Don't treat return as a yield

src/compiler/checker.ts

@@ -18304,10 +18304,10 @@ namespace ts {
                 }
             }
             else {
-                let types = checkAndAggregateReturnExpressionTypes(func, checkMode);
+                let types: Type[];
                 if (functionFlags & FunctionFlags.Generator) { // Generator or AsyncGenerator function
-                    types = concatenate(checkAndAggregateYieldOperandTypes(func, checkMode), types);
-                    if (!types || types.length === 0) {
+                    types = checkAndAggregateYieldOperandTypes(func, checkMode);
+                    if (types.length === 0) {
                         const iterableIteratorAny = functionFlags & FunctionFlags.Async
                             ? createAsyncIterableIteratorType(anyType) // AsyncGenerator function
                             : createIterableIteratorType(anyType); // Generator function
@@ -18319,6 +18319,7 @@ namespace ts {
                     }
                 }
                 else {
+                    types = checkAndAggregateReturnExpressionTypes(func, checkMode);
                     if (!types) {
                         // For an async function, the return type will not be never, but rather a Promise for never.
                         return functionFlags & FunctionFlags.Async
@@ -18394,7 +18395,7 @@ namespace ts {
                             ? Diagnostics.Type_of_iterated_elements_of_a_yield_Asterisk_operand_must_either_be_a_valid_promise_or_must_not_contain_a_callable_then_member
                             : Diagnostics.Type_of_yield_operand_in_an_async_generator_must_either_be_a_valid_promise_or_must_not_contain_a_callable_then_member);
                     }
-                    pushIfUnique(aggregatedTypes, type);
+                    aggregatedTypes.push(type);
                 }
             });
 

tests/baselines/reference/emitter.asyncGenerators.classMethods.es2015.types

@@ -80,7 +80,7 @@ class C7 {
 >C7 : C7
 
     async * f() {
->f : () => AsyncIterableIterator<number>
+>f : () => AsyncIterableIterator<any>
 
         return 1;
 >1 : 1

tests/baselines/reference/emitter.asyncGenerators.classMethods.es5.types

@@ -80,7 +80,7 @@ class C7 {
 >C7 : C7
 
     async * f() {
->f : () => AsyncIterableIterator<number>
+>f : () => AsyncIterableIterator<any>
 
         return 1;
 >1 : 1

tests/baselines/reference/emitter.asyncGenerators.classMethods.esnext.types

@@ -80,7 +80,7 @@ class C7 {
 >C7 : C7
 
     async * f() {
->f : () => AsyncIterableIterator<number>
+>f : () => AsyncIterableIterator<any>
 
         return 1;
 >1 : 1

tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es2015.types

@@ -53,7 +53,7 @@ async function * f6() {
 }
 === tests/cases/conformance/emitter/es2015/asyncGenerators/F7.ts ===
 async function * f7() {
->f7 : () => AsyncIterableIterator<number>
+>f7 : () => AsyncIterableIterator<any>
 
     return 1;
 >1 : 1

tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es5.types

@@ -53,7 +53,7 @@ async function * f6() {
 }
 === tests/cases/conformance/emitter/es5/asyncGenerators/F7.ts ===
 async function * f7() {
->f7 : () => AsyncIterableIterator<number>
+>f7 : () => AsyncIterableIterator<any>
 
     return 1;
 >1 : 1

tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.esnext.types

@@ -53,7 +53,7 @@ async function * f6() {
 }
 === tests/cases/conformance/emitter/esnext/asyncGenerators/F7.ts ===
 async function * f7() {
->f7 : () => AsyncIterableIterator<number>
+>f7 : () => AsyncIterableIterator<any>
 
     return 1;
 >1 : 1

tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es2015.types

@@ -59,8 +59,8 @@ const f6 = async function * () {
 }
 === tests/cases/conformance/emitter/es2015/asyncGenerators/F7.ts ===
 const f7 = async function * () {
->f7 : () => AsyncIterableIterator<number>
->async function * () {    return 1;} : () => AsyncIterableIterator<number>
+>f7 : () => AsyncIterableIterator<any>
+>async function * () {    return 1;} : () => AsyncIterableIterator<any>
 
     return 1;
 >1 : 1

tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es5.types

@@ -59,8 +59,8 @@ const f6 = async function * () {
 }
 === tests/cases/conformance/emitter/es5/asyncGenerators/F7.ts ===
 const f7 = async function * () {
->f7 : () => AsyncIterableIterator<number>
->async function * () {    return 1;} : () => AsyncIterableIterator<number>
+>f7 : () => AsyncIterableIterator<any>
+>async function * () {    return 1;} : () => AsyncIterableIterator<any>
 
     return 1;
 >1 : 1

tests/baselines/reference/emitter.asyncGenerators.functionExpressions.esnext.types

