From f502178d5c7ba94005a9f5b852a6d56ce02ae39c Mon Sep 17 00:00:00 2001
From: Kirk Waiblinger <53019676+kirkwaiblinger@users.noreply.github.com>
Date: Fri, 12 Sep 2025 15:13:18 -0600
Subject: [PATCH 1/2] fix(eslint-plugin): [no-unsafe-enum-comparison] support
 unions of literals

---
 .../src/rules/no-unsafe-enum-comparison.ts    | 36 +++++----
 .../rules/no-unsafe-enum-comparison.test.ts   | 76 +++++++++++++++++++
 2 files changed, 98 insertions(+), 14 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/no-unsafe-enum-comparison.ts b/packages/eslint-plugin/src/rules/no-unsafe-enum-comparison.ts
index c5f457db3618..051a827ee720 100644
--- a/packages/eslint-plugin/src/rules/no-unsafe-enum-comparison.ts
+++ b/packages/eslint-plugin/src/rules/no-unsafe-enum-comparison.ts
@@ -23,25 +23,33 @@ function typeViolates(leftTypeParts: ts.Type[], rightType: ts.Type): boolean {
 }
 
 function isNumberLike(type: ts.Type): boolean {
-  const typeParts = tsutils.intersectionConstituents(type);
-
-  return typeParts.some(typePart => {
-    return tsutils.isTypeFlagSet(
-      typePart,
-      ts.TypeFlags.Number | ts.TypeFlags.NumberLike,
+  return tsutils
+    .unionConstituents(type)
+    .every(unionPart =>
+      tsutils
+        .intersectionConstituents(unionPart)
+        .some(intersectionPart =>
+          tsutils.isTypeFlagSet(
+            intersectionPart,
+            ts.TypeFlags.Number | ts.TypeFlags.NumberLike,
+          ),
+        ),
     );
-  });
 }
 
 function isStringLike(type: ts.Type): boolean {
-  const typeParts = tsutils.intersectionConstituents(type);
-
-  return typeParts.some(typePart => {
-    return tsutils.isTypeFlagSet(
-      typePart,
-      ts.TypeFlags.String | ts.TypeFlags.StringLike,
+  return tsutils
+    .unionConstituents(type)
+    .every(unionPart =>
+      tsutils
+        .intersectionConstituents(unionPart)
+        .some(intersectionPart =>
+          tsutils.isTypeFlagSet(
+            intersectionPart,
+            ts.TypeFlags.String | ts.TypeFlags.StringLike,
+          ),
+        ),
     );
-  });
 }
 
 /**
diff --git a/packages/eslint-plugin/tests/rules/no-unsafe-enum-comparison.test.ts b/packages/eslint-plugin/tests/rules/no-unsafe-enum-comparison.test.ts
index 89e28f163314..605ed0113ece 100644
--- a/packages/eslint-plugin/tests/rules/no-unsafe-enum-comparison.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unsafe-enum-comparison.test.ts
@@ -1165,5 +1165,81 @@ ruleTester.run('no-unsafe-enum-comparison', rule, {
       `,
       errors: [{ messageId: 'mismatchedCondition' }],
     },
+    {
+      code: `
+enum NUMBER_ENUM {
+  First = 0,
+  Second = 1,
+}
+
+type NumberUnion = 0 | 1;
+
+declare const numberUnion: NumberUnion;
+
+switch (numberUnion) {
+  case NUMBER_ENUM.First:
+  case NUMBER_ENUM.Second:
+    break;
+}
+      `,
+      errors: [
+        {
+          messageId: 'mismatchedCase',
+          line: 12,
+        },
+        {
+          messageId: 'mismatchedCase',
+          line: 13,
+        },
+      ],
+    },
+    {
+      code: `
+enum STRING_ENUM {
+  First = 'one',
+  Second = 'two',
+}
+
+type StringUnion = 'one' | 'two';
+
+declare const stringUnion: StringUnion;
+
+switch (stringUnion) {
+  case STRING_ENUM.First:
+  case STRING_ENUM.Second:
+    break;
+}
+      `,
+      errors: [
+        {
+          messageId: 'mismatchedCase',
+          line: 12,
+        },
+        {
+          messageId: 'mismatchedCase',
+          line: 13,
+        },
+      ],
+    },
+    {
+      code: `
+declare const stringUnion: 'foo' | 'bar';
+
+enum StringEnum {
+  FOO = 'foo',
+  BAR = 'bar',
+}
+
+declare const stringEnum: StringEnum;
+
+stringUnion === stringEnum;
+      `,
+      errors: [
+        {
+          messageId: 'mismatchedCondition',
+          line: 11,
+        },
+      ],
+    },
   ],
 });

From e74b701db026a3379adbfb000566ceb433493ef1 Mon Sep 17 00:00:00 2001
From: Kirk Waiblinger <53019676+kirkwaiblinger@users.noreply.github.com>
Date: Fri, 12 Sep 2025 15:48:39 -0600
Subject: [PATCH 2/2] lint fix

---
 .../tests/rules/no-unsafe-enum-comparison.test.ts      | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/packages/eslint-plugin/tests/rules/no-unsafe-enum-comparison.test.ts b/packages/eslint-plugin/tests/rules/no-unsafe-enum-comparison.test.ts
index 605ed0113ece..b10f3cc6ee5f 100644
--- a/packages/eslint-plugin/tests/rules/no-unsafe-enum-comparison.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unsafe-enum-comparison.test.ts
@@ -1184,12 +1184,12 @@ switch (numberUnion) {
       `,
       errors: [
         {
-          messageId: 'mismatchedCase',
           line: 12,
+          messageId: 'mismatchedCase',
         },
         {
-          messageId: 'mismatchedCase',
           line: 13,
+          messageId: 'mismatchedCase',
         },
       ],
     },
@@ -1212,12 +1212,12 @@ switch (stringUnion) {
       `,
       errors: [
         {
-          messageId: 'mismatchedCase',
           line: 12,
+          messageId: 'mismatchedCase',
         },
         {
-          messageId: 'mismatchedCase',
           line: 13,
+          messageId: 'mismatchedCase',
         },
       ],
     },
@@ -1236,8 +1236,8 @@ stringUnion === stringEnum;
       `,
       errors: [
         {
-          messageId: 'mismatchedCondition',
           line: 11,
+          messageId: 'mismatchedCondition',
         },
       ],
     },