Fix microsoftGH-32798

Author: hahmadia

src/compiler/checker.ts

@@ -23895,6 +23895,9 @@ namespace ts {
                     assumeTrue = !assumeTrue;
                 }
                 const valueType = getTypeOfExpression(value);
+                if ((type.flags & TypeFlags.Unknown) && (operator === SyntaxKind.EqualsEqualsToken) && (valueType.flags & TypeFlags.Null)) {
+                    return getUnionType([nullType, undefinedType]);
+                }
                 if ((type.flags & TypeFlags.Unknown) && assumeTrue && (operator === SyntaxKind.EqualsEqualsEqualsToken || operator === SyntaxKind.ExclamationEqualsEqualsToken)) {
                     if (valueType.flags & (TypeFlags.Primitive | TypeFlags.NonPrimitive)) {
                         return valueType;

tests/baselines/reference/narrowByEquality.errors.txt

@@ -1,6 +1,6 @@
-tests/cases/compiler/narrowByEquality.ts(53,15): error TS2322: Type 'string | number' is not assignable to type 'number'.
+tests/cases/compiler/narrowByEquality.ts(54,15): error TS2322: Type 'string | number' is not assignable to type 'number'.
   Type 'string' is not assignable to type 'number'.
-tests/cases/compiler/narrowByEquality.ts(54,9): error TS2322: Type 'string | number' is not assignable to type 'number'.
+tests/cases/compiler/narrowByEquality.ts(55,9): error TS2322: Type 'string | number' is not assignable to type 'number'.
   Type 'string' is not assignable to type 'number'.
 
 
@@ -9,6 +9,7 @@ tests/cases/compiler/narrowByEquality.ts(54,9): error TS2322: Type 'string | num
     declare let n: number;
     declare let s: string;
     declare let b: boolean;
+    declare let xUnknown: unknown;
 
     if (x == n) {
         x;
@@ -68,4 +69,9 @@ tests/cases/compiler/narrowByEquality.ts(54,9): error TS2322: Type 'string | num
         }
         return 0;
     }
+    
+    // From issue #32798
+    if (xUnknown == null) {
+        xUnknown;
+    }
 

tests/baselines/reference/narrowByEquality.js

@@ -3,6 +3,7 @@ declare let x: number | string | boolean
 declare let n: number;
 declare let s: string;
 declare let b: boolean;
+declare let xUnknown: unknown;
 
 if (x == n) {
     x;
@@ -56,6 +57,11 @@ function test(level: number | string):number {
     }
     return 0;
 }
+
+// From issue #32798
+if (xUnknown == null) {
+    xUnknown;
+}
 
 
 //// [narrowByEquality.js]
@@ -99,3 +105,7 @@ function test(level) {
     }
     return 0;
 }
+// From issue #32798
+if (xUnknown == null) {
+    xUnknown;
+}

tests/baselines/reference/narrowByEquality.symbols

@@ -11,6 +11,9 @@ declare let s: string;
 declare let b: boolean;
 >b : Symbol(b, Decl(narrowByEquality.ts, 3, 11))
 
+declare let xUnknown: unknown;
+>xUnknown : Symbol(xUnknown, Decl(narrowByEquality.ts, 4, 11))
+
 if (x == n) {
 >x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
 >n : Symbol(n, Decl(narrowByEquality.ts, 1, 11))
@@ -71,43 +74,51 @@ if (x == false) {
 }
 
 declare let xAndObj: number | string | boolean | object
->xAndObj : Symbol(xAndObj, Decl(narrowByEquality.ts, 37, 11))
+>xAndObj : Symbol(xAndObj, Decl(narrowByEquality.ts, 38, 11))
 
 if (xAndObj == {}) {
->xAndObj : Symbol(xAndObj, Decl(narrowByEquality.ts, 37, 11))
+>xAndObj : Symbol(xAndObj, Decl(narrowByEquality.ts, 38, 11))
 
     xAndObj;
->xAndObj : Symbol(xAndObj, Decl(narrowByEquality.ts, 37, 11))
+>xAndObj : Symbol(xAndObj, Decl(narrowByEquality.ts, 38, 11))
 }
 
 if (x == xAndObj) {
 >x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
->xAndObj : Symbol(xAndObj, Decl(narrowByEquality.ts, 37, 11))
+>xAndObj : Symbol(xAndObj, Decl(narrowByEquality.ts, 38, 11))
 
     x;
 >x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
 
     xAndObj;
->xAndObj : Symbol(xAndObj, Decl(narrowByEquality.ts, 37, 11))
+>xAndObj : Symbol(xAndObj, Decl(narrowByEquality.ts, 38, 11))
 }
 
 // Repro from #24991
 
 function test(level: number | string):number {
->test : Symbol(test, Decl(narrowByEquality.ts, 46, 1))
->level : Symbol(level, Decl(narrowByEquality.ts, 50, 14))
+>test : Symbol(test, Decl(narrowByEquality.ts, 47, 1))
+>level : Symbol(level, Decl(narrowByEquality.ts, 51, 14))
 
     if (level == +level) {
->level : Symbol(level, Decl(narrowByEquality.ts, 50, 14))
->level : Symbol(level, Decl(narrowByEquality.ts, 50, 14))
+>level : Symbol(level, Decl(narrowByEquality.ts, 51, 14))
+>level : Symbol(level, Decl(narrowByEquality.ts, 51, 14))
 
         const q2: number = level; // error
->q2 : Symbol(q2, Decl(narrowByEquality.ts, 52, 13))
->level : Symbol(level, Decl(narrowByEquality.ts, 50, 14))
+>q2 : Symbol(q2, Decl(narrowByEquality.ts, 53, 13))
+>level : Symbol(level, Decl(narrowByEquality.ts, 51, 14))
 
         return level;
->level : Symbol(level, Decl(narrowByEquality.ts, 50, 14))
+>level : Symbol(level, Decl(narrowByEquality.ts, 51, 14))
     }
     return 0;
 }
 
+// From issue #32798
+if (xUnknown == null) {
+>xUnknown : Symbol(xUnknown, Decl(narrowByEquality.ts, 4, 11))
+
+    xUnknown;
+>xUnknown : Symbol(xUnknown, Decl(narrowByEquality.ts, 4, 11))
+}
+

tests/baselines/reference/narrowByEquality.types

@@ -11,6 +11,9 @@ declare let s: string;
 declare let b: boolean;
 >b : boolean
 
+declare let xUnknown: unknown;
+>xUnknown : unknown
+
 if (x == n) {
 >x == n : boolean
 >x : string | number | boolean
@@ -130,3 +133,13 @@ function test(level: number | string):number {
 >0 : 0
 }
 
+// From issue #32798
+if (xUnknown == null) {
+>xUnknown == null : boolean
+>xUnknown : unknown
+>null : null
+
+    xUnknown;
+>xUnknown : null | undefined
+}
+

tests/cases/compiler/narrowByEquality.ts

@@ -4,6 +4,7 @@ declare let x: number | string | boolean
 declare let n: number;
 declare let s: string;
 declare let b: boolean;
+declare let xUnknown: unknown;
 
 if (x == n) {
     x;
@@ -57,3 +58,8 @@ function test(level: number | string):number {
     }
     return 0;
 }
+
+// From issue #32798
+if (xUnknown == null) {
+    xUnknown;
+}