Fix crash in CFA when for-in/for-of expression throws

tsc/internal/binder/binder.go

@@ -1907,9 +1907,19 @@ func (b *Binder) bindForStatement(node *ast.Node) {
 
 func (b *Binder) bindForInOrForOfStatement(node *ast.Node) {
 	stmt := node.AsForInOrOfStatement()
+	b.bind(stmt.Expression)
+	if b.currentFlow == b.unreachableFlow {
+		// Like the for-loop initializer, the for-in/for-of expression is bound before the loop's
+		// flow graph is constructed. If it makes flow unreachable (e.g. a throwing IIFE), addAntecedent
+		// will filter out the unreachable entry to preLoopLabel, leaving only the back-edge from the
+		// loop body. This creates a cycle with no exit that crashes isReachableFlowNodeWorker.
+		// Bail out early and just bind the remaining children with unreachable flow.
+		b.bind(stmt.Initializer)
+		b.bind(stmt.Statement)
+		return
+	}
 	preLoopLabel := b.setContinueTarget(node, b.createLoopLabel())
 	postLoopLabel := b.createBranchLabel()
-	b.bind(stmt.Expression)
 	b.addAntecedent(preLoopLabel, b.currentFlow)
 	b.currentFlow = preLoopLabel
 	if node.Kind == ast.KindForOfStatement {

tsc/testdata/baselines/reference/compiler/unreachableFlowAfterThrowingForInOfHead1(allowunreachablecode=false).errors.txt

