Avoid infinite loop checking yield expression

Andy Hanson · Andy Hanson · commit b2e8a39eb259 · 2018-02-07T09:11:27.000-08:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -19413,12 +19413,18 @@ namespace ts {
         function getTypeOfExpression(node: Expression, cache?: boolean) {
             // Optimize for the common case of a call to a function with a single non-generic call
             // signature where we can just fetch the return type without checking the arguments.
-            if (node.kind === SyntaxKind.CallExpression && (<CallExpression>node).expression.kind !== SyntaxKind.SuperKeyword && !isRequireCall(node, /*checkArgumentIsStringLiteral*/ true) && !isSymbolOrSymbolForCall(node)) {
-                const funcType = checkNonNullExpression((<CallExpression>node).expression);
-                const signature = getSingleCallSignature(funcType);
-                if (signature && !signature.typeParameters) {
-                    return getReturnTypeOfSignature(signature);
-                }
+            switch (node.kind) {
+                case SyntaxKind.CallExpression:
+                    if ((<CallExpression>node).expression.kind !== SyntaxKind.SuperKeyword && !isRequireCall(node, /*checkArgumentIsStringLiteral*/ true) && !isSymbolOrSymbolForCall(node)) {
+                        const funcType = checkNonNullExpression((<CallExpression>node).expression);
+                        const signature = getSingleCallSignature(funcType);
+                        if (signature && !signature.typeParameters) {
+                            return getReturnTypeOfSignature(signature);
+                        }
+                    }
+                    break;
+                case SyntaxKind.YieldExpression:
+                    return anyType;
             }
             // Otherwise simply call checkExpression. Ideally, the entire family of checkXXX functions
             // should have a parameter that indicates whether full error checking is required such that
diff --git a/tests/baselines/reference/yieldExpressionInFlowLoop.js b/tests/baselines/reference/yieldExpressionInFlowLoop.js
@@ -0,0 +1,16 @@
+//// [yieldExpressionInFlowLoop.ts]
+function* f() {
+    let result;
+    while (1) {
+        result = yield result;
+    }
+}
+
+
+//// [yieldExpressionInFlowLoop.js]
+function* f() {
+    let result;
+    while (1) {
+        result = yield result;
+    }
+}
diff --git a/tests/baselines/reference/yieldExpressionInFlowLoop.symbols b/tests/baselines/reference/yieldExpressionInFlowLoop.symbols
@@ -0,0 +1,14 @@
+=== tests/cases/compiler/yieldExpressionInFlowLoop.ts ===
+function* f() {
+>f : Symbol(f, Decl(yieldExpressionInFlowLoop.ts, 0, 0))
+
+    let result;
+>result : Symbol(result, Decl(yieldExpressionInFlowLoop.ts, 1, 7))
+
+    while (1) {
+        result = yield result;
+>result : Symbol(result, Decl(yieldExpressionInFlowLoop.ts, 1, 7))
+>result : Symbol(result, Decl(yieldExpressionInFlowLoop.ts, 1, 7))
+    }
+}
+
diff --git a/tests/baselines/reference/yieldExpressionInFlowLoop.types b/tests/baselines/reference/yieldExpressionInFlowLoop.types
@@ -0,0 +1,18 @@
+=== tests/cases/compiler/yieldExpressionInFlowLoop.ts ===
+function* f() {
+>f : () => IterableIterator<any>
+
+    let result;
+>result : any
+
+    while (1) {
+>1 : 1
+
+        result = yield result;
+>result = yield result : any
+>result : any
+>yield result : any
+>result : any
+    }
+}
+
diff --git a/tests/cases/compiler/yieldExpressionInFlowLoop.ts b/tests/cases/compiler/yieldExpressionInFlowLoop.ts
@@ -0,0 +1,9 @@
+// @noImplicitAny: true
+// @target: es6
+
+function* f() {
+    let result;
+    while (1) {
+        result = yield result;
+    }
+}
