Fix control flow loop in yield expression (microsoft#25228)

* Fix control flow loop in yield expression

Yet again, the fix is to stop using checkExpressionCached.

* Update lib in test to reduce number of errors

Author: sandersn

src/compiler/checker.ts

@@ -19911,7 +19911,7 @@ namespace ts {
 
         function getYieldedTypeOfYieldExpression(node: YieldExpression, isAsync: boolean, checkMode?: CheckMode): Type | undefined {
             const errorNode = node.expression || node;
-            const expressionType = node.expression ? checkExpressionCached(node.expression, checkMode) : undefinedWideningType;
+            const expressionType = node.expression ? checkExpression(node.expression, checkMode) : undefinedWideningType;
             // A `yield*` expression effectively yields everything that its operand yields
             const yieldedType = node.asteriskToken ? checkIteratedTypeOrElementType(expressionType, errorNode, /*allowStringInput*/ false, isAsync) : expressionType;
             return !isAsync ? yieldedType : getAwaitedType(yieldedType, errorNode, node.asteriskToken

tests/baselines/reference/yieldExpressionInControlFlow.errors.txt

@@ -0,0 +1,25 @@
+tests/cases/conformance/es6/yieldExpressions/alsoFails.ts(3,9): error TS7034: Variable 'o' implicitly has type 'any[]' in some locations where its type cannot be determined.
+tests/cases/conformance/es6/yieldExpressions/alsoFails.ts(5,20): error TS7005: Variable 'o' implicitly has an 'any[]' type.
+
+
+==== tests/cases/conformance/es6/yieldExpressions/bug25149.js (0 errors) ====
+    function* f() {
+        var o
+        while (true) {
+            o = yield o
+        }
+    }
+    
+==== tests/cases/conformance/es6/yieldExpressions/alsoFails.ts (2 errors) ====
+    // fails in Typescript too
+    function* g() {
+        var o = []
+            ~
+!!! error TS7034: Variable 'o' implicitly has type 'any[]' in some locations where its type cannot be determined.
+        while (true) {
+            o = yield* o
+                       ~
+!!! error TS7005: Variable 'o' implicitly has an 'any[]' type.
+        }
+    }
+    

tests/baselines/reference/yieldExpressionInControlFlow.symbols

@@ -0,0 +1,29 @@
+=== tests/cases/conformance/es6/yieldExpressions/bug25149.js ===
+function* f() {
+>f : Symbol(f, Decl(bug25149.js, 0, 0))
+
+    var o
+>o : Symbol(o, Decl(bug25149.js, 1, 7))
+
+    while (true) {
+        o = yield o
+>o : Symbol(o, Decl(bug25149.js, 1, 7))
+>o : Symbol(o, Decl(bug25149.js, 1, 7))
+    }
+}
+
+=== tests/cases/conformance/es6/yieldExpressions/alsoFails.ts ===
+// fails in Typescript too
+function* g() {
+>g : Symbol(g, Decl(alsoFails.ts, 0, 0))
+
+    var o = []
+>o : Symbol(o, Decl(alsoFails.ts, 2, 7))
+
+    while (true) {
+        o = yield* o
+>o : Symbol(o, Decl(alsoFails.ts, 2, 7))
+>o : Symbol(o, Decl(alsoFails.ts, 2, 7))
+    }
+}
+

tests/baselines/reference/yieldExpressionInControlFlow.types

@@ -0,0 +1,38 @@
+=== tests/cases/conformance/es6/yieldExpressions/bug25149.js ===
+function* f() {
+>f : () => IterableIterator<any>
+
+    var o
+>o : any
+
+    while (true) {
+>true : true
+
+        o = yield o
+>o = yield o : any
+>o : any
+>yield o : any
+>o : any
+    }
+}
+
+=== tests/cases/conformance/es6/yieldExpressions/alsoFails.ts ===
+// fails in Typescript too
+function* g() {
+>g : () => IterableIterator<any>
+
+    var o = []
+>o : any[]
+>[] : undefined[]
+
+    while (true) {
+>true : true
+
+        o = yield* o
+>o = yield* o : any
+>o : any[]
+>yield* o : any
+>o : any
+    }
+}
+

tests/cases/conformance/es6/yieldExpressions/yieldExpressionInControlFlow.ts

@@ -0,0 +1,21 @@
+// @noEmit: true
+// @allowJs: true
+// @checkJs: true
+// @noImplicitAny: true
+// @lib: esnext
+// @Filename: bug25149.js
+function* f() {
+    var o
+    while (true) {
+        o = yield o
+    }
+}
+
+// @Filename: alsoFails.ts
+// fails in Typescript too
+function* g() {
+    var o = []
+    while (true) {
+        o = yield* o
+    }
+}