Include all flow nodes made within try blocks as antecedents for catch or finally blocks

src/compiler/binder.ts

@@ -100,6 +100,8 @@ namespace ts {
         IsObjectLiteralOrClassExpressionMethod = 1 << 7,
     }
 
+    let flowNodeCreated: <T extends FlowNode>(node: T) => T = identity;
+
     const binder = createBinder();
 
     export function bindSourceFile(file: SourceFile, options: CompilerOptions) {
@@ -530,6 +532,7 @@ namespace ts {
                 blockScopeContainer.locals = undefined;
             }
             if (containerFlags & ContainerFlags.IsControlFlowContainer) {
+                const saveFlowNodeCreated = flowNodeCreated;
                 const saveCurrentFlow = currentFlow;
                 const saveBreakTarget = currentBreakTarget;
                 const saveContinueTarget = currentContinueTarget;
@@ -553,6 +556,7 @@ namespace ts {
                 currentContinueTarget = undefined;
                 activeLabels = undefined;
                 hasExplicitReturn = false;
+                flowNodeCreated = identity;
                 bindChildren(node);
                 // Reset all reachability check related flags on node (for incremental scenarios)
                 node.flags &= ~NodeFlags.ReachabilityAndEmitFlags;
@@ -579,6 +583,7 @@ namespace ts {
                 currentReturnTarget = saveReturnTarget;
                 activeLabels = saveActiveLabels;
                 hasExplicitReturn = saveHasExplicitReturn;
+                flowNodeCreated = saveFlowNodeCreated;
             }
             else if (containerFlags & ContainerFlags.IsInterface) {
                 seenThisKeyword = false;
@@ -858,25 +863,25 @@ namespace ts {
                 return antecedent;
             }
             setFlowNodeReferenced(antecedent);
-            return { flags, expression, antecedent };
+            return flowNodeCreated({ flags, expression, antecedent });
         }
 
         function createFlowSwitchClause(antecedent: FlowNode, switchStatement: SwitchStatement, clauseStart: number, clauseEnd: number): FlowNode {
             if (!isNarrowingExpression(switchStatement.expression)) {
                 return antecedent;
             }
             setFlowNodeReferenced(antecedent);
-            return { flags: FlowFlags.SwitchClause, switchStatement, clauseStart, clauseEnd, antecedent };
+            return flowNodeCreated({ flags: FlowFlags.SwitchClause, switchStatement, clauseStart, clauseEnd, antecedent });
         }
 
         function createFlowAssignment(antecedent: FlowNode, node: Expression | VariableDeclaration | BindingElement): FlowNode {
             setFlowNodeReferenced(antecedent);
-            return { flags: FlowFlags.Assignment, antecedent, node };
+            return flowNodeCreated({ flags: FlowFlags.Assignment, antecedent, node });
         }
 
         function createFlowArrayMutation(antecedent: FlowNode, node: CallExpression | BinaryExpression): FlowNode {
             setFlowNodeReferenced(antecedent);
-            const res: FlowArrayMutation = { flags: FlowFlags.ArrayMutation, antecedent, node };
+            const res: FlowArrayMutation = flowNodeCreated({ flags: FlowFlags.ArrayMutation, antecedent, node });
             return res;
         }
 
@@ -1080,21 +1085,49 @@ namespace ts {
         function bindTryStatement(node: TryStatement): void {
             const preFinallyLabel = createBranchLabel();
             const preTryFlow = currentFlow;
-            // TODO: Every statement in try block is potentially an exit point!
+            const tryPriors: FlowNode[] = [];
+            const oldFlowNodeCreated = flowNodeCreated;
+            // We hook the creation of all flow nodes within the `try` scope and store them so we can add _all_ of them
+            // as possible antecedents of the start of the `catch` or `finally` blocks.
+            // Don't bother intercepting the call if there's no finally or catch block that needs the information
+            if (node.catchClause || node.finallyBlock) {
+                flowNodeCreated = node => (tryPriors.push(node), node);
+            }
             bind(node.tryBlock);
+            flowNodeCreated = oldFlowNodeCreated;
             addAntecedent(preFinallyLabel, currentFlow);
 
             const flowAfterTry = currentFlow;
             let flowAfterCatch = unreachableFlow;
 
             if (node.catchClause) {
                 currentFlow = preTryFlow;
+                if (tryPriors.length) {
+                    const preCatchFlow = createBranchLabel();
+                    addAntecedent(preCatchFlow, currentFlow);
+                    for (const p of tryPriors) {
+                        addAntecedent(preCatchFlow, p);
+                    }
+                    currentFlow = finishFlowLabel(preCatchFlow);
+                }
+
                 bind(node.catchClause);
                 addAntecedent(preFinallyLabel, currentFlow);
 
                 flowAfterCatch = currentFlow;
             }
             if (node.finallyBlock) {
+                // We add the nodes within the `try` block to te `finally`'s antecedents if there's no catch block
+                // (If there is a `catch` block, it will have all these antecedents instead, and the `finally` will
+                // have the end of the `try` block and the end of the `catch` block)
+                if (!node.catchClause) {
+                    if (tryPriors.length) {
+                        for (const p of tryPriors) {
+                            addAntecedent(preFinallyLabel, p);
+                        }
+                    }
+                }
+
                 // in finally flow is combined from pre-try/flow from try/flow from catch
                 // pre-flow is necessary to make sure that finally is reachable even if finally flows in both try and finally blocks are unreachable
 
