From cdb3763f8e6c966f695ec86eb2fac2f024fa2c08 Mon Sep 17 00:00:00 2001
From: John Favret <64748847+johnfav03@users.noreply.github.com>
Date: Thu, 16 Jul 2026 09:37:36 -0700
Subject: [PATCH] added recursion guard for getexplicittypeofsymbol

---
 internal/checker/checker.go                   |  1 +
 internal/checker/flow.go                      |  4 ++++
 .../forOfSelfReferentialDottedName.errors.txt | 17 +++++++++++++++++
 .../forOfSelfReferentialDottedName.js         | 19 +++++++++++++++++++
 .../forOfSelfReferentialDottedName.symbols    | 16 ++++++++++++++++
 .../forOfSelfReferentialDottedName.types      | 17 +++++++++++++++++
 .../forOfSelfReferentialDottedName.ts         |  6 ++++++
 7 files changed, 80 insertions(+)
 create mode 100644 testdata/baselines/reference/compiler/forOfSelfReferentialDottedName.errors.txt
 create mode 100644 testdata/baselines/reference/compiler/forOfSelfReferentialDottedName.js
 create mode 100644 testdata/baselines/reference/compiler/forOfSelfReferentialDottedName.symbols
 create mode 100644 testdata/baselines/reference/compiler/forOfSelfReferentialDottedName.types
 create mode 100644 testdata/tests/cases/compiler/forOfSelfReferentialDottedName.ts

diff --git a/internal/checker/checker.go b/internal/checker/checker.go
index b639d488e44..f6066b1a6f3 100644
--- a/internal/checker/checker.go
+++ b/internal/checker/checker.go
@@ -642,6 +642,7 @@ type Checker struct {
 	reverseHomomorphicMappedCache               map[ReverseMappedTypeKey]*Type
 	iterationTypesCache                         map[IterationTypesKey]IterationTypes
 	markerTypes                                 collections.Set[*Type]
+	resolvingExplicitTypeOfSymbol               collections.Set[*ast.Symbol]
 	undefinedSymbol                             *ast.Symbol
 	argumentsSymbol                             *ast.Symbol
 	requireSymbol                               *ast.Symbol
diff --git a/internal/checker/flow.go b/internal/checker/flow.go
index b60d9c97075..2aa2019ce77 100644
--- a/internal/checker/flow.go
+++ b/internal/checker/flow.go
@@ -2133,6 +2133,10 @@ func (c *Checker) getTypeOfDottedName(node *ast.Node, diagnostic *ast.Diagnostic
 
