From 7236104b3c8db50591ef225d6e2028fdbf9f82e0 Mon Sep 17 00:00:00 2001
From: Joshua Chen <sidachen2003@gmail.com>
Date: Wed, 13 Jul 2022 11:51:07 +0800
Subject: [PATCH 1/2] fix(eslint-plugin): [no-inferrable] fix optional param to
 valid code

---
 .../src/rules/no-inferrable-types.ts          | 12 ++++++++++-
 .../tests/rules/no-inferrable-types.test.ts   | 21 ++++++++++++++++++-
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/no-inferrable-types.ts b/packages/eslint-plugin/src/rules/no-inferrable-types.ts
index 9adb4bca9ecd..e32c1d065b2b 100644
--- a/packages/eslint-plugin/src/rules/no-inferrable-types.ts
+++ b/packages/eslint-plugin/src/rules/no-inferrable-types.ts
@@ -46,6 +46,8 @@ export default util.createRule<Options, MessageIds>({
     },
   ],
   create(context, [{ ignoreParameters, ignoreProperties }]) {
+    const sourceCode = context.getSourceCode();
+
     function isFunctionCall(
       init: TSESTree.Expression,
       callName: string,
@@ -215,7 +217,15 @@ export default util.createRule<Options, MessageIds>({
         data: {
           type,
         },
-        fix: fixer => fixer.remove(typeNode),
+        *fix(fixer) {
+          if (
+            node.type === AST_NODE_TYPES.AssignmentPattern &&
+            node.left.optional
+          ) {
+            yield fixer.remove(sourceCode.getTokenBefore(typeNode)!);
+          }
+          yield fixer.remove(typeNode);
+        },
       });
     }
 
diff --git a/packages/eslint-plugin/tests/rules/no-inferrable-types.test.ts b/packages/eslint-plugin/tests/rules/no-inferrable-types.test.ts
index d85806b69c4e..7f06a27c0da7 100644
--- a/packages/eslint-plugin/tests/rules/no-inferrable-types.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-inferrable-types.test.ts
@@ -156,7 +156,26 @@ class Foo {
 
   invalid: [
     ...invalidTestCases,
-
+    {
+      // This is invalid TS semantic, but it's trivial to make valid anyway
+      code: 'const fn = (a?: number = 5) => {};',
+      output: 'const fn = (a = 5) => {};',
+      options: [
+        {
+          ignoreParameters: false,
+        },
+      ],
+      errors: [
+        {
+          messageId: 'noInferrableType',
+          data: {
+            type: 'number',
+          },
+          line: 1,
+          column: 13,
+        },
+      ],
+    },
     {
       code: "const fn = (a: number = 5, b: boolean = true, c: string = 'foo') => {};",
       output: "const fn = (a = 5, b = true, c = 'foo') => {};",

From 7598abb9f13dc9fabebdd267f7bda2b0519f0e2d Mon Sep 17 00:00:00 2001
From: Joshua Chen <sidachen2003@gmail.com>
Date: Thu, 14 Jul 2022 11:43:22 +0800
Subject: [PATCH 2/2] Add definite assignment

---
 .../src/rules/no-inferrable-types.ts          |  5 ++--
 .../tests/rules/no-inferrable-types.test.ts   | 28 +++++++++++++++++++
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/no-inferrable-types.ts b/packages/eslint-plugin/src/rules/no-inferrable-types.ts
index e32c1d065b2b..e77b694cc707 100644
--- a/packages/eslint-plugin/src/rules/no-inferrable-types.ts
+++ b/packages/eslint-plugin/src/rules/no-inferrable-types.ts
@@ -219,8 +219,9 @@ export default util.createRule<Options, MessageIds>({
         },
         *fix(fixer) {
           if (
-            node.type === AST_NODE_TYPES.AssignmentPattern &&
-            node.left.optional
+            (node.type === AST_NODE_TYPES.AssignmentPattern &&
+              node.left.optional) ||
+            (node.type === AST_NODE_TYPES.PropertyDefinition && node.definite)
           ) {
             yield fixer.remove(sourceCode.getTokenBefore(typeNode)!);
           }
diff --git a/packages/eslint-plugin/tests/rules/no-inferrable-types.test.ts b/packages/eslint-plugin/tests/rules/no-inferrable-types.test.ts
index 7f06a27c0da7..cfea578b9f61 100644
--- a/packages/eslint-plugin/tests/rules/no-inferrable-types.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-inferrable-types.test.ts
@@ -176,6 +176,34 @@ class Foo {
         },
       ],
     },
+    {
+      // This is invalid TS semantic, but it's trivial to make valid anyway
+      code: `
+class A {
+  a!: number = 1;
+}
+      `,
+      output: `
+class A {
+  a = 1;
+}
+      `,
+      options: [
+        {
+          ignoreProperties: false,
+        },
+      ],
+      errors: [
+        {
+          messageId: 'noInferrableType',
+          data: {
+            type: 'number',
+          },
+          line: 3,
+          column: 3,
+        },
+      ],
+    },
     {
       code: "const fn = (a: number = 5, b: boolean = true, c: string = 'foo') => {};",
       output: "const fn = (a = 5, b = true, c = 'foo') => {};",