Feb 12, 2022 · Feb 12, 2022 · Feb 12, 2022
diff --git a/packages/eslint-plugin/src/rules/no-unnecessary-type-arguments.ts b/packages/eslint-plugin/src/rules/no-unnecessary-type-arguments.ts
  create(context) {
    const parserServices = util.getParserServices(context);
    const checker = parserServices.program.getTypeChecker();
    const sourceCode = context.getSourceCode();

    function checkTSArgsAndParameters(
      esParameters: TSESTree.TSTypeParameterInstantiation,
      const i = esParameters.params.length - 1;
      const arg = esParameters.params[i];
      const param = typeParameters[i];

      if (!param?.default) {
        return;
      }
      // TODO: would like checker.areTypesEquivalent. https://github.com/Microsoft/TypeScript/issues/13502
      if (
        !param?.default ||
        param.default.getText() !== sourceCode.getText(arg)
      const defaultType = checker.getTypeAtLocation(param.default);
      const argTsNode = parserServices.esTreeNodeToTSNodeMap.get(arg);
      const argType = checker.getTypeAtLocation(argTsNode);
      if (!argType.aliasSymbol && !defaultType.aliasSymbol) {
        if (argType.flags !== defaultType.flags) {
          return;
        }
      } else if (
        argType.aliasSymbol !== defaultType.aliasSymbol ||
        argType.aliasTypeArguments !== defaultType.aliasTypeArguments
      ) {
        return;
      }
diff --git a/packages/eslint-plugin/tests/rules/no-unnecessary-type-arguments.test.ts b/packages/eslint-plugin/tests/rules/no-unnecessary-type-arguments.test.ts
 bar();
      `,
    },
    {
      code: `
 type DefaultE = { foo: string };
 type T<E = DefaultE> = { box: E };
 type G = T<DefaultE>;
 declare module 'bar' {
  type DefaultE = { somethingElse: true };
  type G = T<DefaultE>;
 }
      `,
      errors: [
        {
          line: 4,
          column: 12,
          messageId: 'unnecessaryTypeParameter',
        },
      ],
      output: `
 type DefaultE = { foo: string };
 type T<E = DefaultE> = { box: E };
 type G = T;
 declare module 'bar' {
  type DefaultE = { somethingElse: true };
  type G = T<DefaultE>;
 }
      `,
    },
  ],
 });
Original file line number	Diff line number	Diff line change
Expand Up		@@ -37,7 +37,6 @@ export default util.createRule<[], MessageIds>({
		create(context) {
		const parserServices = util.getParserServices(context);
		const checker = parserServices.program.getTypeChecker();
		const sourceCode = context.getSourceCode();

		function checkTSArgsAndParameters(
		esParameters: TSESTree.TSTypeParameterInstantiation,
Expand All		@@ -47,11 +46,20 @@ export default util.createRule<[], MessageIds>({
		const i = esParameters.params.length - 1;
		const arg = esParameters.params[i];
		const param = typeParameters[i];

		if (!param?.default) {
		return;
		}
		// TODO: would like checker.areTypesEquivalent. https://github.com/Microsoft/TypeScript/issues/13502
		if (
		!param?.default \|\|
		param.default.getText() !== sourceCode.getText(arg)
		const defaultType = checker.getTypeAtLocation(param.default);
		const argTsNode = parserServices.esTreeNodeToTSNodeMap.get(arg);
		const argType = checker.getTypeAtLocation(argTsNode);
		if (!argType.aliasSymbol && !defaultType.aliasSymbol) {
		if (argType.flags !== defaultType.flags) {
		return;
		}
		} else if (
		argType.aliasSymbol !== defaultType.aliasSymbol \|\|
		argType.aliasTypeArguments !== defaultType.aliasTypeArguments
		) {
		return;
		}
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -290,5 +290,32 @@ function bar<T = F<string>>() {}
		bar();
		`,
		},
		{
		code: `
		type DefaultE = { foo: string };
		type T<E = DefaultE> = { box: E };
		type G = T<DefaultE>;
		declare module 'bar' {
		type DefaultE = { somethingElse: true };
		type G = T<DefaultE>;
		}
		`,
		errors: [
		{
		line: 4,
		column: 12,
		messageId: 'unnecessaryTypeParameter',
		},
		],
		output: `
		type DefaultE = { foo: string };
		type T<E = DefaultE> = { box: E };
		type G = T;
		declare module 'bar' {
		type DefaultE = { somethingElse: true };
		type G = T<DefaultE>;
		}
		`,
		},
		],
		});