Add special inference rule for 'T | PromiseLike<T>'

Author: rbuckton

src/compiler/checker.ts

@@ -25992,6 +25992,38 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         return isTupleType(type) && getTupleElementType(type, 0) === getIndexedAccessType(typeParameter, getNumberLiteralType(0)) && !getTypeOfPropertyOfType(type, "1" as __String);
     }
 
+    function isAwaitedLikeType(type: Type) {
+        if (type.flags & TypeFlags.Union) {
+            let typeVariable: Type | undefined;
+            let promisedType: Type | undefined;
+            for (const t of (type as UnionType).types) {
+                if (t.flags & TypeFlags.TypeVariable) {
+                    if (typeVariable) {
+                        return false;
+                    }
+                    typeVariable = t;
+                    if (promisedType) {
+                        return typeVariable === promisedType;
+                    }
+                    continue;
+                }
+                if (isPromiseType(t)) {
+                    if (promisedType) {
+                        return false;
+                    }
+                    [promisedType] = getTypeArguments(t as TypeReference);
+                    if (typeVariable) {
+                        return typeVariable === promisedType;
+                    }
+                    continue;
+                }
+                return false;
+            }
+            return true;
+        }
+        return false;
+    }
+
     function inferTypes(inferences: InferenceInfo[], originalSource: Type, originalTarget: Type, priority = InferencePriority.None, contravariant = false) {
         let bivariant = false;
         let propagationType: Type;
@@ -26016,6 +26048,11 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 propagationType = savePropagationType;
                 return;
             }
+            // If the target is either `T | Promise<T>` or `T | PromiseLike<T>`, continue inferring types with the
+            // `AwaitedLikeType` priority.
+            if (!(priority & InferencePriority.AwaitedLikeType) && isAwaitedLikeType(target)) {
+                priority |= InferencePriority.AwaitedLikeType;
+            }
             if (source.aliasSymbol && source.aliasSymbol === target.aliasSymbol) {
                 if (source.aliasTypeArguments) {
                     // Source and target are types originating in the same generic type alias declaration.
@@ -26165,7 +26202,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             }
             if (
                 getObjectFlags(source) & ObjectFlags.Reference && getObjectFlags(target) & ObjectFlags.Reference && (
-                    (source as TypeReference).target === (target as TypeReference).target || isArrayType(source) && isArrayType(target)
+                    (source as TypeReference).target === (target as TypeReference).target ||
+                    isArrayType(source) && isArrayType(target) ||
+                    isPromiseType(source) && isPromiseType(target)
                 ) &&
                 !((source as TypeReference).node && (target as TypeReference).node)
             ) {
@@ -26583,7 +26622,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         function inferFromObjectTypes(source: Type, target: Type) {
             if (
                 getObjectFlags(source) & ObjectFlags.Reference && getObjectFlags(target) & ObjectFlags.Reference && (
-                    (source as TypeReference).target === (target as TypeReference).target || isArrayType(source) && isArrayType(target)
+                    (source as TypeReference).target === (target as TypeReference).target ||
+                    isArrayType(source) && isArrayType(target) ||
+                    isPromiseType(source) && isPromiseType(target)
                 )
             ) {
                 // If source and target are references to the same generic type, infer from type arguments
@@ -42488,6 +42529,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         }
     }
 
+    function isPromiseType(type: Type) {
+        return isReferenceToSomeType(type, [getGlobalPromiseType(/*reportErrors*/ false), getGlobalPromiseLikeType(/*reportErrors*/ false)]);
+    }
+
     function getAwaitedTypeOfPromise(type: Type, errorNode?: Node, diagnosticMessage?: DiagnosticMessage, ...args: DiagnosticArguments): Type | undefined {
         const promisedType = getPromisedTypeOfPromise(type, errorNode);
         return promisedType && getAwaitedType(promisedType, errorNode, diagnosticMessage, ...args);