@@ -59,8 +59,8 @@ const f6 = async function * () {
 }
 === tests/cases/conformance/emitter/esnext/asyncGenerators/F7.ts ===
 const f7 = async function * () {
->f7 : () => AsyncIterableIterator<number>
->async function * () {    return 1;} : () => AsyncIterableIterator<number>
+>f7 : () => AsyncIterableIterator<any>
+>async function * () {    return 1;} : () => AsyncIterableIterator<any>
 
     return 1;
 >1 : 1

tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es2015.types

@@ -83,11 +83,11 @@ const o6 = {
 }
 === tests/cases/conformance/emitter/es2015/asyncGenerators/O7.ts ===
 const o7 = {
->o7 : { f(): AsyncIterableIterator<number>; }
->{    async * f() {        return 1;    }} : { f(): AsyncIterableIterator<number>; }
+>o7 : { f(): AsyncIterableIterator<any>; }
+>{    async * f() {        return 1;    }} : { f(): AsyncIterableIterator<any>; }
 
     async * f() {
->f : () => AsyncIterableIterator<number>
+>f : () => AsyncIterableIterator<any>
 
         return 1;
 >1 : 1

tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es5.types

@@ -83,11 +83,11 @@ const o6 = {
 }
 === tests/cases/conformance/emitter/es5/asyncGenerators/O7.ts ===
 const o7 = {
->o7 : { f(): AsyncIterableIterator<number>; }
->{    async * f() {        return 1;    }} : { f(): AsyncIterableIterator<number>; }
+>o7 : { f(): AsyncIterableIterator<any>; }
+>{    async * f() {        return 1;    }} : { f(): AsyncIterableIterator<any>; }
 
     async * f() {
->f : () => AsyncIterableIterator<number>
+>f : () => AsyncIterableIterator<any>
 
         return 1;
 >1 : 1

tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.esnext.types

@@ -83,11 +83,11 @@ const o6 = {
 }
 === tests/cases/conformance/emitter/esnext/asyncGenerators/O7.ts ===
 const o7 = {
->o7 : { f(): AsyncIterableIterator<number>; }
->{    async * f() {        return 1;    }} : { f(): AsyncIterableIterator<number>; }
+>o7 : { f(): AsyncIterableIterator<any>; }
+>{    async * f() {        return 1;    }} : { f(): AsyncIterableIterator<any>; }
 
     async * f() {
->f : () => AsyncIterableIterator<number>
+>f : () => AsyncIterableIterator<any>
 
         return 1;
 >1 : 1

tests/baselines/reference/generatorTypeCheck14.types

@@ -1,6 +1,6 @@
 === tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck14.ts ===
 function* g() {
->g : () => IterableIterator<0 | "">
+>g : () => IterableIterator<number>
 
     yield 0;
 >yield 0 : any

tests/baselines/reference/generatorTypeCheck15.types

@@ -1,6 +1,6 @@
 === tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck15.ts ===
 function* g() {
->g : () => IterableIterator<string>
+>g : () => IterableIterator<any>
 
     return "";
 >"" : ""

tests/baselines/reference/generatorTypeCheck34.types

@@ -7,7 +7,7 @@ function* g() {
 >0 : 0
 
     function* g2() {
->g2 : () => IterableIterator<string>
+>g2 : () => IterableIterator<any>
 
         return "";
 >"" : ""

tests/baselines/reference/generatorTypeCheck62.errors.txt

@@ -0,0 +1,45 @@
+tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck62.ts(24,70): error TS7025: Generator implicitly has type 'IterableIterator<any>' because it does not yield any values. Consider supplying a return type.
+tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck62.ts(32,70): error TS7025: Generator implicitly has type 'IterableIterator<any>' because it does not yield any values. Consider supplying a return type.
+
+
+==== tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck62.ts (2 errors) ====
+    export interface StrategicState {
+        lastStrategyApplied?: string;
+    }
+
+    export function strategy<T extends StrategicState>(stratName: string, gen: (a: T) => IterableIterator<T | undefined>): (a: T) => IterableIterator<T | undefined> {
+        return function*(state) {
+            for (const next of gen(state)) {
+                if (next) {
+                    next.lastStrategyApplied = stratName;
+                }
+                yield next;
+            }
+        }
+    }
+
+    export interface Strategy<T> {
+        (a: T): IterableIterator<T | undefined>;
+    }
+
+    export interface State extends StrategicState {
+        foo: number;
+    }
+
+    export const Nothing1: Strategy<State> = strategy("Nothing", function*(state: State) {
+                                                                         ~
+!!! error TS7025: Generator implicitly has type 'IterableIterator<any>' because it does not yield any values. Consider supplying a return type.
+        return state;
+    });
+
+    export const Nothing2: Strategy<State> = strategy("Nothing", function*(state: State) {
+        yield state;
+    });
+
+    export const Nothing3: Strategy<State> = strategy("Nothing", function* (state: State) {
+                                                                         ~
+!!! error TS7025: Generator implicitly has type 'IterableIterator<any>' because it does not yield any values. Consider supplying a return type.
+        yield ;
+        return state;
+    });
+