@@ -0,0 +1,17 @@
+unreachableFlowAfterThrowingForInOfHead1.ts(2,21): error TS2488: Type 'never' must have a '[Symbol.iterator]()' method that returns an iterator.
+unreachableFlowAfterThrowingForInOfHead1.ts(3,9): error TS7027: Unreachable code detected.
+
+
+==== unreachableFlowAfterThrowingForInOfHead1.ts (2 errors) ====
+    try {
+        for (const x of (function () { throw "1"; })()) {
+                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2488: Type 'never' must have a '[Symbol.iterator]()' method that returns an iterator.
+!!! related TS2773 unreachableFlowAfterThrowingForInOfHead1.ts:2:21: Did you forget to use 'await'?
+            console.log("1");
+            ~~~~~~~~~~~~~~~~~
+!!! error TS7027: Unreachable code detected.
+        }
+    }
+    catch (e) { }
+

tsc/testdata/baselines/reference/compiler/unreachableFlowAfterThrowingForInOfHead1(allowunreachablecode=false).symbols

@@ -0,0 +1,16 @@
+//// [tests/cases/compiler/unreachableFlowAfterThrowingForInOfHead1.ts] ////
+
+=== unreachableFlowAfterThrowingForInOfHead1.ts ===
+try {
+    for (const x of (function () { throw "1"; })()) {
+>x : Symbol(x, Decl(unreachableFlowAfterThrowingForInOfHead1.ts, 1, 14))
+
+        console.log("1");
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+    }
+}
+catch (e) { }
+>e : Symbol(e, Decl(unreachableFlowAfterThrowingForInOfHead1.ts, 5, 7))
+

tsc/testdata/baselines/reference/compiler/unreachableFlowAfterThrowingForInOfHead1(allowunreachablecode=false).types

@@ -0,0 +1,22 @@
+//// [tests/cases/compiler/unreachableFlowAfterThrowingForInOfHead1.ts] ////
+
+=== unreachableFlowAfterThrowingForInOfHead1.ts ===
+try {
+    for (const x of (function () { throw "1"; })()) {
+>x : any
+>(function () { throw "1"; })() : never
+>(function () { throw "1"; }) : () => never
+>function () { throw "1"; } : () => never
+>"1" : "1"
+
+        console.log("1");
+>console.log("1") : void
+>console.log : (...data: any[]) => void
+>console : Console
+>log : (...data: any[]) => void
+>"1" : "1"
+    }
+}
+catch (e) { }
+>e : unknown
+

tsc/testdata/baselines/reference/compiler/unreachableFlowAfterThrowingForInOfHead1(allowunreachablecode=true).errors.txt

@@ -0,0 +1,14 @@
+unreachableFlowAfterThrowingForInOfHead1.ts(2,21): error TS2488: Type 'never' must have a '[Symbol.iterator]()' method that returns an iterator.
+
+
+==== unreachableFlowAfterThrowingForInOfHead1.ts (1 errors) ====
+    try {
+        for (const x of (function () { throw "1"; })()) {
+                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2488: Type 'never' must have a '[Symbol.iterator]()' method that returns an iterator.
+!!! related TS2773 unreachableFlowAfterThrowingForInOfHead1.ts:2:21: Did you forget to use 'await'?
+            console.log("1");
+        }
+    }
+    catch (e) { }
+

tsc/testdata/baselines/reference/compiler/unreachableFlowAfterThrowingForInOfHead1(allowunreachablecode=true).symbols

@@ -0,0 +1,16 @@
+//// [tests/cases/compiler/unreachableFlowAfterThrowingForInOfHead1.ts] ////
+
+=== unreachableFlowAfterThrowingForInOfHead1.ts ===
+try {
+    for (const x of (function () { throw "1"; })()) {
+>x : Symbol(x, Decl(unreachableFlowAfterThrowingForInOfHead1.ts, 1, 14))
+
+        console.log("1");
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+    }
+}
+catch (e) { }
+>e : Symbol(e, Decl(unreachableFlowAfterThrowingForInOfHead1.ts, 5, 7))
+

tsc/testdata/baselines/reference/compiler/unreachableFlowAfterThrowingForInOfHead1(allowunreachablecode=true).types

@@ -0,0 +1,22 @@
+//// [tests/cases/compiler/unreachableFlowAfterThrowingForInOfHead1.ts] ////
+
+=== unreachableFlowAfterThrowingForInOfHead1.ts ===
+try {
+    for (const x of (function () { throw "1"; })()) {
+>x : any
+>(function () { throw "1"; })() : never
+>(function () { throw "1"; }) : () => never
+>function () { throw "1"; } : () => never
+>"1" : "1"
+
+        console.log("1");
+>console.log("1") : void
+>console.log : (...data: any[]) => void
+>console : Console
+>log : (...data: any[]) => void
+>"1" : "1"
+    }
+}
+catch (e) { }
+>e : unknown
+

tsc/testdata/baselines/reference/compiler/unreachableFlowAfterThrowingForInOfHead2(allowunreachablecode=false).errors.txt

@@ -0,0 +1,16 @@
+unreachableFlowAfterThrowingForInOfHead2.ts(2,21): error TS2407: The right-hand side of a 'for...in' statement must be of type 'any', an object type or a type parameter, but here has type 'never'.
+unreachableFlowAfterThrowingForInOfHead2.ts(3,9): error TS7027: Unreachable code detected.
+
+
+==== unreachableFlowAfterThrowingForInOfHead2.ts (2 errors) ====
+    try {
+        for (const x in (function () { throw "1"; })()) {
+                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2407: The right-hand side of a 'for...in' statement must be of type 'any', an object type or a type parameter, but here has type 'never'.
+            console.log("1");
+            ~~~~~~~~~~~~~~~~~
+!!! error TS7027: Unreachable code detected.
+        }
+    }
+    catch (e) { }
+

tsc/testdata/baselines/reference/compiler/unreachableFlowAfterThrowingForInOfHead2(allowunreachablecode=false).symbols

@@ -0,0 +1,16 @@
+//// [tests/cases/compiler/unreachableFlowAfterThrowingForInOfHead2.ts] ////
+
+=== unreachableFlowAfterThrowingForInOfHead2.ts ===
+try {
+    for (const x in (function () { throw "1"; })()) {
+>x : Symbol(x, Decl(unreachableFlowAfterThrowingForInOfHead2.ts, 1, 14))
+
+        console.log("1");
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+    }
+}
+catch (e) { }
+>e : Symbol(e, Decl(unreachableFlowAfterThrowingForInOfHead2.ts, 5, 7))
+

tsc/testdata/baselines/reference/compiler/unreachableFlowAfterThrowingForInOfHead2(allowunreachablecode=false).types

