Narrow types by satisfies expressions

src/compiler/checker.ts

@@ -27181,7 +27181,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 return target.kind === SyntaxKind.SuperKeyword;
             case SyntaxKind.NonNullExpression:
             case SyntaxKind.ParenthesizedExpression:
-                return isMatchingReference((source as NonNullExpression | ParenthesizedExpression).expression, target);
+            case SyntaxKind.SatisfiesExpression:
+                return isMatchingReference((source as NonNullExpression | ParenthesizedExpression | SatisfiesExpression).expression, target);
             case SyntaxKind.PropertyAccessExpression:
             case SyntaxKind.ElementAccessExpression:
                 const sourcePropertyName = getAccessedPropertyName(source as AccessExpression);
@@ -29532,7 +29533,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     return narrowTypeByCallExpression(type, expr as CallExpression, assumeTrue);
                 case SyntaxKind.ParenthesizedExpression:
                 case SyntaxKind.NonNullExpression:
-                    return narrowType(type, (expr as ParenthesizedExpression | NonNullExpression).expression, assumeTrue);
+                case SyntaxKind.SatisfiesExpression:
+                    return narrowType(type, (expr as ParenthesizedExpression | NonNullExpression | SatisfiesExpression).expression, assumeTrue);
                 case SyntaxKind.BinaryExpression:
                     return narrowTypeByBinaryExpression(type, expr as BinaryExpression, assumeTrue);
                 case SyntaxKind.PrefixUnaryExpression:

tests/baselines/reference/inferTypePredicates.errors.txt

@@ -333,4 +333,14 @@ inferTypePredicates.ts(205,7): error TS2741: Property 'z' is missing in type 'C1
     if (foobarPred(foobar)) {
       foobar.foo;
     }
+
+    // https://github.com/microsoft/TypeScript/issues/60778
+    const arrTest: Array<number> = [1, 2, null, 3].filter(
+      (x) => (x != null) satisfies boolean,
+    );
+
+    function isEmptyString(x: unknown) {
+      const rv = x === "";
+      return rv satisfies boolean;
+    }
 

tests/baselines/reference/inferTypePredicates.js

@@ -279,6 +279,16 @@ const foobarPred = (fb: typeof foobar) => fb.type === "foo";
 if (foobarPred(foobar)) {
   foobar.foo;
 }
+
+// https://github.com/microsoft/TypeScript/issues/60778
+const arrTest: Array<number> = [1, 2, null, 3].filter(
+  (x) => (x != null) satisfies boolean,
+);
+
+function isEmptyString(x: unknown) {
+  const rv = x === "";
+  return rv satisfies boolean;
+}
 
 
 //// [inferTypePredicates.js]
@@ -538,6 +548,12 @@ var foobarPred = function (fb) { return fb.type === "foo"; };
 if (foobarPred(foobar)) {
     foobar.foo;
 }
+// https://github.com/microsoft/TypeScript/issues/60778
+var arrTest = [1, 2, null, 3].filter(function (x) { return (x != null); });
+function isEmptyString(x) {
+    var rv = x === "";
+    return rv;
+}
 
 
 //// [inferTypePredicates.d.ts]
@@ -630,3 +646,5 @@ declare const foobarPred: (fb: typeof foobar) => fb is {
     type: "foo";
     foo: number;
 };
+declare const arrTest: Array<number>;
+declare function isEmptyString(x: unknown): x is "";

tests/baselines/reference/inferTypePredicates.symbols

@@ -777,3 +777,28 @@ if (foobarPred(foobar)) {
 >foo : Symbol(foo, Decl(inferTypePredicates.ts, 271, 18))
 }
 
+// https://github.com/microsoft/TypeScript/issues/60778
+const arrTest: Array<number> = [1, 2, null, 3].filter(
+>arrTest : Symbol(arrTest, Decl(inferTypePredicates.ts, 280, 5))
+>Array : Symbol(Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>[1, 2, null, 3].filter : Symbol(Array.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>filter : Symbol(Array.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+  (x) => (x != null) satisfies boolean,
+>x : Symbol(x, Decl(inferTypePredicates.ts, 281, 3))
+>x : Symbol(x, Decl(inferTypePredicates.ts, 281, 3))
+
+);
+
+function isEmptyString(x: unknown) {
+>isEmptyString : Symbol(isEmptyString, Decl(inferTypePredicates.ts, 282, 2))
+>x : Symbol(x, Decl(inferTypePredicates.ts, 284, 23))
+
+  const rv = x === "";
+>rv : Symbol(rv, Decl(inferTypePredicates.ts, 285, 7))
+>x : Symbol(x, Decl(inferTypePredicates.ts, 284, 23))
+
+  return rv satisfies boolean;
+>rv : Symbol(rv, Decl(inferTypePredicates.ts, 285, 7))
+}
+