 func (c *Checker) getExplicitTypeOfSymbol(symbol *ast.Symbol, diagnostic *ast.Diagnostic) *Type {
 	symbol = c.resolveSymbol(symbol)
+	if !c.resolvingExplicitTypeOfSymbol.AddIfAbsent(symbol) {
+		return nil
+	}
+	defer c.resolvingExplicitTypeOfSymbol.Delete(symbol)
 	if symbol.Flags&(ast.SymbolFlagsFunction|ast.SymbolFlagsMethod|ast.SymbolFlagsClass|ast.SymbolFlagsValueModule) != 0 {
 		return c.getTypeOfSymbol(symbol)
 	}
diff --git a/testdata/baselines/reference/compiler/forOfSelfReferentialDottedName.errors.txt b/testdata/baselines/reference/compiler/forOfSelfReferentialDottedName.errors.txt
new file mode 100644
index 00000000000..877e1001240
--- /dev/null
+++ b/testdata/baselines/reference/compiler/forOfSelfReferentialDottedName.errors.txt
@@ -0,0 +1,17 @@
+forOfSelfReferentialDottedName.ts(3,12): error TS7022: 'a' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.
+forOfSelfReferentialDottedName.ts(3,17): error TS2448: Block-scoped variable 'a' used before its declaration.
+
+
+==== forOfSelfReferentialDottedName.ts (2 errors) ====
+    // A self-referential for-of iterable (`for (const a of a)`) plus a call and a
+    // later narrowing reference must not infinitely recurse in getExplicitTypeOfSymbol.
+    for (const a of a) {
+               ~
+!!! error TS7022: 'a' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.
+                    ~
+!!! error TS2448: Block-scoped variable 'a' used before its declaration.
+!!! related TS2728 forOfSelfReferentialDottedName.ts:3:12: 'a' is declared here.
+        a();
+        a;
+    }
+    
\ No newline at end of file
diff --git a/testdata/baselines/reference/compiler/forOfSelfReferentialDottedName.js b/testdata/baselines/reference/compiler/forOfSelfReferentialDottedName.js
new file mode 100644
index 00000000000..2c42b7ac8d5
--- /dev/null
+++ b/testdata/baselines/reference/compiler/forOfSelfReferentialDottedName.js
@@ -0,0 +1,19 @@
+//// [tests/cases/compiler/forOfSelfReferentialDottedName.ts] ////
+
+//// [forOfSelfReferentialDottedName.ts]
+// A self-referential for-of iterable (`for (const a of a)`) plus a call and a
+// later narrowing reference must not infinitely recurse in getExplicitTypeOfSymbol.
+for (const a of a) {
+    a();
+    a;
+}
+
+
+//// [forOfSelfReferentialDottedName.js]
+"use strict";
+// A self-referential for-of iterable (`for (const a of a)`) plus a call and a
+// later narrowing reference must not infinitely recurse in getExplicitTypeOfSymbol.
+for (const a of a) {
+    a();
+    a;
+}
diff --git a/testdata/baselines/reference/compiler/forOfSelfReferentialDottedName.symbols b/testdata/baselines/reference/compiler/forOfSelfReferentialDottedName.symbols
new file mode 100644
index 00000000000..458bb2b8159
--- /dev/null
+++ b/testdata/baselines/reference/compiler/forOfSelfReferentialDottedName.symbols
@@ -0,0 +1,16 @@
+//// [tests/cases/compiler/forOfSelfReferentialDottedName.ts] ////
+
+=== forOfSelfReferentialDottedName.ts ===
+// A self-referential for-of iterable (`for (const a of a)`) plus a call and a
+// later narrowing reference must not infinitely recurse in getExplicitTypeOfSymbol.
+for (const a of a) {
+>a : Symbol(a, Decl(forOfSelfReferentialDottedName.ts, 2, 10))
+>a : Symbol(a, Decl(forOfSelfReferentialDottedName.ts, 2, 10))
+
+    a();
+>a : Symbol(a, Decl(forOfSelfReferentialDottedName.ts, 2, 10))
+
+    a;
+>a : Symbol(a, Decl(forOfSelfReferentialDottedName.ts, 2, 10))
+}
+
diff --git a/testdata/baselines/reference/compiler/forOfSelfReferentialDottedName.types b/testdata/baselines/reference/compiler/forOfSelfReferentialDottedName.types
new file mode 100644
index 00000000000..d30d071f4fd
--- /dev/null
+++ b/testdata/baselines/reference/compiler/forOfSelfReferentialDottedName.types
@@ -0,0 +1,17 @@
+//// [tests/cases/compiler/forOfSelfReferentialDottedName.ts] ////
+
+=== forOfSelfReferentialDottedName.ts ===
+// A self-referential for-of iterable (`for (const a of a)`) plus a call and a
+// later narrowing reference must not infinitely recurse in getExplicitTypeOfSymbol.
+for (const a of a) {
+>a : any
+>a : any
+
+    a();
+>a() : any
+>a : any
+
+    a;
+>a : any
+}
+
diff --git a/testdata/tests/cases/compiler/forOfSelfReferentialDottedName.ts b/testdata/tests/cases/compiler/forOfSelfReferentialDottedName.ts
new file mode 100644
index 00000000000..3e85f1c0654
--- /dev/null
+++ b/testdata/tests/cases/compiler/forOfSelfReferentialDottedName.ts
@@ -0,0 +1,6 @@
+// A self-referential for-of iterable (`for (const a of a)`) plus a call and a
+// later narrowing reference must not infinitely recurse in getExplicitTypeOfSymbol.
+for (const a of a) {
+    a();
+    a;
+}