Cherry-pick PR #50497 into release-4.8 (#50590)

Component commits:
40a5fc1 Handle intersections in isGenericTypeWithoutNullableConstraint

7a14338 Add regression test

Co-authored-by: Anders Hejlsberg <andersh@microsoft.com>

Author: TypeScript Bot

src/compiler/checker.ts

@@ -25756,8 +25756,10 @@ namespace ts {
                 !!(type.flags & TypeFlags.Instantiable && getBaseConstraintOrType(type).flags & (TypeFlags.Nullable | TypeFlags.Union));
         }
 
-        function isGenericTypeWithoutNullableConstraint(type: Type) {
-            return !!(type.flags & TypeFlags.Instantiable && !maybeTypeOfKind(getBaseConstraintOrType(type), TypeFlags.Nullable));
+        function isGenericTypeWithoutNullableConstraint(type: Type): boolean {
+            return type.flags & TypeFlags.Intersection ?
+                some((type as IntersectionType).types, isGenericTypeWithoutNullableConstraint) :
+                !!(type.flags & TypeFlags.Instantiable && !maybeTypeOfKind(getBaseConstraintOrType(type), TypeFlags.Nullable));
         }
 
         function hasContextualTypeWithNoGenericTypes(node: Node, checkMode: CheckMode | undefined) {

tests/baselines/reference/controlFlowGenericTypes.errors.txt

@@ -240,4 +240,12 @@ tests/cases/conformance/controlFlow/controlFlowGenericTypes.ts(168,9): error TS2
             control[key] = value;
         }
     }
+    
+    // Repro from #50465
+    
+    type Column<T> = (keyof T extends never ? { id?: number | string } : { id: T }) & { title?: string; }
+    
+    function getColumnProperty<T>(column: Column<T>, key: keyof Column<T>) {
+      return column[key];
+    }
 

tests/baselines/reference/controlFlowGenericTypes.js

@@ -210,6 +210,14 @@ function update<T extends Control, K extends keyof T>(control : T | undefined, k
         control[key] = value;
     }
 }
+
+// Repro from #50465
+
+type Column<T> = (keyof T extends never ? { id?: number | string } : { id: T }) & { title?: string; }
+
+function getColumnProperty<T>(column: Column<T>, key: keyof Column<T>) {
+  return column[key];
+}
 
 
 //// [controlFlowGenericTypes.js]
@@ -368,3 +376,6 @@ function update(control, key, value) {
         control[key] = value;
     }
 }
+function getColumnProperty(column, key) {
+    return column[key];
+}

tests/baselines/reference/controlFlowGenericTypes.symbols

@@ -626,3 +626,29 @@ function update<T extends Control, K extends keyof T>(control : T | undefined, k
     }
 }
 
+// Repro from #50465
+
+type Column<T> = (keyof T extends never ? { id?: number | string } : { id: T }) & { title?: string; }
+>Column : Symbol(Column, Decl(controlFlowGenericTypes.ts, 210, 1))
+>T : Symbol(T, Decl(controlFlowGenericTypes.ts, 214, 12))
+>T : Symbol(T, Decl(controlFlowGenericTypes.ts, 214, 12))
+>id : Symbol(id, Decl(controlFlowGenericTypes.ts, 214, 43))
+>id : Symbol(id, Decl(controlFlowGenericTypes.ts, 214, 70))
+>T : Symbol(T, Decl(controlFlowGenericTypes.ts, 214, 12))
+>title : Symbol(title, Decl(controlFlowGenericTypes.ts, 214, 83))
+
+function getColumnProperty<T>(column: Column<T>, key: keyof Column<T>) {
+>getColumnProperty : Symbol(getColumnProperty, Decl(controlFlowGenericTypes.ts, 214, 101))
+>T : Symbol(T, Decl(controlFlowGenericTypes.ts, 216, 27))
+>column : Symbol(column, Decl(controlFlowGenericTypes.ts, 216, 30))
+>Column : Symbol(Column, Decl(controlFlowGenericTypes.ts, 210, 1))
+>T : Symbol(T, Decl(controlFlowGenericTypes.ts, 216, 27))
+>key : Symbol(key, Decl(controlFlowGenericTypes.ts, 216, 48))
+>Column : Symbol(Column, Decl(controlFlowGenericTypes.ts, 210, 1))
+>T : Symbol(T, Decl(controlFlowGenericTypes.ts, 216, 27))
+
+  return column[key];
+>column : Symbol(column, Decl(controlFlowGenericTypes.ts, 216, 30))
+>key : Symbol(key, Decl(controlFlowGenericTypes.ts, 216, 48))
+}
+

tests/baselines/reference/controlFlowGenericTypes.types

@@ -583,3 +583,22 @@ function update<T extends Control, K extends keyof T>(control : T | undefined, k
     }
 }
 
+// Repro from #50465
+
+type Column<T> = (keyof T extends never ? { id?: number | string } : { id: T }) & { title?: string; }
+>Column : Column<T>
+>id : string | number | undefined
+>id : T
+>title : string | undefined
+
+function getColumnProperty<T>(column: Column<T>, key: keyof Column<T>) {
+>getColumnProperty : <T>(column: Column<T>, key: keyof Column<T>) => Column<T>["title" | keyof (keyof T extends never ? { id?: string | number | undefined; } : { id: T; })]
+>column : Column<T>
+>key : "title" | keyof (keyof T extends never ? { id?: string | number | undefined; } : { id: T; })
+
+  return column[key];
+>column[key] : Column<T>["title" | keyof (keyof T extends never ? { id?: string | number | undefined; } : { id: T; })]
+>column : Column<T>
+>key : "title" | keyof (keyof T extends never ? { id?: string | number | undefined; } : { id: T; })
+}
+

tests/cases/conformance/controlFlow/controlFlowGenericTypes.ts

@@ -211,3 +211,11 @@ function update<T extends Control, K extends keyof T>(control : T | undefined, k
         control[key] = value;
     }
 }
+
+// Repro from #50465
+
+type Column<T> = (keyof T extends never ? { id?: number | string } : { id: T }) & { title?: string; }
+
+function getColumnProperty<T>(column: Column<T>, key: keyof Column<T>) {
+  return column[key];
+}