Get narrowable types for new expressions (microsoft#57382)

Author: Andarist

src/compiler/checker.ts

@@ -29071,6 +29071,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         return parent.kind === SyntaxKind.PropertyAccessExpression ||
             parent.kind === SyntaxKind.QualifiedName ||
             parent.kind === SyntaxKind.CallExpression && (parent as CallExpression).expression === node ||
+            parent.kind === SyntaxKind.NewExpression && (parent as NewExpression).expression === node ||
             parent.kind === SyntaxKind.ElementAccessExpression && (parent as ElementAccessExpression).expression === node &&
                 !(someType(type, isGenericTypeWithoutNullableConstraint) && isGenericIndexType(getTypeOfExpression((parent as ElementAccessExpression).argumentExpression)));
     }

tests/baselines/reference/typeVariableTypeGuards.js

@@ -82,6 +82,14 @@ function f5<T, K extends keyof T>(obj: T | undefined, key: K) {
         obj[key];
     }
 }
+
+// https://github.com/microsoft/TypeScript/issues/57381
+
+function f6<T extends string | (new () => {})>(a: T) {
+  if (typeof a !== "string") {
+    new a();
+  }
+}
 
 
 //// [typeVariableTypeGuards.js]
@@ -165,3 +173,9 @@ function f5(obj, key) {
         obj[key];
     }
 }
+// https://github.com/microsoft/TypeScript/issues/57381
+function f6(a) {
+    if (typeof a !== "string") {
+        new a();
+    }
+}

tests/baselines/reference/typeVariableTypeGuards.symbols

@@ -221,3 +221,19 @@ function f5<T, K extends keyof T>(obj: T | undefined, key: K) {
     }
 }
 
+// https://github.com/microsoft/TypeScript/issues/57381
+
+function f6<T extends string | (new () => {})>(a: T) {
+>f6 : Symbol(f6, Decl(typeVariableTypeGuards.ts, 80, 1))
+>T : Symbol(T, Decl(typeVariableTypeGuards.ts, 84, 12))
+>a : Symbol(a, Decl(typeVariableTypeGuards.ts, 84, 47))
+>T : Symbol(T, Decl(typeVariableTypeGuards.ts, 84, 12))
+
+  if (typeof a !== "string") {
+>a : Symbol(a, Decl(typeVariableTypeGuards.ts, 84, 47))
+
+    new a();
+>a : Symbol(a, Decl(typeVariableTypeGuards.ts, 84, 47))
+  }
+}
+

tests/baselines/reference/typeVariableTypeGuards.types

@@ -200,3 +200,21 @@ function f5<T, K extends keyof T>(obj: T | undefined, key: K) {
     }
 }
 
+// https://github.com/microsoft/TypeScript/issues/57381
+
+function f6<T extends string | (new () => {})>(a: T) {
+>f6 : <T extends string | (new () => {})>(a: T) => void
+>a : T
+
+  if (typeof a !== "string") {
+>typeof a !== "string" : boolean
+>typeof a : "string" | "number" | "bigint" | "boolean" | "symbol" | "undefined" | "object" | "function"
+>a : T
+>"string" : "string"
+
+    new a();
+>new a() : {}
+>a : new () => {}
+  }
+}
+

tests/cases/compiler/typeVariableTypeGuards.ts

@@ -81,3 +81,11 @@ function f5<T, K extends keyof T>(obj: T | undefined, key: K) {
         obj[key];
     }
 }
+
+// https://github.com/microsoft/TypeScript/issues/57381
+
+function f6<T extends string | (new () => {})>(a: T) {
+  if (typeof a !== "string") {
+    new a();
+  }
+}