tests/baselines/reference/generatorTypeCheck62.types

@@ -71,10 +71,10 @@ export const Nothing1: Strategy<State> = strategy("Nothing", function*(state: St
 >Nothing1 : Strategy<State>
 >Strategy : Strategy<T>
 >State : State
->strategy("Nothing", function*(state: State) {    return state;}) : (a: State) => IterableIterator<State>
+>strategy("Nothing", function*(state: State) {    return state;}) : (a: any) => IterableIterator<any>
 >strategy : <T extends StrategicState>(stratName: string, gen: (a: T) => IterableIterator<T>) => (a: T) => IterableIterator<T>
 >"Nothing" : "Nothing"
->function*(state: State) {    return state;} : (state: State) => IterableIterator<State>
+>function*(state: State) {    return state;} : (state: State) => IterableIterator<any>
 >state : State
 >State : State
 
@@ -104,10 +104,10 @@ export const Nothing3: Strategy<State> = strategy("Nothing", function* (state: S
 >Nothing3 : Strategy<State>
 >Strategy : Strategy<T>
 >State : State
->strategy("Nothing", function* (state: State) {    yield ;    return state;}) : (a: State) => IterableIterator<State>
+>strategy("Nothing", function* (state: State) {    yield ;    return state;}) : (a: any) => IterableIterator<any>
 >strategy : <T extends StrategicState>(stratName: string, gen: (a: T) => IterableIterator<T>) => (a: T) => IterableIterator<T>
 >"Nothing" : "Nothing"
->function* (state: State) {    yield ;    return state;} : (state: State) => IterableIterator<State>
+>function* (state: State) {    yield ;    return state;} : (state: State) => IterableIterator<any>
 >state : State
 >State : State
 

tests/baselines/reference/generatorTypeCheck63.errors.txt

@@ -1,16 +1,11 @@
-tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck63.ts(24,61): error TS2345: Argument of type '(state: State) => IterableIterator<State | 1>' is not assignable to parameter of type '(a: StrategicState) => IterableIterator<StrategicState>'.
-  Type 'IterableIterator<State | 1>' is not assignable to type 'IterableIterator<StrategicState>'.
-    Type 'State | 1' is not assignable to type 'StrategicState'.
-      Type '1' has no properties in common with type 'StrategicState'.
-tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck63.ts(29,70): error TS7025: Generator implicitly has type 'IterableIterator<any>' because it does not yield any values. Consider supplying a return type.
-tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck63.ts(32,62): error TS2345: Argument of type '(state: State) => IterableIterator<number>' is not assignable to parameter of type '(a: State) => IterableIterator<State>'.
+tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck63.ts(24,61): error TS2345: Argument of type '(state: State) => IterableIterator<number>' is not assignable to parameter of type '(a: State) => IterableIterator<State>'.
   Type 'IterableIterator<number>' is not assignable to type 'IterableIterator<State>'.
     Type 'number' is not assignable to type 'State'.
-tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck63.ts(36,62): error TS2345: Argument of type '(state: State) => IterableIterator<State | 1>' is not assignable to parameter of type '(a: StrategicState) => IterableIterator<StrategicState>'.
-  Type 'IterableIterator<State | 1>' is not assignable to type 'IterableIterator<StrategicState>'.
+tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck63.ts(29,70): error TS7025: Generator implicitly has type 'IterableIterator<any>' because it does not yield any values. Consider supplying a return type.
+tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck63.ts(32,70): error TS7025: Generator implicitly has type 'IterableIterator<any>' because it does not yield any values. Consider supplying a return type.
 
