Fix primitive narrowing

src/compiler/types.ts

@@ -2218,7 +2218,10 @@ namespace ts {
         ObjectType = Class | Interface | Reference | Tuple | Anonymous,
         UnionOrIntersection = Union | Intersection,
         StructuredType = ObjectType | Union | Intersection,
-        Narrowable = Any | ObjectType | Union | TypeParameter,
+
+        // 'Narrowable' types are types where narrowing actually narrows.
+        // This *should* be every type other than null, undefined, void, and never
+        Narrowable = Any | StructuredType | TypeParameter | StringLike | NumberLike | Boolean | ESSymbol,
         /* @internal */
         RequiresWidening = ContainsWideningType | ContainsObjectLiteral,
         /* @internal */

tests/baselines/reference/typeGuardNarrowsPrimitiveIntersection.js

@@ -0,0 +1,38 @@
+//// [typeGuardNarrowsPrimitiveIntersection.ts]
+type Tag = {__tag: any};
+declare function isNonBlank(value: string) : value is (string & Tag);
+declare function doThis(value: string & Tag): void;
+declare function doThat(value: string) : void;
+let value: string;
+if (isNonBlank(value)) {
+    doThis(value);
+} else {
+    doThat(value);
+}
+
+
+const enum Tag2 {}
+declare function isNonBlank2(value: string) : value is (string & Tag2);
+declare function doThis2(value: string & Tag2): void;
+declare function doThat2(value: string) : void;
+if (isNonBlank2(value)) {
+    doThis2(value);
+} else {
+    doThat2(value);
+}
+
+
+//// [typeGuardNarrowsPrimitiveIntersection.js]
+var value;
+if (isNonBlank(value)) {
+    doThis(value);
+}
+else {
+    doThat(value);
+}
+if (isNonBlank2(value)) {
+    doThis2(value);
+}
+else {
+    doThat2(value);
+}

tests/baselines/reference/typeGuardNarrowsPrimitiveIntersection.symbols

@@ -0,0 +1,70 @@
+=== tests/cases/conformance/expressions/typeGuards/typeGuardNarrowsPrimitiveIntersection.ts ===
+type Tag = {__tag: any};
+>Tag : Symbol(Tag, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 0, 0))
+>__tag : Symbol(__tag, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 0, 12))
+
+declare function isNonBlank(value: string) : value is (string & Tag);
+>isNonBlank : Symbol(isNonBlank, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 0, 24))
+>value : Symbol(value, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 1, 28))
+>value : Symbol(value, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 1, 28))
+>Tag : Symbol(Tag, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 0, 0))
+
+declare function doThis(value: string & Tag): void;
+>doThis : Symbol(doThis, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 1, 69))
+>value : Symbol(value, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 2, 24))
+>Tag : Symbol(Tag, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 0, 0))
+
+declare function doThat(value: string) : void;
+>doThat : Symbol(doThat, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 2, 51))
+>value : Symbol(value, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 3, 24))
+
+let value: string;
+>value : Symbol(value, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 4, 3))
+
+if (isNonBlank(value)) {
+>isNonBlank : Symbol(isNonBlank, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 0, 24))
+>value : Symbol(value, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 4, 3))
+
+    doThis(value);
+>doThis : Symbol(doThis, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 1, 69))
+>value : Symbol(value, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 4, 3))
+
+} else {
+    doThat(value);
+>doThat : Symbol(doThat, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 2, 51))
+>value : Symbol(value, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 4, 3))
+}
+
+
+const enum Tag2 {}
+>Tag2 : Symbol(Tag2, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 9, 1))
+
+declare function isNonBlank2(value: string) : value is (string & Tag2);
+>isNonBlank2 : Symbol(isNonBlank2, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 12, 18))
+>value : Symbol(value, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 13, 29))
+>value : Symbol(value, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 13, 29))
+>Tag2 : Symbol(Tag2, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 9, 1))
+
+declare function doThis2(value: string & Tag2): void;
+>doThis2 : Symbol(doThis2, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 13, 71))
+>value : Symbol(value, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 14, 25))
+>Tag2 : Symbol(Tag2, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 9, 1))
+
+declare function doThat2(value: string) : void;
+>doThat2 : Symbol(doThat2, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 14, 53))
+>value : Symbol(value, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 15, 25))
+
+if (isNonBlank2(value)) {
+>isNonBlank2 : Symbol(isNonBlank2, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 12, 18))
+>value : Symbol(value, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 4, 3))
+
+    doThis2(value);
+>doThis2 : Symbol(doThis2, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 13, 71))
+>value : Symbol(value, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 4, 3))
+
+} else {
+    doThat2(value);
+>doThat2 : Symbol(doThat2, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 14, 53))
+>value : Symbol(value, Decl(typeGuardNarrowsPrimitiveIntersection.ts, 4, 3))
+}
+