src/compiler/types.ts

@@ -7027,19 +7027,20 @@ export type TypeMapper =
 export const enum InferencePriority {
     None                         = 0,
     NakedTypeVariable            = 1 << 0,  // Naked type variable in union or intersection type
-    SpeculativeTuple             = 1 << 1,  // Speculative tuple inference
-    SubstituteSource             = 1 << 2,  // Source of inference originated within a substitution type's substitute
-    HomomorphicMappedType        = 1 << 3,  // Reverse inference for homomorphic mapped type
-    PartialHomomorphicMappedType = 1 << 4,  // Partial reverse inference for homomorphic mapped type
-    MappedTypeConstraint         = 1 << 5,  // Reverse inference for mapped type
-    ContravariantConditional     = 1 << 6,  // Conditional type in contravariant position
-    ReturnType                   = 1 << 7,  // Inference made from return type of generic function
-    LiteralKeyof                 = 1 << 8,  // Inference made from a string literal to a keyof T
-    NoConstraints                = 1 << 9,  // Don't infer from constraints of instantiable types
-    AlwaysStrict                 = 1 << 10, // Always use strict rules for contravariant inferences
-    MaxValue                     = 1 << 11, // Seed for inference priority tracking
-
-    PriorityImpliesCombination = ReturnType | MappedTypeConstraint | LiteralKeyof, // These priorities imply that the resulting type should be a combination of all candidates
+    AwaitedLikeType              = 1 << 1,  // A type that is essentially awaited
+    SpeculativeTuple             = 1 << 2,  // Speculative tuple inference
+    SubstituteSource             = 1 << 3,  // Source of inference originated within a substitution type's substitute
+    HomomorphicMappedType        = 1 << 4,  // Reverse inference for homomorphic mapped type
+    PartialHomomorphicMappedType = 1 << 5,  // Partial reverse inference for homomorphic mapped type
+    MappedTypeConstraint         = 1 << 6,  // Reverse inference for mapped type
+    ContravariantConditional     = 1 << 7,  // Conditional type in contravariant position
+    ReturnType                   = 1 << 8,  // Inference made from return type of generic function
+    LiteralKeyof                 = 1 << 9,  // Inference made from a string literal to a keyof T
+    NoConstraints                = 1 << 10, // Don't infer from constraints of instantiable types
+    AlwaysStrict                 = 1 << 11, // Always use strict rules for contravariant inferences
+    MaxValue                     = 1 << 12, // Seed for inference priority tracking
+
+    PriorityImpliesCombination = ReturnType | AwaitedLikeType | MappedTypeConstraint | LiteralKeyof, // These priorities imply that the resulting type should be a combination of all candidates
     Circularity = -1,  // Inference circularity (value less than all other priorities)
 }
 

tests/baselines/reference/api/typescript.d.ts

@@ -6861,18 +6861,19 @@ declare namespace ts {
     enum InferencePriority {
         None = 0,
         NakedTypeVariable = 1,
-        SpeculativeTuple = 2,
-        SubstituteSource = 4,
-        HomomorphicMappedType = 8,
-        PartialHomomorphicMappedType = 16,
-        MappedTypeConstraint = 32,
-        ContravariantConditional = 64,
-        ReturnType = 128,
-        LiteralKeyof = 256,
-        NoConstraints = 512,
-        AlwaysStrict = 1024,
-        MaxValue = 2048,
-        PriorityImpliesCombination = 416,
+        AwaitedLikeType = 2,
+        SpeculativeTuple = 4,
+        SubstituteSource = 8,
+        HomomorphicMappedType = 16,
+        PartialHomomorphicMappedType = 32,
+        MappedTypeConstraint = 64,
+        ContravariantConditional = 128,
+        ReturnType = 256,
+        LiteralKeyof = 512,
+        NoConstraints = 1024,
+        AlwaysStrict = 2048,
+        MaxValue = 4096,
+        PriorityImpliesCombination = 834,
         Circularity = -1,
     }
     interface FileExtensionInfo {

tests/baselines/reference/promiseType.js

@@ -3,6 +3,7 @@
 //// [promiseType.ts]
 declare var p: Promise<boolean>;
 declare var x: any;
+declare var b: bigint;
 