@@ -1142,7 +1175,7 @@ namespace ts {
                     }
                 }
                 if (!(currentFlow.flags & FlowFlags.Unreachable)) {
-                    const afterFinallyFlow: AfterFinallyFlow = { flags: FlowFlags.AfterFinally, antecedent: currentFlow };
+                    const afterFinallyFlow: AfterFinallyFlow = flowNodeCreated({ flags: FlowFlags.AfterFinally, antecedent: currentFlow });
                     preFinallyFlow.lock = afterFinallyFlow;
                     currentFlow = afterFinallyFlow;
                 }

tests/baselines/reference/controlFlowForCatchAndFinally.js

@@ -0,0 +1,142 @@
+//// [controlFlowForCatchAndFinally.ts]
+type Page = {close(): Promise<void>; content(): Promise<string>};
+type Browser = {close(): Promise<void>};
+declare function test1(): Promise<Browser>;
+declare function test2(obj: Browser): Promise<Page>;
+async function test(): Promise<string> {
+    let browser: Browser | undefined = undefined;
+    let page: Page | undefined = undefined;
+    try {
+        browser = await test1();
+        page = await test2(browser);
+        return await page.content();;
+    } finally {
+        if (page) {
+            await page.close(); // ok
+        }
+
+        if (browser) {
+            await browser.close(); // ok
+        }
+    }
+}
+
+declare class Aborter { abort(): void };
+class Foo {
+    abortController: Aborter | undefined = undefined;
+
+    async operation() {
+        if (this.abortController !== undefined) {
+            this.abortController.abort();
+            this.abortController = undefined;
+        }
+        try {
+            this.abortController = new Aborter();
+        } catch (error) {
+            if (this.abortController !== undefined) {
+                this.abortController.abort(); // ok
+            }
+        }
+    }
+}
+
+//// [controlFlowForCatchAndFinally.js]
+"use strict";
+var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    return new (P || (P = Promise))(function (resolve, reject) {
+        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
+        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
+        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        step((generator = generator.apply(thisArg, _arguments || [])).next());
+    });
+};
+var __generator = (this && this.__generator) || function (thisArg, body) {
+    var _ = { label: 0, sent: function() { if (t[0] & 1) throw t[1]; return t[1]; }, trys: [], ops: [] }, f, y, t, g;
+    return g = { next: verb(0), "throw": verb(1), "return": verb(2) }, typeof Symbol === "function" && (g[Symbol.iterator] = function() { return this; }), g;
+    function verb(n) { return function (v) { return step([n, v]); }; }
+    function step(op) {
+        if (f) throw new TypeError("Generator is already executing.");
+        while (_) try {
+            if (f = 1, y && (t = op[0] & 2 ? y["return"] : op[0] ? y["throw"] || ((t = y["return"]) && t.call(y), 0) : y.next) && !(t = t.call(y, op[1])).done) return t;
+            if (y = 0, t) op = [op[0] & 2, t.value];
+            switch (op[0]) {
+                case 0: case 1: t = op; break;
+                case 4: _.label++; return { value: op[1], done: false };
+                case 5: _.label++; y = op[1]; op = [0]; continue;
+                case 7: op = _.ops.pop(); _.trys.pop(); continue;
+                default:
+                    if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
+                    if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
+                    if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
+                    if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
+                    if (t[2]) _.ops.pop();
+                    _.trys.pop(); continue;
+            }
+            op = body.call(thisArg, _);
+        } catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }
+        if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };
+    }
+};
+function test() {
+    return __awaiter(this, void 0, void 0, function () {
+        var browser, page;
+        return __generator(this, function (_a) {
+            switch (_a.label) {
+                case 0:
+                    browser = undefined;
+                    page = undefined;
+                    _a.label = 1;
+                case 1:
+                    _a.trys.push([1, , 5, 10]);
+                    return [4 /*yield*/, test1()];
+                case 2:
+                    browser = _a.sent();
+                    return [4 /*yield*/, test2(browser)];
+                case 3:
+                    page = _a.sent();
+                    return [4 /*yield*/, page.content()];
+                case 4: return [2 /*return*/, _a.sent()];
+                case 5:
+                    if (!page) return [3 /*break*/, 7];
+                    return [4 /*yield*/, page.close()];
+                case 6:
+                    _a.sent(); // ok
+                    _a.label = 7;
+                case 7:
+                    if (!browser) return [3 /*break*/, 9];
+                    return [4 /*yield*/, browser.close()];
+                case 8:
+                    _a.sent(); // ok
+                    _a.label = 9;
+                case 9: return [7 /*endfinally*/];
+                case 10: return [2 /*return*/];
+            }
+        });
+    });
+}
+;
+var Foo = /** @class */ (function () {
+    function Foo() {
+        this.abortController = undefined;
+    }
+    Foo.prototype.operation = function () {
+        return __awaiter(this, void 0, void 0, function () {
+            return __generator(this, function (_a) {
+                if (this.abortController !== undefined) {
+                    this.abortController.abort();
+                    this.abortController = undefined;
+                }
+                try {
+                    this.abortController = new Aborter();
+                }
+                catch (error) {
+                    if (this.abortController !== undefined) {
+                        this.abortController.abort(); // ok
+                    }
+                }
+                return [2 /*return*/];
+            });
+        });
+    };
+    return Foo;
+}());