fix(49478): add return type to method signature (microsoft#49482)

Author: a-tarasyuk

src/services/codefixes/helpers.ts

@@ -332,7 +332,7 @@ namespace ts.codefix {
                     /*questionToken*/ undefined,
                     typeParameters,
                     parameters,
-                    type
+                    type === undefined ? factory.createKeywordTypeNode(SyntaxKind.UnknownKeyword) : type
                 );
             case SyntaxKind.FunctionDeclaration:
                 return factory.createFunctionDeclaration(

src/services/textChanges.ts

@@ -682,7 +682,7 @@ namespace ts.textChanges {
             return {
                 indentation,
                 prefix: (insertLeadingComma ? "," : "") + this.newLineCharacter,
-                suffix: insertTrailingComma ? "," : ""
+                suffix: insertTrailingComma ? "," : isInterfaceDeclaration(node) && isEmpty ? ";" : ""
             };
         }
 

tests/cases/fourslash/codeFixAddMissingMember24.ts

@@ -10,6 +10,6 @@ verify.codeFix({
     index: 0,
     newRangeContent:
 `type Foo = {
-    test(arg0: number, arg1: number, arg2: string);
+    test(arg0: number, arg1: number, arg2: string): unknown;
 };`
 });

tests/cases/fourslash/codeFixAddMissingMember27.ts

@@ -0,0 +1,18 @@
+/// <reference path='fourslash.ts' />
+
+// @noImplicitAny: true
+
+////interface IFoo {}
+////const foo: IFoo = {}
+////foo.bar()
+
+verify.codeFix({
+    description: [ts.Diagnostics.Declare_method_0.message, "bar"],
+    index: 0,
+    newFileContent:
+`interface IFoo {
+    bar(): unknown;
+}
+const foo: IFoo = {}
+foo.bar()`,
+});

tests/cases/fourslash/codeFixAddMissingMember28.ts

@@ -0,0 +1,21 @@
+/// <reference path='fourslash.ts' />
+
+// @noImplicitAny: true
+
+////interface IFoo {
+////    b(): void;
+////}
+////const foo: IFoo = {}
+////foo.a()
+
+verify.codeFix({
+    description: [ts.Diagnostics.Declare_method_0.message, "a"],
+    index: 1,
+    newFileContent:
+`interface IFoo {
+    a(): unknown;
+    b(): void;
+}
+const foo: IFoo = {}
+foo.a()`,
+});

tests/cases/fourslash/codeFixAddMissingMember_all.ts

@@ -72,7 +72,7 @@ En.A;
 type T = {
     x: any;
     y: number;
-    test(arg0: number, arg1: number);
+    test(arg0: number, arg1: number): unknown;
 };
 function foo(t: T) {
     t.x;