Fix build in the presence of definite assignment analysis (#20170)

Author: weswigham

tests/baselines/reference/narrowingConstrainedTypeVariable.js

@@ -23,7 +23,7 @@ function f2<T extends C, U extends D>(v: T | U) {
     }
 }
 
-class E { x: string }
+class E { x: string | undefined }
 
 function f3<T extends E>(v: T | { x: string }) {
     if (v instanceof E) {

tests/baselines/reference/narrowingConstrainedTypeVariable.symbols

@@ -57,12 +57,12 @@ function f2<T extends C, U extends D>(v: T | U) {
     }
 }
 
-class E { x: string }
+class E { x: string | undefined }
 >E : Symbol(E, Decl(narrowingConstrainedTypeVariable.ts, 22, 1))
 >x : Symbol(E.x, Decl(narrowingConstrainedTypeVariable.ts, 24, 9))
 
 function f3<T extends E>(v: T | { x: string }) {
->f3 : Symbol(f3, Decl(narrowingConstrainedTypeVariable.ts, 24, 21))
+>f3 : Symbol(f3, Decl(narrowingConstrainedTypeVariable.ts, 24, 33))
 >T : Symbol(T, Decl(narrowingConstrainedTypeVariable.ts, 26, 12))
 >E : Symbol(E, Decl(narrowingConstrainedTypeVariable.ts, 22, 1))
 >v : Symbol(v, Decl(narrowingConstrainedTypeVariable.ts, 26, 25))

tests/baselines/reference/narrowingConstrainedTypeVariable.types

@@ -59,9 +59,9 @@ function f2<T extends C, U extends D>(v: T | U) {
     }
 }
 
-class E { x: string }
+class E { x: string | undefined }
 >E : E
->x : string
+>x : string | undefined
 
 function f3<T extends E>(v: T | { x: string }) {
 >f3 : <T extends E>(v: T | { x: string; }) => void

tests/cases/conformance/types/typeRelationships/instanceOf/narrowingConstrainedTypeVariable.ts

@@ -24,7 +24,7 @@ function f2<T extends C, U extends D>(v: T | U) {
     }
 }
 
-class E { x: string }
+class E { x: string | undefined }
 
 function f3<T extends E>(v: T | { x: string }) {
     if (v instanceof E) {