From f611faadfedd8dc2c3291da98e2c2c60fe3984bd Mon Sep 17 00:00:00 2001
From: Kristiyan Kostadinov <crisbeto@abv.bg>
Date: Tue, 17 Sep 2024 09:46:35 +0200
Subject: [PATCH] fix(compiler-cli): extended diagnostics not validating ICUs
 (#57845)

The visitor that all extended diagnostics are based on hadn't implemented the `visitIcu` method which meant that it wasn't detecting any code inside of them.

Fixes #57838.

PR Close #57845
---
 .../compiler-cli/src/ngtsc/typecheck/extended/api/api.ts | 5 ++++-
 .../unused_let_declaration_spec.ts                       | 9 +++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/packages/compiler-cli/src/ngtsc/typecheck/extended/api/api.ts b/packages/compiler-cli/src/ngtsc/typecheck/extended/api/api.ts
index 31149c33846ed..3c27bb3adcb45 100644
--- a/packages/compiler-cli/src/ngtsc/typecheck/extended/api/api.ts
+++ b/packages/compiler-cli/src/ngtsc/typecheck/extended/api/api.ts
@@ -228,7 +228,10 @@ class TemplateVisitor<Code extends ErrorCode>
   visitBoundText(text: TmplAstBoundText): void {
     this.visitAst(text.value);
   }
-  visitIcu(icu: TmplAstIcu): void {}
+  visitIcu(icu: TmplAstIcu): void {
+    Object.keys(icu.vars).forEach((key) => this.visit(icu.vars[key]));
+    Object.keys(icu.placeholders).forEach((key) => this.visit(icu.placeholders[key]));
+  }
 
   visitDeferredBlock(deferred: TmplAstDeferredBlock): void {
     deferred.visitAll(this);
diff --git a/packages/compiler-cli/src/ngtsc/typecheck/extended/test/checks/unused_let_declaration/unused_let_declaration_spec.ts b/packages/compiler-cli/src/ngtsc/typecheck/extended/test/checks/unused_let_declaration/unused_let_declaration_spec.ts
index 3afced6bf38a9..209945e915ddc 100644
--- a/packages/compiler-cli/src/ngtsc/typecheck/extended/test/checks/unused_let_declaration/unused_let_declaration_spec.ts
+++ b/packages/compiler-cli/src/ngtsc/typecheck/extended/test/checks/unused_let_declaration/unused_let_declaration_spec.ts
@@ -108,5 +108,14 @@ runInEachFileSystem(() => {
 
       expect(diags.length).toBe(0);
     });
+
+    it('should not report a @let declaration that is only used in an ICU', () => {
+      const diags = diagnose(`
+        @let value = 1;
+        <h1 i18n>{value, select, 1 {one} 2 {two} other {other}}</h1>
+      `);
+
+      expect(diags.length).toBe(0);
+    });
   });
 });