Add type infer formatting (microsoft#21850)

* add test for type infer formatting

* Fix type infer formatting

* update test to use condtional

Author: lankaapura

src/services/formatting/rules.ts

@@ -162,6 +162,7 @@ namespace ts.formatting {
                     SyntaxKind.TypeKeyword,
                     SyntaxKind.FromKeyword,
                     SyntaxKind.KeyOfKeyword,
+                    SyntaxKind.InferKeyword,
                 ],
                 anyToken,
                 [isNonJsxSameLineTokenContext],

tests/cases/fourslash/formattingTypeInfer.ts

@@ -0,0 +1,45 @@
+/// <reference path='fourslash.ts'/>
+
+////
+/////*L1*/type C<T> = T extends Array<infer U> ? U : never;
+////
+/////*L2*/  type   C  <  T  >   =   T   extends   Array   <   infer     U  >  ?   U   :   never  ; 
+////
+/////*L3*/type C<T> = T extends Array<infer U> ? U : T;
+////
+/////*L4*/  type   C  <  T  >   =   T   extends   Array   <   infer     U  >  ?   U   :   T  ;  
+////
+/////*L5*/type Foo<T> = T extends { a: infer U, b: infer U } ? U : never;
+////
+/////*L6*/  type   Foo  <  T  > = T   extends   {   a  :   infer   U  ,   b  :   infer   U   }   ?   U   :   never  ;  
+////
+/////*L7*/type Bar<T> = T extends { a: (x: infer U) => void, b: (x: infer U) => void } ? U : never;
+////
+/////*L8*/  type   Bar  <  T  >   =   T   extends   {   a  :   (x  :  infer  U  ) =>   void  ,   b  :   (x  :   infer   U  )   =>   void   }    ?   U   :   never  ;
+////
+
+format.document();
+
+goTo.marker("L1");
+verify.currentLineContentIs("type C<T> = T extends Array<infer U> ? U : never;");
+
+goTo.marker("L2");
+verify.currentLineContentIs("type C<T> = T extends Array<infer U> ? U : never;");
+
+goTo.marker("L3");
+verify.currentLineContentIs("type C<T> = T extends Array<infer U> ? U : T;");
+
+goTo.marker("L4");
+verify.currentLineContentIs("type C<T> = T extends Array<infer U> ? U : T;");
+
+goTo.marker("L5");
+verify.currentLineContentIs("type Foo<T> = T extends { a: infer U, b: infer U } ? U : never;");
+
+goTo.marker("L6");
+verify.currentLineContentIs("type Foo<T> = T extends { a: infer U, b: infer U } ? U : never;");
+
+goTo.marker("L7");
+verify.currentLineContentIs("type Bar<T> = T extends { a: (x: infer U) => void, b: (x: infer U) => void } ? U : never;");
+
+goTo.marker("L8");
+verify.currentLineContentIs("type Bar<T> = T extends { a: (x: infer U) => void, b: (x: infer U) => void } ? U : never;");