 async function A() {
     const a = await p;
@@ -98,6 +99,7 @@ const p16 = p.catch(() => {});
 const p17 = p.catch(() => {throw 1});
 const p18 = p.catch(() => Promise.reject(1));
 const p19 = p.catch(() => Promise.resolve(1));
+const p19a = p.catch(() => b && Promise.resolve(1));
 
 const p20 = p.then(undefined);
 const p21 = p.then(null);
@@ -108,6 +110,7 @@ const p25 = p.then(() => null);
 const p26 = p.then(() => {});
 const p27 = p.then(() => {throw 1});
 const p28 = p.then(() => Promise.resolve(1));
+const p28a = p.then(() => b && Promise.resolve(1));
 const p29 = p.then(() => Promise.reject(1));
 
 const p30 = p.then(undefined, undefined);
@@ -119,6 +122,7 @@ const p35 = p.then(undefined, () => null);
 const p36 = p.then(undefined, () => {});
 const p37 = p.then(undefined, () => {throw 1});
 const p38 = p.then(undefined, () => Promise.resolve(1));
+const p38a = p.then(undefined, () => b && Promise.resolve(1));
 const p39 = p.then(undefined, () => Promise.reject(1));
 
 const p40 = p.then(null, undefined);
@@ -130,6 +134,7 @@ const p45 = p.then(null, () => null);
 const p46 = p.then(null, () => {});
 const p47 = p.then(null, () => {throw 1});
 const p48 = p.then(null, () => Promise.resolve(1));
+const p48a = p.then(null, () => b && Promise.resolve(1));
 const p49 = p.then(null, () => Promise.reject(1));
 
 const p50 = p.then(() => "1", undefined);
@@ -141,6 +146,7 @@ const p55 = p.then(() => "1", () => null);
 const p56 = p.then(() => "1", () => {});
 const p57 = p.then(() => "1", () => {throw 1});
 const p58 = p.then(() => "1", () => Promise.resolve(1));
+const p58a = p.then(() => "1", () => b && Promise.resolve(1));
 const p59 = p.then(() => "1", () => Promise.reject(1));
 
 const p60 = p.then(() => x, undefined);
@@ -152,6 +158,7 @@ const p65 = p.then(() => x, () => null);
 const p66 = p.then(() => x, () => {});
 const p67 = p.then(() => x, () => {throw 1});
 const p68 = p.then(() => x, () => Promise.resolve(1));
+const p68a = p.then(() => x, () => b && Promise.resolve(1));
 const p69 = p.then(() => x, () => Promise.reject(1));
 
 const p70 = p.then(() => undefined, undefined);
@@ -163,6 +170,7 @@ const p75 = p.then(() => undefined, () => null);
 const p76 = p.then(() => undefined, () => {});
 const p77 = p.then(() => undefined, () => {throw 1});
 const p78 = p.then(() => undefined, () => Promise.resolve(1));
+const p78a = p.then(() => undefined, () => b && Promise.resolve(1));
 const p79 = p.then(() => undefined, () => Promise.reject(1));
 
 const p80 = p.then(() => null, undefined);
@@ -174,6 +182,7 @@ const p85 = p.then(() => null, () => null);
 const p86 = p.then(() => null, () => {});
 const p87 = p.then(() => null, () => {throw 1});
 const p88 = p.then(() => null, () => Promise.resolve(1));
+const p88a = p.then(() => null, () => b && Promise.resolve(1));
 const p89 = p.then(() => null, () => Promise.reject(1));
 
 const p90 = p.then(() => {}, undefined);
@@ -185,6 +194,7 @@ const p95 = p.then(() => {}, () => null);
 const p96 = p.then(() => {}, () => {});
 const p97 = p.then(() => {}, () => {throw 1});
 const p98 = p.then(() => {}, () => Promise.resolve(1));
+const p98a = p.then(() => {}, () => b && Promise.resolve(1));
 const p99 = p.then(() => {}, () => Promise.reject(1));
 
 const pa0 = p.then(() => {throw 1}, undefined);
@@ -196,6 +206,7 @@ const pa5 = p.then(() => {throw 1}, () => null);
 const pa6 = p.then(() => {throw 1}, () => {});
 const pa7 = p.then(() => {throw 1}, () => {throw 1});
 const pa8 = p.then(() => {throw 1}, () => Promise.resolve(1));
+const pa8a = p.then(() => {throw 1}, () => b && Promise.resolve(1));
 const pa9 = p.then(() => {throw 1}, () => Promise.reject(1));
 
