Merge pull request #23782 from Microsoft/controlFlowNullTypeAndLiteral

Control flow for null type vs. literal

src/compiler/checker.ts

@@ -13690,7 +13690,7 @@ namespace ts {
                     const doubleEquals = operator === SyntaxKind.EqualsEqualsToken || operator === SyntaxKind.ExclamationEqualsToken;
                     const facts = doubleEquals ?
                         assumeTrue ? TypeFacts.EQUndefinedOrNull : TypeFacts.NEUndefinedOrNull :
-                        value.kind === SyntaxKind.NullKeyword ?
+                        valueType.flags & TypeFlags.Null ?
                             assumeTrue ? TypeFacts.EQNull : TypeFacts.NENull :
                             assumeTrue ? TypeFacts.EQUndefined : TypeFacts.NEUndefined;
                     return getTypeWithFacts(type, facts);

tests/baselines/reference/controlFlowNullTypeAndLiteral.errors.txt

@@ -0,0 +1,36 @@
+tests/cases/compiler/controlFlowNullTypeAndLiteral.ts(15,12): error TS2345: Argument of type 'null' is not assignable to parameter of type 'number'.
+tests/cases/compiler/controlFlowNullTypeAndLiteral.ts(17,12): error TS2345: Argument of type 'null' is not assignable to parameter of type 'number'.
+tests/cases/compiler/controlFlowNullTypeAndLiteral.ts(21,15): error TS2322: Type 'null' is not assignable to type 'string'.
+
+
+==== tests/cases/compiler/controlFlowNullTypeAndLiteral.ts (3 errors) ====
+    // Repros from #23771
+    
+    const myNull: null = null;
+    const objWithValMaybeNull: { val: number | null } = { val: 1 };
+    const addOne = function (num: number) {
+        return num + 1;
+    }
+    
+    if (objWithValMaybeNull.val !== null)
+        addOne(objWithValMaybeNull.val);
+    if (objWithValMaybeNull.val !== myNull)
+        addOne(objWithValMaybeNull.val);
+    
+    if (objWithValMaybeNull.val === null)
+        addOne(objWithValMaybeNull.val);    // Error
+               ~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2345: Argument of type 'null' is not assignable to parameter of type 'number'.
+    if (objWithValMaybeNull.val === myNull)
+        addOne(objWithValMaybeNull.val);    // Error
+               ~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2345: Argument of type 'null' is not assignable to parameter of type 'number'.
+    
+    function f(x: number | null) {
+        if(x === myNull) {
+            const s: string = x;  // Error
+                  ~
+!!! error TS2322: Type 'null' is not assignable to type 'string'.
+        }
+    }
+    

tests/baselines/reference/controlFlowNullTypeAndLiteral.js

@@ -0,0 +1,47 @@
+//// [controlFlowNullTypeAndLiteral.ts]
+// Repros from #23771
+
+const myNull: null = null;
+const objWithValMaybeNull: { val: number | null } = { val: 1 };
+const addOne = function (num: number) {
+    return num + 1;
+}
+
+if (objWithValMaybeNull.val !== null)
+    addOne(objWithValMaybeNull.val);
+if (objWithValMaybeNull.val !== myNull)
+    addOne(objWithValMaybeNull.val);
+
+if (objWithValMaybeNull.val === null)
+    addOne(objWithValMaybeNull.val);    // Error
+if (objWithValMaybeNull.val === myNull)
+    addOne(objWithValMaybeNull.val);    // Error
+
+function f(x: number | null) {
+    if(x === myNull) {
+        const s: string = x;  // Error
+    }
+}
+
+
+//// [controlFlowNullTypeAndLiteral.js]
+"use strict";
+// Repros from #23771
+var myNull = null;
+var objWithValMaybeNull = { val: 1 };
+var addOne = function (num) {
+    return num + 1;
+};
+if (objWithValMaybeNull.val !== null)
+    addOne(objWithValMaybeNull.val);
+if (objWithValMaybeNull.val !== myNull)
+    addOne(objWithValMaybeNull.val);
+if (objWithValMaybeNull.val === null)
+    addOne(objWithValMaybeNull.val); // Error
+if (objWithValMaybeNull.val === myNull)
+    addOne(objWithValMaybeNull.val); // Error
+function f(x) {
+    if (x === myNull) {
+        var s = x; // Error
+    }
+}

