Feb 17, 2025 · Feb 4, 2025 · Feb 6, 2025 · Feb 6, 2025 · Feb 6, 2025 · Feb 17, 2025
diff --git a/packages/eslint-plugin/src/rules/prefer-return-this-type.ts b/packages/eslint-plugin/src/rules/prefer-return-this-type.ts
      }
    }

    function checkProperty(
      node: TSESTree.AccessorProperty | TSESTree.PropertyDefinition,
    ): void {
      if (
        !(
          node.value?.type === AST_NODE_TYPES.FunctionExpression ||
          node.value?.type === AST_NODE_TYPES.ArrowFunctionExpression
        )
      ) {
        return;
      }

      checkFunction(node.value, node.parent.parent);
    }

    return {
      'ClassBody > AccessorProperty': checkProperty,
      'ClassBody > MethodDefinition'(node: TSESTree.MethodDefinition): void {
        checkFunction(node.value, node.parent.parent as ClassLikeDeclaration);
      },
      'ClassBody > PropertyDefinition'(
        node: TSESTree.PropertyDefinition,
      ): void {
        if (
          !(
            node.value?.type === AST_NODE_TYPES.FunctionExpression ||
            node.value?.type === AST_NODE_TYPES.ArrowFunctionExpression
          )
        ) {
          return;
        }

        checkFunction(node.value, node.parent.parent as ClassLikeDeclaration);
        checkFunction(node.value, node.parent.parent);
      },
      'ClassBody > PropertyDefinition': checkProperty,
    };
  },
 });
diff --git a/packages/eslint-plugin/tests/rules/prefer-return-this-type.test.ts b/packages/eslint-plugin/tests/rules/prefer-return-this-type.test.ts
  f(): Base {
    return this;
  }
 }
    `,
    `
 class Foo {
  accessor f = () => {
    return this;
  };
 }
    `,
    `
 class Foo {
  accessor f = (): this => {
    return this;
  };
 }
    `,
    `
 class Foo {
  f?: string;
 }
    `,
  ],
    },
    {
      code: `
 class Foo {
  f = function (): Foo {
    return this;
  };
 }
      `,
      errors: [
        {
          column: 20,
          line: 3,
          messageId: 'useThisType',
        },
      ],
      output: `
 class Foo {
  f = function (): this {
    return this;
  };
 }
      `,
    },
    {
      code: `
 class Foo {
  f(): Foo {
    const self = this;
    },
    {
      code: `
 class Foo {
  accessor f = (): Foo => {
    return this;
  };
 }
      `,
      errors: [
        {
          column: 20,
          line: 3,
          messageId: 'useThisType',
        },
      ],
      output: `
 class Foo {
  accessor f = (): this => {
    return this;
  };
 }
      `,
    },
    {
      code: `
 class Foo {
  accessor f = (): Foo => this;
 }
      `,
      errors: [
        {
          column: 20,
          line: 3,
          messageId: 'useThisType',
        },
      ],
      output: `
 class Foo {
  accessor f = (): this => this;
 }
      `,
    },
    {
      code: `
 class Foo {
  f1(): Foo | undefined {
    return this;
Original file line number	Diff line number	Diff line change
Expand Up		@@ -148,24 +148,27 @@ export default createRule({
		}
		}

		function checkProperty(
		node: TSESTree.AccessorProperty \| TSESTree.PropertyDefinition,
		): void {
		if (
		!(
		node.value?.type === AST_NODE_TYPES.FunctionExpression \|\|
		node.value?.type === AST_NODE_TYPES.ArrowFunctionExpression
		)
		) {
		return;
		}

		checkFunction(node.value, node.parent.parent);
		}

		return {
		'ClassBody > AccessorProperty': checkProperty,
		'ClassBody > MethodDefinition'(node: TSESTree.MethodDefinition): void {
		checkFunction(node.value, node.parent.parent as ClassLikeDeclaration);
		},
		'ClassBody > PropertyDefinition'(
		node: TSESTree.PropertyDefinition,
		): void {
		if (
		!(
		node.value?.type === AST_NODE_TYPES.FunctionExpression \|\|
		node.value?.type === AST_NODE_TYPES.ArrowFunctionExpression
		)
		) {
		return;
		}

		checkFunction(node.value, node.parent.parent as ClassLikeDeclaration);
		checkFunction(node.value, node.parent.parent);
Comment on lines -167 to +169 Copy link MemberAuthor ronamiFeb 6, 2025• edited Loading Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. The type assertion seems unnecessary since#9560. This is an unrelated change, but I decided to include it as it's a tiny change and on the same part of the code that the PR changes anyway. JoshuaKGoldberg reacted with thumbs up emoji Copy link MemberAuthor ronamiFeb 6, 2025• edited Loading Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. I wonder if this can be caught by`no-unnecessary-type-assertion` 🤔 Since`ClassLikeDeclaration` is a different type alias (and thus a different type),the comparison seems to fail (even though`ClassLikeDeclaration` is assigned the same type as the un-asserted type). Inlining the value of the type alias seem to cause`no-unnecessary-type-assertion` to report this. Copy link Member JoshuaKGoldbergFeb 17, 2025 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. Yeah that would be nice. My hunch is it's some nuance about generic functions having type parameters inferred from types of arguments. ronami reacted with thumbs up emoji
		},
		'ClassBody > PropertyDefinition': checkProperty,
		};
		},
		});
Original file line number	Diff line number	Diff line change
Expand Up		@@ -79,6 +79,25 @@ class Derived extends Base {
		f(): Base {
		return this;
		}
		}
		`,
		`
		class Foo {
		accessor f = () => {
		return this;
		};
		}
		`,
		`
		class Foo {
		accessor f = (): this => {
		return this;
		};
		}
		`,
		`
		class Foo {
		f?: string;
		}
		`,
Comment on lines +98 to 102 Copy link MemberAuthor ronamiFeb 6, 2025• edited Loading Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. This is a test addition that isn't related to the`accessor` changes, but was previously uncovered. This fails codecov (as the uncovered code has been moved to a function), and because it's such a tiny addition, I decided to include it in this PR. JoshuaKGoldberg reacted with thumbs up emoji
		],
Expand DownExpand Up		@@ -108,6 +127,29 @@ class Foo {
		},
		{
		code: `
		class Foo {
		f = function (): Foo {
		return this;
		};
		}
		`,
		errors: [
		{
		column: 20,
		line: 3,
		messageId: 'useThisType',
		},
		],
		output: `
		class Foo {
		f = function (): this {
		return this;
		};
		}
		`,
		},
		{
		code: `
		class Foo {
		f(): Foo {
		const self = this;
Expand DownExpand Up		@@ -200,6 +242,48 @@ class Foo {
		},
		{
		code: `
		class Foo {
		accessor f = (): Foo => {
		return this;
		};
		}
		`,
		errors: [
		{
		column: 20,
		line: 3,
		messageId: 'useThisType',
		},
		],
		output: `
		class Foo {
		accessor f = (): this => {
		return this;
		};
		}
		`,
		},
		{
		code: `
		class Foo {
		accessor f = (): Foo => this;
		}
		`,
		errors: [
		{
		column: 20,
		line: 3,
		messageId: 'useThisType',
		},
		],
		output: `
		class Foo {
		accessor f = (): this => this;
		}
		`,
		},
		{
		code: `
		class Foo {
		f1(): Foo \| undefined {
		return this;
Expand Down