tests/baselines/reference/typeGuardNarrowsPrimitiveIntersection.types

@@ -0,0 +1,76 @@
+=== tests/cases/conformance/expressions/typeGuards/typeGuardNarrowsPrimitiveIntersection.ts ===
+type Tag = {__tag: any};
+>Tag : { __tag: any; }
+>__tag : any
+
+declare function isNonBlank(value: string) : value is (string & Tag);
+>isNonBlank : (value: string) => value is string & { __tag: any; }
+>value : string
+>value : any
+>Tag : { __tag: any; }
+
+declare function doThis(value: string & Tag): void;
+>doThis : (value: string & { __tag: any; }) => void
+>value : string & { __tag: any; }
+>Tag : { __tag: any; }
+
+declare function doThat(value: string) : void;
+>doThat : (value: string) => void
+>value : string
+
+let value: string;
+>value : string
+
+if (isNonBlank(value)) {
+>isNonBlank(value) : boolean
+>isNonBlank : (value: string) => value is string & { __tag: any; }
+>value : string
+
+    doThis(value);
+>doThis(value) : void
+>doThis : (value: string & { __tag: any; }) => void
+>value : string & { __tag: any; }
+
+} else {
+    doThat(value);
+>doThat(value) : void
+>doThat : (value: string) => void
+>value : string
+}
+
+
+const enum Tag2 {}
+>Tag2 : Tag2
+
+declare function isNonBlank2(value: string) : value is (string & Tag2);
+>isNonBlank2 : (value: string) => value is string & Tag2
+>value : string
+>value : any
+>Tag2 : Tag2
+
+declare function doThis2(value: string & Tag2): void;
+>doThis2 : (value: string & Tag2) => void
+>value : string & Tag2
+>Tag2 : Tag2
+
+declare function doThat2(value: string) : void;
+>doThat2 : (value: string) => void
+>value : string
+
+if (isNonBlank2(value)) {
+>isNonBlank2(value) : boolean
+>isNonBlank2 : (value: string) => value is string & Tag2
+>value : string
+
+    doThis2(value);
+>doThis2(value) : void
+>doThis2 : (value: string & Tag2) => void
+>value : string & Tag2
+
+} else {
+    doThat2(value);
+>doThat2(value) : void
+>doThat2 : (value: string) => void
+>value : string
+}
+

tests/baselines/reference/typeGuardNarrowsToLiteralType.js

@@ -0,0 +1,21 @@
+//// [typeGuardNarrowsToLiteralType.ts]
+declare function isFoo(value: string) : value is "foo";
+declare function doThis(value: "foo"): void;
+declare function doThat(value: string) : void;
+let value: string;
+if (isFoo(value)) {
+    doThis(value);
+} else {
+    doThat(value);
+}
+
+
+
+//// [typeGuardNarrowsToLiteralType.js]
+var value;
+if (isFoo(value)) {
+    doThis(value);
+}
+else {
+    doThat(value);
+}

tests/baselines/reference/typeGuardNarrowsToLiteralType.symbols

@@ -0,0 +1,32 @@
+=== tests/cases/conformance/expressions/typeGuards/typeGuardNarrowsToLiteralType.ts ===
+declare function isFoo(value: string) : value is "foo";
+>isFoo : Symbol(isFoo, Decl(typeGuardNarrowsToLiteralType.ts, 0, 0))
+>value : Symbol(value, Decl(typeGuardNarrowsToLiteralType.ts, 0, 23))
+>value : Symbol(value, Decl(typeGuardNarrowsToLiteralType.ts, 0, 23))
+
+declare function doThis(value: "foo"): void;
+>doThis : Symbol(doThis, Decl(typeGuardNarrowsToLiteralType.ts, 0, 55))
+>value : Symbol(value, Decl(typeGuardNarrowsToLiteralType.ts, 1, 24))
+
+declare function doThat(value: string) : void;
+>doThat : Symbol(doThat, Decl(typeGuardNarrowsToLiteralType.ts, 1, 44))
+>value : Symbol(value, Decl(typeGuardNarrowsToLiteralType.ts, 2, 24))
+
+let value: string;
+>value : Symbol(value, Decl(typeGuardNarrowsToLiteralType.ts, 3, 3))
+
+if (isFoo(value)) {
+>isFoo : Symbol(isFoo, Decl(typeGuardNarrowsToLiteralType.ts, 0, 0))
+>value : Symbol(value, Decl(typeGuardNarrowsToLiteralType.ts, 3, 3))
+
+    doThis(value);
+>doThis : Symbol(doThis, Decl(typeGuardNarrowsToLiteralType.ts, 0, 55))
+>value : Symbol(value, Decl(typeGuardNarrowsToLiteralType.ts, 3, 3))
+
+} else {
+    doThat(value);
+>doThat : Symbol(doThat, Decl(typeGuardNarrowsToLiteralType.ts, 1, 44))
+>value : Symbol(value, Decl(typeGuardNarrowsToLiteralType.ts, 3, 3))
+}
+
+