 const pb0 = p.then(() => Promise.resolve("1"), undefined);
@@ -207,6 +218,7 @@ const pb5 = p.then(() => Promise.resolve("1"), () => null);
 const pb6 = p.then(() => Promise.resolve("1"), () => {});
 const pb7 = p.then(() => Promise.resolve("1"), () => {throw 1});
 const pb8 = p.then(() => Promise.resolve("1"), () => Promise.resolve(1));
+const pb8a = p.then(() => Promise.resolve("1"), () => b && Promise.resolve(1));
 const pb9 = p.then(() => Promise.resolve("1"), () => Promise.reject(1));
 
 const pc0 = p.then(() => Promise.reject("1"), undefined);
@@ -218,13 +230,15 @@ const pc5 = p.then(() => Promise.reject("1"), () => null);
 const pc6 = p.then(() => Promise.reject("1"), () => {});
 const pc7 = p.then(() => Promise.reject("1"), () => {throw 1});
 const pc8 = p.then(() => Promise.reject("1"), () => Promise.resolve(1));
+const pc8a = p.then(() => Promise.reject("1"), () => b && Promise.resolve(1));
 const pc9 = p.then(() => Promise.reject("1"), () => Promise.reject(1));
 
 Promise.resolve(undefined as Promise<string> | number);
 Promise.resolve(undefined as Promise<Promise<number>>);
 Promise.resolve(undefined as string | Promise<Promise<number>>);
 Promise.resolve(undefined as Promise<string> | Promise<Promise<number>>);
-Promise.resolve(undefined as Promise<string | Promise<Promise<number>>>);
+Promise.resolve(undefined as Promise<string | Promise<Promise<number>>>);
+
 
