Add tests

Author: jablko

src/compiler/checker.ts

@@ -3876,7 +3876,7 @@ namespace ts {
                 }
                 if (type.flags & TypeFlags.TypeParameter || objectFlags & ObjectFlags.ClassOrInterface) {
                     if (type.flags & TypeFlags.TypeParameter && contains(context.inferTypeParameters, type)) {
-                        context.approximateLength += (symbolName(type.symbol).length + 6);
+                        context.approximateLength += 6 + (type.symbol ? symbolName(type.symbol).length : 1);
                         return createInferTypeNode(typeParameterToDeclarationWithConstraint(type as TypeParameter, context, /*constraintNode*/ undefined));
                     }
                     if (context.flags & NodeBuilderFlags.GenerateNamesForShadowedTypeParams &&
@@ -4812,7 +4812,7 @@ namespace ts {
                         return cached;
                     }
                 }
-                let result = symbolToName(type.symbol, context, SymbolFlags.Type, /*expectsIdentifier*/ true);
+                let result = type.symbol ? symbolToName(type.symbol, context, SymbolFlags.Type, /*expectsIdentifier*/ true) : createIdentifier("?");
                 if (!(result.kind & SyntaxKind.Identifier)) {
                     return createIdentifier("(Missing type parameter)");
                 }

tests/baselines/reference/asyncArrowFunctionCapturesThis_es2017.types

@@ -6,9 +6,9 @@ class C {
 >method : () => void
 
       var fn = async () => await this;      
->fn : () => Promise<this>
->async () => await this : () => Promise<this>
->await this : this
+>fn : () => Promise<this extends undefined ? this : this extends PromiseLike<infer ?> ? ? : this>
+>async () => await this : () => Promise<this extends undefined ? this : this extends PromiseLike<infer ?> ? ? : this>
+>await this : this extends undefined ? this : this extends PromiseLike<infer ?> ? ? : this
 >this : this
    }
 }

tests/baselines/reference/asyncArrowFunctionCapturesThis_es5.types

@@ -6,9 +6,9 @@ class C {
 >method : () => void
 
       var fn = async () => await this;
->fn : () => Promise<this>
->async () => await this : () => Promise<this>
->await this : this
+>fn : () => Promise<this extends undefined ? this : this extends PromiseLike<infer ?> ? ? : this>
+>async () => await this : () => Promise<this extends undefined ? this : this extends PromiseLike<infer ?> ? ? : this>
+>await this : this extends undefined ? this : this extends PromiseLike<infer ?> ? ? : this
 >this : this
    }
 }

tests/baselines/reference/asyncArrowFunctionCapturesThis_es6.types

@@ -6,9 +6,9 @@ class C {
 >method : () => void
 
       var fn = async () => await this;      
->fn : () => Promise<this>
->async () => await this : () => Promise<this>
->await this : this
+>fn : () => Promise<this extends undefined ? this : this extends PromiseLike<infer ?> ? ? : this>
+>async () => await this : () => Promise<this extends undefined ? this : this extends PromiseLike<infer ?> ? ? : this>
+>await this : this extends undefined ? this : this extends PromiseLike<infer ?> ? ? : this
 >this : this
    }
 }

tests/baselines/reference/asyncFunctionReturnType.js

@@ -73,7 +73,15 @@ async function fGenericIndexedTypeForPromiseOfKProp<TObj extends Obj, K extends
 
 async function fGenericIndexedTypeForExplicitPromiseOfKProp<TObj extends Obj, K extends keyof TObj>(obj: TObj, key: K): Promise<TObj[K]> {
     return Promise.resolve<TObj[K]>(obj[key]);
-}
+}
+
+// #27711
+
+async function fGeneric<T>(x: T) {
+    return x;
+}
+const expected: Promise<string> = fGeneric(undefined as Promise<string>);
+
 
 //// [asyncFunctionReturnType.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
@@ -172,3 +180,10 @@ function fGenericIndexedTypeForExplicitPromiseOfKProp(obj, key) {
         return Promise.resolve(obj[key]);
     });
 }
+// #27711
+function fGeneric(x) {
+    return __awaiter(this, void 0, void 0, function* () {
+        return x;
+    });
+}
+const expected = fGeneric(undefined);

tests/baselines/reference/asyncFunctionReturnType.symbols

@@ -285,3 +285,22 @@ async function fGenericIndexedTypeForExplicitPromiseOfKProp<TObj extends Obj, K
 >obj : Symbol(obj, Decl(asyncFunctionReturnType.ts, 72, 100))
 >key : Symbol(key, Decl(asyncFunctionReturnType.ts, 72, 110))
 }
+
+// #27711
+
+async function fGeneric<T>(x: T) {
+>fGeneric : Symbol(fGeneric, Decl(asyncFunctionReturnType.ts, 74, 1))
+>T : Symbol(T, Decl(asyncFunctionReturnType.ts, 78, 24))
+>x : Symbol(x, Decl(asyncFunctionReturnType.ts, 78, 27))
+>T : Symbol(T, Decl(asyncFunctionReturnType.ts, 78, 24))
+
+    return x;
+>x : Symbol(x, Decl(asyncFunctionReturnType.ts, 78, 27))
+}
+const expected: Promise<string> = fGeneric(undefined as Promise<string>);
+>expected : Symbol(expected, Decl(asyncFunctionReturnType.ts, 81, 5))
+>Promise : Symbol(Promise, Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.promise.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
+>fGeneric : Symbol(fGeneric, Decl(asyncFunctionReturnType.ts, 74, 1))
+>undefined : Symbol(undefined)
+>Promise : Symbol(Promise, Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.promise.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
+

tests/baselines/reference/asyncFunctionReturnType.types

@@ -220,3 +220,20 @@ async function fGenericIndexedTypeForExplicitPromiseOfKProp<TObj extends Obj, K
 >obj : TObj
 >key : K
 }
+
+// #27711
+
+async function fGeneric<T>(x: T) {
+>fGeneric : <T>(x: T) => Promise<T extends undefined ? T : T extends PromiseLike<infer ?> ? ? : T>
+>x : T
+
+    return x;
+>x : T
+}
+const expected: Promise<string> = fGeneric(undefined as Promise<string>);
+>expected : Promise<string>
+>fGeneric(undefined as Promise<string>) : Promise<string>
+>fGeneric : <T>(x: T) => Promise<T extends undefined ? T : T extends PromiseLike<infer ?> ? ? : T>
+>undefined as Promise<string> : Promise<string>
+>undefined : undefined
+

tests/baselines/reference/forAwaitForUnion.types

@@ -4,7 +4,7 @@ async function f<T>(source: Iterable<T> | AsyncIterable<T>) {
 >source : Iterable<T> | AsyncIterable<T>
 
     for await (const x of source) {
->x : T
+>x : T | (T extends undefined ? T : T extends PromiseLike<infer ?> ? ? : T)
 >source : Iterable<T> | AsyncIterable<T>
     }
 }

tests/cases/compiler/asyncFunctionReturnType.ts

@@ -73,4 +73,11 @@ async function fGenericIndexedTypeForPromiseOfKProp<TObj extends Obj, K extends
 
 async function fGenericIndexedTypeForExplicitPromiseOfKProp<TObj extends Obj, K extends keyof TObj>(obj: TObj, key: K): Promise<TObj[K]> {
     return Promise.resolve<TObj[K]>(obj[key]);
-}
+}
+
+// #27711
+
+async function fGeneric<T>(x: T) {
+    return x;
+}
+const expected: Promise<string> = fGeneric(undefined as Promise<string>);