tests/baselines/reference/typeGuardNarrowsToLiteralType.types

@@ -0,0 +1,35 @@
+=== tests/cases/conformance/expressions/typeGuards/typeGuardNarrowsToLiteralType.ts ===
+declare function isFoo(value: string) : value is "foo";
+>isFoo : (value: string) => value is "foo"
+>value : string
+>value : any
+
+declare function doThis(value: "foo"): void;
+>doThis : (value: "foo") => void
+>value : "foo"
+
+declare function doThat(value: string) : void;
+>doThat : (value: string) => void
+>value : string
+
+let value: string;
+>value : string
+
+if (isFoo(value)) {
+>isFoo(value) : boolean
+>isFoo : (value: string) => value is "foo"
+>value : string
+
+    doThis(value);
+>doThis(value) : void
+>doThis : (value: "foo") => void
+>value : "foo"
+
+} else {
+    doThat(value);
+>doThat(value) : void
+>doThat : (value: string) => void
+>value : string
+}
+
+

tests/baselines/reference/typeGuardNarrowsToLiteralTypeUnion.js

@@ -0,0 +1,21 @@
+//// [typeGuardNarrowsToLiteralTypeUnion.ts]
+declare function isFoo(value: string) : value is ("foo" | "bar");
+declare function doThis(value: "foo" | "bar"): void;
+declare function doThat(value: string) : void;
+let value: string;
+if (isFoo(value)) {
+    doThis(value);
+} else {
+    doThat(value);
+}
+
+
+
+//// [typeGuardNarrowsToLiteralTypeUnion.js]
+var value;
+if (isFoo(value)) {
+    doThis(value);
+}
+else {
+    doThat(value);
+}

tests/baselines/reference/typeGuardNarrowsToLiteralTypeUnion.symbols

@@ -0,0 +1,32 @@
+=== tests/cases/conformance/expressions/typeGuards/typeGuardNarrowsToLiteralTypeUnion.ts ===
+declare function isFoo(value: string) : value is ("foo" | "bar");
+>isFoo : Symbol(isFoo, Decl(typeGuardNarrowsToLiteralTypeUnion.ts, 0, 0))
+>value : Symbol(value, Decl(typeGuardNarrowsToLiteralTypeUnion.ts, 0, 23))
+>value : Symbol(value, Decl(typeGuardNarrowsToLiteralTypeUnion.ts, 0, 23))
+
+declare function doThis(value: "foo" | "bar"): void;
+>doThis : Symbol(doThis, Decl(typeGuardNarrowsToLiteralTypeUnion.ts, 0, 65))
+>value : Symbol(value, Decl(typeGuardNarrowsToLiteralTypeUnion.ts, 1, 24))
+
+declare function doThat(value: string) : void;
+>doThat : Symbol(doThat, Decl(typeGuardNarrowsToLiteralTypeUnion.ts, 1, 52))
+>value : Symbol(value, Decl(typeGuardNarrowsToLiteralTypeUnion.ts, 2, 24))
+
+let value: string;
+>value : Symbol(value, Decl(typeGuardNarrowsToLiteralTypeUnion.ts, 3, 3))
+
+if (isFoo(value)) {
+>isFoo : Symbol(isFoo, Decl(typeGuardNarrowsToLiteralTypeUnion.ts, 0, 0))
+>value : Symbol(value, Decl(typeGuardNarrowsToLiteralTypeUnion.ts, 3, 3))
+
+    doThis(value);
+>doThis : Symbol(doThis, Decl(typeGuardNarrowsToLiteralTypeUnion.ts, 0, 65))
+>value : Symbol(value, Decl(typeGuardNarrowsToLiteralTypeUnion.ts, 3, 3))
+
+} else {
+    doThat(value);
+>doThat : Symbol(doThat, Decl(typeGuardNarrowsToLiteralTypeUnion.ts, 1, 52))
+>value : Symbol(value, Decl(typeGuardNarrowsToLiteralTypeUnion.ts, 3, 3))
+}
+
+

tests/baselines/reference/typeGuardNarrowsToLiteralTypeUnion.types

@@ -0,0 +1,35 @@
+=== tests/cases/conformance/expressions/typeGuards/typeGuardNarrowsToLiteralTypeUnion.ts ===
+declare function isFoo(value: string) : value is ("foo" | "bar");
+>isFoo : (value: string) => value is "foo" | "bar"
+>value : string
+>value : any
+
+declare function doThis(value: "foo" | "bar"): void;
+>doThis : (value: "foo" | "bar") => void
+>value : "foo" | "bar"
+
+declare function doThat(value: string) : void;
+>doThat : (value: string) => void
+>value : string
+
+let value: string;
+>value : string
+
+if (isFoo(value)) {
+>isFoo(value) : boolean
+>isFoo : (value: string) => value is "foo" | "bar"
+>value : string
+
+    doThis(value);
+>doThis(value) : void
+>doThis : (value: "foo" | "bar") => void
+>value : "foo" | "bar"
+
+} else {
+    doThat(value);
+>doThat(value) : void
+>doThat : (value: string) => void
+>value : string
+}
+
+