 //// [promiseType.js]
 var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
@@ -337,6 +351,7 @@ const p16 = p.catch(() => { });
 const p17 = p.catch(() => { throw 1; });
 const p18 = p.catch(() => Promise.reject(1));
 const p19 = p.catch(() => Promise.resolve(1));
+const p19a = p.catch(() => b && Promise.resolve(1));
 const p20 = p.then(undefined);
 const p21 = p.then(null);
 const p22 = p.then(() => 1);
@@ -346,6 +361,7 @@ const p25 = p.then(() => null);
 const p26 = p.then(() => { });
 const p27 = p.then(() => { throw 1; });
 const p28 = p.then(() => Promise.resolve(1));
+const p28a = p.then(() => b && Promise.resolve(1));
 const p29 = p.then(() => Promise.reject(1));
 const p30 = p.then(undefined, undefined);
 const p31 = p.then(undefined, null);
@@ -356,6 +372,7 @@ const p35 = p.then(undefined, () => null);
 const p36 = p.then(undefined, () => { });
 const p37 = p.then(undefined, () => { throw 1; });
 const p38 = p.then(undefined, () => Promise.resolve(1));
+const p38a = p.then(undefined, () => b && Promise.resolve(1));
 const p39 = p.then(undefined, () => Promise.reject(1));
 const p40 = p.then(null, undefined);
 const p41 = p.then(null, null);
@@ -366,6 +383,7 @@ const p45 = p.then(null, () => null);
 const p46 = p.then(null, () => { });
 const p47 = p.then(null, () => { throw 1; });
 const p48 = p.then(null, () => Promise.resolve(1));
+const p48a = p.then(null, () => b && Promise.resolve(1));
 const p49 = p.then(null, () => Promise.reject(1));
 const p50 = p.then(() => "1", undefined);
 const p51 = p.then(() => "1", null);
@@ -376,6 +394,7 @@ const p55 = p.then(() => "1", () => null);
 const p56 = p.then(() => "1", () => { });
 const p57 = p.then(() => "1", () => { throw 1; });
 const p58 = p.then(() => "1", () => Promise.resolve(1));
+const p58a = p.then(() => "1", () => b && Promise.resolve(1));
 const p59 = p.then(() => "1", () => Promise.reject(1));
 const p60 = p.then(() => x, undefined);
 const p61 = p.then(() => x, null);
@@ -386,6 +405,7 @@ const p65 = p.then(() => x, () => null);
 const p66 = p.then(() => x, () => { });
 const p67 = p.then(() => x, () => { throw 1; });
 const p68 = p.then(() => x, () => Promise.resolve(1));
+const p68a = p.then(() => x, () => b && Promise.resolve(1));
 const p69 = p.then(() => x, () => Promise.reject(1));
 const p70 = p.then(() => undefined, undefined);
 const p71 = p.then(() => undefined, null);
@@ -396,6 +416,7 @@ const p75 = p.then(() => undefined, () => null);
 const p76 = p.then(() => undefined, () => { });
 const p77 = p.then(() => undefined, () => { throw 1; });
 const p78 = p.then(() => undefined, () => Promise.resolve(1));
+const p78a = p.then(() => undefined, () => b && Promise.resolve(1));
 const p79 = p.then(() => undefined, () => Promise.reject(1));
 const p80 = p.then(() => null, undefined);
 const p81 = p.then(() => null, null);
@@ -406,6 +427,7 @@ const p85 = p.then(() => null, () => null);
 const p86 = p.then(() => null, () => { });
 const p87 = p.then(() => null, () => { throw 1; });
 const p88 = p.then(() => null, () => Promise.resolve(1));
+const p88a = p.then(() => null, () => b && Promise.resolve(1));
 const p89 = p.then(() => null, () => Promise.reject(1));
 const p90 = p.then(() => { }, undefined);
 const p91 = p.then(() => { }, null);
@@ -416,6 +438,7 @@ const p95 = p.then(() => { }, () => null);
 const p96 = p.then(() => { }, () => { });
 const p97 = p.then(() => { }, () => { throw 1; });
 const p98 = p.then(() => { }, () => Promise.resolve(1));
+const p98a = p.then(() => { }, () => b && Promise.resolve(1));
 const p99 = p.then(() => { }, () => Promise.reject(1));
 const pa0 = p.then(() => { throw 1; }, undefined);
 const pa1 = p.then(() => { throw 1; }, null);
@@ -426,6 +449,7 @@ const pa5 = p.then(() => { throw 1; }, () => null);
 const pa6 = p.then(() => { throw 1; }, () => { });
 const pa7 = p.then(() => { throw 1; }, () => { throw 1; });
 const pa8 = p.then(() => { throw 1; }, () => Promise.resolve(1));
+const pa8a = p.then(() => { throw 1; }, () => b && Promise.resolve(1));
 const pa9 = p.then(() => { throw 1; }, () => Promise.reject(1));
 const pb0 = p.then(() => Promise.resolve("1"), undefined);
 const pb1 = p.then(() => Promise.resolve("1"), null);
@@ -436,6 +460,7 @@ const pb5 = p.then(() => Promise.resolve("1"), () => null);
 const pb6 = p.then(() => Promise.resolve("1"), () => { });
 const pb7 = p.then(() => Promise.resolve("1"), () => { throw 1; });
 const pb8 = p.then(() => Promise.resolve("1"), () => Promise.resolve(1));
+const pb8a = p.then(() => Promise.resolve("1"), () => b && Promise.resolve(1));
 const pb9 = p.then(() => Promise.resolve("1"), () => Promise.reject(1));
 const pc0 = p.then(() => Promise.reject("1"), undefined);
 const pc1 = p.then(() => Promise.reject("1"), null);
@@ -446,6 +471,7 @@ const pc5 = p.then(() => Promise.reject("1"), () => null);
 const pc6 = p.then(() => Promise.reject("1"), () => { });
 const pc7 = p.then(() => Promise.reject("1"), () => { throw 1; });
 const pc8 = p.then(() => Promise.reject("1"), () => Promise.resolve(1));
+const pc8a = p.then(() => Promise.reject("1"), () => b && Promise.resolve(1));
 const pc9 = p.then(() => Promise.reject("1"), () => Promise.reject(1));
 Promise.resolve(undefined);
 Promise.resolve(undefined);