[key] = $event">',
+        })
+        class TestCmp {
+          test: any;
+          key: string;
+        }
+    `);
+
+    env.driveMain();
+    expect(env.getContents('test.js')).toContain('test[key] = $event');
+  });
+
   it('should generate host listeners for components', () => {
     env.tsconfig();
     env.write(`test.ts`, `