@@ -0,0 +1,22 @@
+//// [tests/cases/compiler/unreachableFlowAfterThrowingForInOfHead2.ts] ////
+
+=== unreachableFlowAfterThrowingForInOfHead2.ts ===
+try {
+    for (const x in (function () { throw "1"; })()) {
+>x : string
+>(function () { throw "1"; })() : never
+>(function () { throw "1"; }) : () => never
+>function () { throw "1"; } : () => never
+>"1" : "1"
+
+        console.log("1");
+>console.log("1") : void
+>console.log : (...data: any[]) => void
+>console : Console
+>log : (...data: any[]) => void
+>"1" : "1"
+    }
+}
+catch (e) { }
+>e : unknown
+

tsc/testdata/baselines/reference/compiler/unreachableFlowAfterThrowingForInOfHead2(allowunreachablecode=true).errors.txt

@@ -0,0 +1,13 @@
+unreachableFlowAfterThrowingForInOfHead2.ts(2,21): error TS2407: The right-hand side of a 'for...in' statement must be of type 'any', an object type or a type parameter, but here has type 'never'.
+
+
+==== unreachableFlowAfterThrowingForInOfHead2.ts (1 errors) ====
+    try {
+        for (const x in (function () { throw "1"; })()) {
+                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2407: The right-hand side of a 'for...in' statement must be of type 'any', an object type or a type parameter, but here has type 'never'.
+            console.log("1");
+        }
+    }
+    catch (e) { }
+

tsc/testdata/baselines/reference/compiler/unreachableFlowAfterThrowingForInOfHead2(allowunreachablecode=true).symbols

@@ -0,0 +1,16 @@
+//// [tests/cases/compiler/unreachableFlowAfterThrowingForInOfHead2.ts] ////
+
+=== unreachableFlowAfterThrowingForInOfHead2.ts ===
+try {
+    for (const x in (function () { throw "1"; })()) {
+>x : Symbol(x, Decl(unreachableFlowAfterThrowingForInOfHead2.ts, 1, 14))
+
+        console.log("1");
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+    }
+}
+catch (e) { }
+>e : Symbol(e, Decl(unreachableFlowAfterThrowingForInOfHead2.ts, 5, 7))
+

tsc/testdata/baselines/reference/compiler/unreachableFlowAfterThrowingForInOfHead2(allowunreachablecode=true).types

@@ -0,0 +1,22 @@
+//// [tests/cases/compiler/unreachableFlowAfterThrowingForInOfHead2.ts] ////
+
+=== unreachableFlowAfterThrowingForInOfHead2.ts ===
+try {
+    for (const x in (function () { throw "1"; })()) {
+>x : string
+>(function () { throw "1"; })() : never
+>(function () { throw "1"; }) : () => never
+>function () { throw "1"; } : () => never
+>"1" : "1"
+
+        console.log("1");
+>console.log("1") : void
+>console.log : (...data: any[]) => void
+>console : Console
+>log : (...data: any[]) => void
+>"1" : "1"
+    }
+}
+catch (e) { }
+>e : unknown
+

tsc/testdata/tests/cases/compiler/unreachableFlowAfterThrowingForInOfHead1.ts

@@ -0,0 +1,11 @@
+// @strict: true
+// @noEmit: true
+// @allowUnreachableCode: true, false
+// @target: es2015
+
+try {
+    for (const x of (function () { throw "1"; })()) {
+        console.log("1");
+    }
+}
+catch (e) { }

tsc/testdata/tests/cases/compiler/unreachableFlowAfterThrowingForInOfHead2.ts

@@ -0,0 +1,11 @@
+// @strict: true
+// @noEmit: true
+// @allowUnreachableCode: true, false
+// @target: es2015
+
+try {
+    for (const x in (function () { throw "1"; })()) {
+        console.log("1");
+    }
+}
+catch (e) { }