tests/baselines/reference/inferTypePredicates.types

@@ -1649,3 +1649,61 @@ if (foobarPred(foobar)) {
 >    : ^^^^^^
 }
 
+// https://github.com/microsoft/TypeScript/issues/60778
+const arrTest: Array<number> = [1, 2, null, 3].filter(
+>arrTest : number[]
+>        : ^^^^^^^^
+>[1, 2, null, 3].filter(  (x) => (x != null) satisfies boolean,) : number[]
+>                                                                : ^^^^^^^^
+>[1, 2, null, 3].filter : { <S extends number | null>(predicate: (value: number | null, index: number, array: (number | null)[]) => value is S, thisArg?: any): S[]; (predicate: (value: number | null, index: number, array: (number | null)[]) => unknown, thisArg?: any): (number | null)[]; }
+>                       : ^^^ ^^^^^^^^^^^^^^^^^^^^^^^^         ^^^     ^^^^^^^^^^^^^^^^^     ^^      ^^     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^       ^^^   ^^^^^^^^^         ^^^     ^^^^^^^^^^^^^^^^^     ^^      ^^     ^^^^^^^^^^^^^^^^^^^^^^^^       ^^       ^^^   ^^^^^^^^^^^^^^^^^^^^^^^
+>[1, 2, null, 3] : (number | null)[]
+>                : ^^^^^^^^^^^^^^^^^
+>1 : 1
+>  : ^
+>2 : 2
+>  : ^
+>3 : 3
+>  : ^
+>filter : { <S extends number | null>(predicate: (value: number | null, index: number, array: (number | null)[]) => value is S, thisArg?: any): S[]; (predicate: (value: number | null, index: number, array: (number | null)[]) => unknown, thisArg?: any): (number | null)[]; }
+>       : ^^^ ^^^^^^^^^^^^^^^^^^^^^^^^         ^^^     ^^^^^^^^^^^^^^^^^     ^^      ^^     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^       ^^^   ^^^^^^^^^         ^^^     ^^^^^^^^^^^^^^^^^     ^^      ^^     ^^^^^^^^^^^^^^^^^^^^^^^^       ^^       ^^^   ^^^^^^^^^^^^^^^^^^^^^^^
+
+  (x) => (x != null) satisfies boolean,
+>(x) => (x != null) satisfies boolean : (x: number | null) => x is number
+>                                     : ^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+>x : number | null
+>  : ^^^^^^^^^^^^^
+>(x != null) satisfies boolean : boolean
+>                              : ^^^^^^^
+>(x != null) : boolean
+>            : ^^^^^^^
+>x != null : boolean
+>          : ^^^^^^^
+>x : number | null
+>  : ^^^^^^^^^^^^^
+
+);
+
+function isEmptyString(x: unknown) {
+>isEmptyString : (x: unknown) => x is ""
+>              : ^ ^^       ^^^^^^^^^^^^
+>x : unknown
+>  : ^^^^^^^
+
+  const rv = x === "";
+>rv : boolean
+>   : ^^^^^^^
+>x === "" : boolean
+>         : ^^^^^^^
+>x : unknown
+>  : ^^^^^^^
+>"" : ""
+>   : ^^
+
+  return rv satisfies boolean;
+>rv satisfies boolean : boolean
+>                     : ^^^^^^^
+>rv : boolean
+>   : ^^^^^^^
+}
+

tests/cases/compiler/inferTypePredicates.ts

@@ -279,3 +279,13 @@ const foobarPred = (fb: typeof foobar) => fb.type === "foo";
 if (foobarPred(foobar)) {
   foobar.foo;
 }
+
+// https://github.com/microsoft/TypeScript/issues/60778
+const arrTest: Array<number> = [1, 2, null, 3].filter(
+  (x) => (x != null) satisfies boolean,
+);
+
+function isEmptyString(x: unknown) {
+  const rv = x === "";
+  return rv satisfies boolean;
+}