Merge pull request #9510 from Microsoft/fixSwitchCase

Fix switch case circular reference stack overflow

src/compiler/binder.ts

@@ -551,6 +551,9 @@ namespace ts {
                 case SyntaxKind.CaseBlock:
                     bindCaseBlock(<CaseBlock>node);
                     break;
+                case SyntaxKind.CaseClause:
+                    bindCaseClause(<CaseClause>node);
+                    break;
                 case SyntaxKind.LabeledStatement:
                     bindLabeledStatement(<LabeledStatement>node);
                     break;
@@ -989,6 +992,14 @@ namespace ts {
             }
         }
 
+        function bindCaseClause(node: CaseClause): void {
+            const saveCurrentFlow = currentFlow;
+            currentFlow = preSwitchCaseFlow;
+            bind(node.expression);
+            currentFlow = saveCurrentFlow;
+            forEach(node.statements, bind);
+        }
+
         function pushActiveLabel(name: string, breakTarget: FlowLabel, continueTarget: FlowLabel): ActiveLabel {
             const activeLabel = {
                 name,

tests/baselines/reference/switchCaseCircularRefeference.errors.txt

@@ -0,0 +1,18 @@
+tests/cases/compiler/switchCaseCircularRefeference.ts(5,10): error TS2678: Type '{ a: "A"; b: any; } | { a: "C"; e: any; }' is not comparable to type '"A" | "C"'.
+  Type '{ a: "C"; e: any; }' is not comparable to type '"A" | "C"'.
+    Type '{ a: "C"; e: any; }' is not comparable to type '"C"'.
+
+
+==== tests/cases/compiler/switchCaseCircularRefeference.ts (1 errors) ====
+    // Repro from #9507
+    
+    function f(x: {a: "A", b} | {a: "C", e}) {
+        switch (x.a) {
+        case x:
+             ~
+!!! error TS2678: Type '{ a: "A"; b: any; } | { a: "C"; e: any; }' is not comparable to type '"A" | "C"'.
+!!! error TS2678:   Type '{ a: "C"; e: any; }' is not comparable to type '"A" | "C"'.
+!!! error TS2678:     Type '{ a: "C"; e: any; }' is not comparable to type '"C"'.
+            break;
+        }
+    }

tests/baselines/reference/switchCaseCircularRefeference.js

@@ -0,0 +1,18 @@
+//// [switchCaseCircularRefeference.ts]
+// Repro from #9507
+
+function f(x: {a: "A", b} | {a: "C", e}) {
+    switch (x.a) {
+    case x:
+        break;
+    }
+}
+
+//// [switchCaseCircularRefeference.js]
+// Repro from #9507
+function f(x) {
+    switch (x.a) {
+        case x:
+            break;
+    }
+}

tests/cases/compiler/switchCaseCircularRefeference.ts

@@ -0,0 +1,8 @@
+// Repro from #9507
+
+function f(x: {a: "A", b} | {a: "C", e}) {
+    switch (x.a) {
+    case x:
+        break;
+    }
+}