tests/baselines/reference/controlFlowNullTypeAndLiteral.symbols

@@ -0,0 +1,79 @@
+=== tests/cases/compiler/controlFlowNullTypeAndLiteral.ts ===
+// Repros from #23771
+
+const myNull: null = null;
+>myNull : Symbol(myNull, Decl(controlFlowNullTypeAndLiteral.ts, 2, 5))
+
+const objWithValMaybeNull: { val: number | null } = { val: 1 };
+>objWithValMaybeNull : Symbol(objWithValMaybeNull, Decl(controlFlowNullTypeAndLiteral.ts, 3, 5))
+>val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+>val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 53))
+
+const addOne = function (num: number) {
+>addOne : Symbol(addOne, Decl(controlFlowNullTypeAndLiteral.ts, 4, 5))
+>num : Symbol(num, Decl(controlFlowNullTypeAndLiteral.ts, 4, 25))
+
+    return num + 1;
+>num : Symbol(num, Decl(controlFlowNullTypeAndLiteral.ts, 4, 25))
+}
+
+if (objWithValMaybeNull.val !== null)
+>objWithValMaybeNull.val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+>objWithValMaybeNull : Symbol(objWithValMaybeNull, Decl(controlFlowNullTypeAndLiteral.ts, 3, 5))
+>val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+
+    addOne(objWithValMaybeNull.val);
+>addOne : Symbol(addOne, Decl(controlFlowNullTypeAndLiteral.ts, 4, 5))
+>objWithValMaybeNull.val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+>objWithValMaybeNull : Symbol(objWithValMaybeNull, Decl(controlFlowNullTypeAndLiteral.ts, 3, 5))
+>val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+
+if (objWithValMaybeNull.val !== myNull)
+>objWithValMaybeNull.val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+>objWithValMaybeNull : Symbol(objWithValMaybeNull, Decl(controlFlowNullTypeAndLiteral.ts, 3, 5))
+>val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+>myNull : Symbol(myNull, Decl(controlFlowNullTypeAndLiteral.ts, 2, 5))
+
+    addOne(objWithValMaybeNull.val);
+>addOne : Symbol(addOne, Decl(controlFlowNullTypeAndLiteral.ts, 4, 5))
+>objWithValMaybeNull.val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+>objWithValMaybeNull : Symbol(objWithValMaybeNull, Decl(controlFlowNullTypeAndLiteral.ts, 3, 5))
+>val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+
+if (objWithValMaybeNull.val === null)
+>objWithValMaybeNull.val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+>objWithValMaybeNull : Symbol(objWithValMaybeNull, Decl(controlFlowNullTypeAndLiteral.ts, 3, 5))
+>val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+
+    addOne(objWithValMaybeNull.val);    // Error
+>addOne : Symbol(addOne, Decl(controlFlowNullTypeAndLiteral.ts, 4, 5))
+>objWithValMaybeNull.val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+>objWithValMaybeNull : Symbol(objWithValMaybeNull, Decl(controlFlowNullTypeAndLiteral.ts, 3, 5))
+>val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+
+if (objWithValMaybeNull.val === myNull)
+>objWithValMaybeNull.val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+>objWithValMaybeNull : Symbol(objWithValMaybeNull, Decl(controlFlowNullTypeAndLiteral.ts, 3, 5))
+>val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+>myNull : Symbol(myNull, Decl(controlFlowNullTypeAndLiteral.ts, 2, 5))
+
+    addOne(objWithValMaybeNull.val);    // Error
+>addOne : Symbol(addOne, Decl(controlFlowNullTypeAndLiteral.ts, 4, 5))
+>objWithValMaybeNull.val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+>objWithValMaybeNull : Symbol(objWithValMaybeNull, Decl(controlFlowNullTypeAndLiteral.ts, 3, 5))
+>val : Symbol(val, Decl(controlFlowNullTypeAndLiteral.ts, 3, 28))
+
+function f(x: number | null) {
+>f : Symbol(f, Decl(controlFlowNullTypeAndLiteral.ts, 16, 36))
+>x : Symbol(x, Decl(controlFlowNullTypeAndLiteral.ts, 18, 11))
+
+    if(x === myNull) {
+>x : Symbol(x, Decl(controlFlowNullTypeAndLiteral.ts, 18, 11))
+>myNull : Symbol(myNull, Decl(controlFlowNullTypeAndLiteral.ts, 2, 5))
+
+        const s: string = x;  // Error
+>s : Symbol(s, Decl(controlFlowNullTypeAndLiteral.ts, 20, 13))
+>x : Symbol(x, Decl(controlFlowNullTypeAndLiteral.ts, 18, 11))
+    }
+}
+

