From 1937257e1f048c446dfeafd4b356bcbc9a13e964 Mon Sep 17 00:00:00 2001
From: Ronen Amiel <ronen.amiel@gmail.com>
Date: Sat, 7 Dec 2024 20:48:25 +0200
Subject: [PATCH 1/2] [no-unnecessary-boolean-literal-compare] lag values of a
 type parameter with boolean type constraints

---
 .../no-unnecessary-boolean-literal-compare.ts | 12 ++-
 ...nnecessary-boolean-literal-compare.test.ts | 87 +++++++++++++++++++
 2 files changed, 97 insertions(+), 2 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/no-unnecessary-boolean-literal-compare.ts b/packages/eslint-plugin/src/rules/no-unnecessary-boolean-literal-compare.ts
index 9a0c38c47a80..db96ef6f2a8f 100644
--- a/packages/eslint-plugin/src/rules/no-unnecessary-boolean-literal-compare.ts
+++ b/packages/eslint-plugin/src/rules/no-unnecessary-boolean-literal-compare.ts
@@ -4,7 +4,12 @@ import { AST_NODE_TYPES } from '@typescript-eslint/utils';
 import * as tsutils from 'ts-api-utils';
 import * as ts from 'typescript';
 
-import { createRule, getParserServices, isStrongPrecedenceNode } from '../util';
+import {
+  createRule,
+  getConstrainedTypeAtLocation,
+  getParserServices,
+  isStrongPrecedenceNode,
+} from '../util';
 
 type MessageIds =
   | 'comparingNullableToFalse'
@@ -89,7 +94,10 @@ export default createRule<Options, MessageIds>({
         return undefined;
       }
 
-      const expressionType = services.getTypeAtLocation(comparison.expression);
+      const expressionType = getConstrainedTypeAtLocation(
+        services,
+        comparison.expression,
+      );
 
       if (isBooleanType(expressionType)) {
         return {
diff --git a/packages/eslint-plugin/tests/rules/no-unnecessary-boolean-literal-compare.test.ts b/packages/eslint-plugin/tests/rules/no-unnecessary-boolean-literal-compare.test.ts
index 331212829ca3..a7f4724322d6 100644
--- a/packages/eslint-plugin/tests/rules/no-unnecessary-boolean-literal-compare.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unnecessary-boolean-literal-compare.test.ts
@@ -55,6 +55,18 @@ ruleTester.run('no-unnecessary-boolean-literal-compare', rule, {
       declare const varTrueOrStringOrUndefined: true | string | undefined;
       varTrueOrStringOrUndefined == true;
     `,
+    `
+      const test: <T>(someCondition: T) => void = someCondition => {
+        if (someCondition === true) {
+        }
+      };
+    `,
+    `
+      const test: <T>(someCondition: boolean | string) => void = someCondition => {
+        if (someCondition === true) {
+        }
+      };
+    `,
     `
       declare const varBooleanOrUndefined: boolean | undefined;
       varBooleanOrUndefined === true;
@@ -73,6 +85,24 @@ ruleTester.run('no-unnecessary-boolean-literal-compare', rule, {
       `,
       options: [{ allowComparingNullableBooleansToTrue: false }],
     },
+    {
+      code: `
+        const test: <T>(someCondition: boolean | undefined) => void = someCondition => {
+          if (someCondition === true) {
+          }
+        };
+      `,
+      options: [{ allowComparingNullableBooleansToFalse: false }],
+    },
+    {
+      code: `
+        const test: <T>(someCondition: boolean | undefined) => void = someCondition => {
+          if (someCondition === false) {
+          }
+        };
+      `,
+      options: [{ allowComparingNullableBooleansToTrue: false }],
+    },
     "'false' === true;",
     "'true' === false;",
   ],
@@ -481,5 +511,62 @@ ruleTester.run('no-unnecessary-boolean-literal-compare', rule, {
         }
       `,
     },
+    {
+      code: `
+        const test: <T extends boolean>(someCondition: T) => void = someCondition => {
+          if (someCondition === true) {
+          }
+        };
+      `,
+      errors: [
+        {
+          messageId: 'direct',
+        },
+      ],
+      output: `
+        const test: <T extends boolean>(someCondition: T) => void = someCondition => {
+          if (someCondition) {
+          }
+        };
+      `,
+    },
+    {
+      code: `
+        const test: <T extends boolean>(someCondition: T) => void = someCondition => {
+          if (!(someCondition !== false)) {
+          }
+        };
+      `,
+      errors: [
+        {
+          messageId: 'negated',
+        },
+      ],
+      output: `
+        const test: <T extends boolean>(someCondition: T) => void = someCondition => {
+          if (!someCondition) {
+          }
+        };
+      `,
+    },
+    {
+      code: `
+        const test: <T extends boolean>(someCondition: T) => void = someCondition => {
+          if (!((someCondition ?? true) !== false)) {
+          }
+        };
+      `,
+      errors: [
+        {
+          messageId: 'negated',
+        },
+      ],
+      output: `
+        const test: <T extends boolean>(someCondition: T) => void = someCondition => {
+          if (!(someCondition ?? true)) {
+          }
+        };
+      `,
+    },
   ],
 });

From 60e677a180fa3ea849d71a1825ec396780585038 Mon Sep 17 00:00:00 2001
From: Ronen Amiel <ronen.amiel@gmail.com>
Date: Sat, 14 Dec 2024 09:57:02 +0200
Subject: [PATCH 2/2] fix redundant tests

---
 .../rules/no-unnecessary-boolean-literal-compare.test.ts  | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/packages/eslint-plugin/tests/rules/no-unnecessary-boolean-literal-compare.test.ts b/packages/eslint-plugin/tests/rules/no-unnecessary-boolean-literal-compare.test.ts
index a7f4724322d6..f99a78ff9df6 100644
--- a/packages/eslint-plugin/tests/rules/no-unnecessary-boolean-literal-compare.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unnecessary-boolean-literal-compare.test.ts
@@ -87,7 +87,9 @@ ruleTester.run('no-unnecessary-boolean-literal-compare', rule, {
     },
     {
       code: `
-        const test: <T>(someCondition: boolean | undefined) => void = someCondition => {
+        const test: <T extends boolean | undefined>(
+          someCondition: T,
+        ) => void = someCondition => {
           if (someCondition === true) {
           }
         };
@@ -96,7 +98,9 @@ ruleTester.run('no-unnecessary-boolean-literal-compare', rule, {
     },
     {
       code: `
-        const test: <T>(someCondition: boolean | undefined) => void = someCondition => {
+        const test: <T extends boolean | undefined>(
+          someCondition: T,
+        ) => void = someCondition => {
           if (someCondition === false) {
           }
         };

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