 
-==== tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck63.ts (4 errors) ====
+==== tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck63.ts (3 errors) ====
     export interface StrategicState {
         lastStrategyApplied?: string;
     }
@@ -36,10 +31,9 @@ tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck63.ts(36,62): err
 
     export const Nothing: Strategy<State> = strategy("Nothing", function* (state: State) {
                                                                 ~~~~~~~~
-!!! error TS2345: Argument of type '(state: State) => IterableIterator<State | 1>' is not assignable to parameter of type '(a: StrategicState) => IterableIterator<StrategicState>'.
-!!! error TS2345:   Type 'IterableIterator<State | 1>' is not assignable to type 'IterableIterator<StrategicState>'.
-!!! error TS2345:     Type 'State | 1' is not assignable to type 'StrategicState'.
-!!! error TS2345:       Type '1' has no properties in common with type 'StrategicState'.
+!!! error TS2345: Argument of type '(state: State) => IterableIterator<number>' is not assignable to parameter of type '(a: State) => IterableIterator<State>'.
+!!! error TS2345:   Type 'IterableIterator<number>' is not assignable to type 'IterableIterator<State>'.
+!!! error TS2345:     Type 'number' is not assignable to type 'State'.
         yield 1;
         return state;
     });
@@ -50,17 +44,12 @@ tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck63.ts(36,62): err
     });
 
     export const Nothing2: Strategy<State> = strategy("Nothing", function* (state: State) {
-                                                                 ~~~~~~~~
-!!! error TS2345: Argument of type '(state: State) => IterableIterator<number>' is not assignable to parameter of type '(a: State) => IterableIterator<State>'.
-!!! error TS2345:   Type 'IterableIterator<number>' is not assignable to type 'IterableIterator<State>'.
-!!! error TS2345:     Type 'number' is not assignable to type 'State'.
+                                                                         ~
+!!! error TS7025: Generator implicitly has type 'IterableIterator<any>' because it does not yield any values. Consider supplying a return type.
         return 1;
     });
 
     export const Nothing3: Strategy<State> = strategy("Nothing", function* (state: State) {
-                                                                 ~~~~~~~~
-!!! error TS2345: Argument of type '(state: State) => IterableIterator<State | 1>' is not assignable to parameter of type '(a: StrategicState) => IterableIterator<StrategicState>'.
-!!! error TS2345:   Type 'IterableIterator<State | 1>' is not assignable to type 'IterableIterator<StrategicState>'.
         yield state;
         return 1;
     });

tests/baselines/reference/generatorTypeCheck63.types

@@ -74,7 +74,7 @@ export const Nothing: Strategy<State> = strategy("Nothing", function* (state: St
 >strategy("Nothing", function* (state: State) {    yield 1;    return state;}) : any
 >strategy : <T extends StrategicState>(stratName: string, gen: (a: T) => IterableIterator<T>) => (a: T) => IterableIterator<T>
 >"Nothing" : "Nothing"
->function* (state: State) {    yield 1;    return state;} : (state: State) => IterableIterator<State | 1>
+>function* (state: State) {    yield 1;    return state;} : (state: State) => IterableIterator<number>
 >state : State
 >State : State
 
@@ -104,10 +104,10 @@ export const Nothing2: Strategy<State> = strategy("Nothing", function* (state: S
 >Nothing2 : Strategy<State>
 >Strategy : Strategy<T>
 >State : State
->strategy("Nothing", function* (state: State) {    return 1;}) : any
+>strategy("Nothing", function* (state: State) {    return 1;}) : (a: any) => IterableIterator<any>
 >strategy : <T extends StrategicState>(stratName: string, gen: (a: T) => IterableIterator<T>) => (a: T) => IterableIterator<T>
 >"Nothing" : "Nothing"
->function* (state: State) {    return 1;} : (state: State) => IterableIterator<number>
+>function* (state: State) {    return 1;} : (state: State) => IterableIterator<any>
 >state : State
 >State : State
 
@@ -120,10 +120,10 @@ export const Nothing3: Strategy<State> = strategy("Nothing", function* (state: S
 >Nothing3 : Strategy<State>
 >Strategy : Strategy<T>
 >State : State
->strategy("Nothing", function* (state: State) {    yield state;    return 1;}) : any
+>strategy("Nothing", function* (state: State) {    yield state;    return 1;}) : (a: State) => IterableIterator<State>
 >strategy : <T extends StrategicState>(stratName: string, gen: (a: T) => IterableIterator<T>) => (a: T) => IterableIterator<T>
 >"Nothing" : "Nothing"
->function* (state: State) {    yield state;    return 1;} : (state: State) => IterableIterator<State | 1>
+>function* (state: State) {    yield state;    return 1;} : (state: State) => IterableIterator<State>
 >state : State
 >State : State