tests/baselines/reference/controlFlowNullTypeAndLiteral.types

@@ -0,0 +1,99 @@
+=== tests/cases/compiler/controlFlowNullTypeAndLiteral.ts ===
+// Repros from #23771
+
+const myNull: null = null;
+>myNull : null
+>null : null
+>null : null
+
+const objWithValMaybeNull: { val: number | null } = { val: 1 };
+>objWithValMaybeNull : { val: number | null; }
+>val : number | null
+>null : null
+>{ val: 1 } : { val: number; }
+>val : number
+>1 : 1
+
+const addOne = function (num: number) {
+>addOne : (num: number) => number
+>function (num: number) {    return num + 1;} : (num: number) => number
+>num : number
+
+    return num + 1;
+>num + 1 : number
+>num : number
+>1 : 1
+}
+
+if (objWithValMaybeNull.val !== null)
+>objWithValMaybeNull.val !== null : boolean
+>objWithValMaybeNull.val : number | null
+>objWithValMaybeNull : { val: number | null; }
+>val : number | null
+>null : null
+
+    addOne(objWithValMaybeNull.val);
+>addOne(objWithValMaybeNull.val) : number
+>addOne : (num: number) => number
+>objWithValMaybeNull.val : number
+>objWithValMaybeNull : { val: number | null; }
+>val : number
+
+if (objWithValMaybeNull.val !== myNull)
+>objWithValMaybeNull.val !== myNull : boolean
+>objWithValMaybeNull.val : number | null
+>objWithValMaybeNull : { val: number | null; }
+>val : number | null
+>myNull : null
+
+    addOne(objWithValMaybeNull.val);
+>addOne(objWithValMaybeNull.val) : number
+>addOne : (num: number) => number
+>objWithValMaybeNull.val : number
+>objWithValMaybeNull : { val: number | null; }
+>val : number
+
+if (objWithValMaybeNull.val === null)
+>objWithValMaybeNull.val === null : boolean
+>objWithValMaybeNull.val : number | null
+>objWithValMaybeNull : { val: number | null; }
+>val : number | null
+>null : null
+
+    addOne(objWithValMaybeNull.val);    // Error
+>addOne(objWithValMaybeNull.val) : number
+>addOne : (num: number) => number
+>objWithValMaybeNull.val : null
+>objWithValMaybeNull : { val: number | null; }
+>val : null
+
+if (objWithValMaybeNull.val === myNull)
+>objWithValMaybeNull.val === myNull : boolean
+>objWithValMaybeNull.val : number | null
+>objWithValMaybeNull : { val: number | null; }
+>val : number | null
+>myNull : null
+
+    addOne(objWithValMaybeNull.val);    // Error
+>addOne(objWithValMaybeNull.val) : number
+>addOne : (num: number) => number
+>objWithValMaybeNull.val : null
+>objWithValMaybeNull : { val: number | null; }
+>val : null
+
+function f(x: number | null) {
+>f : (x: number | null) => void
+>x : number | null
+>null : null
+
+    if(x === myNull) {
+>x === myNull : boolean
+>x : number | null
+>myNull : null
+
+        const s: string = x;  // Error
+>s : string
+>x : null
+    }
+}
+

tests/cases/compiler/controlFlowNullTypeAndLiteral.ts

@@ -0,0 +1,25 @@
+// @strict: true
+
+// Repros from #23771
+
+const myNull: null = null;
+const objWithValMaybeNull: { val: number | null } = { val: 1 };
+const addOne = function (num: number) {
+    return num + 1;
+}
+
+if (objWithValMaybeNull.val !== null)
+    addOne(objWithValMaybeNull.val);
+if (objWithValMaybeNull.val !== myNull)
+    addOne(objWithValMaybeNull.val);
+
+if (objWithValMaybeNull.val === null)
+    addOne(objWithValMaybeNull.val);    // Error
+if (objWithValMaybeNull.val === myNull)
+    addOne(objWithValMaybeNull.val);    // Error
+
+function f(x: number | null) {
+    if(x === myNull) {
+        const s: string = x;  // Error
+    }
+}