Add depth limiter to isConstTypeVariable function

src/compiler/checker.ts

@@ -13719,6 +13719,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     result = computeBaseConstraint(getSimplifiedType(t, /*writing*/ false));
                     stack.pop();
                 }
+                else {
+                    result = circularConstraintType;
+                }
                 if (!popTypeResolution()) {
                     if (t.flags & TypeFlags.TypeParameter) {
                         const errorNode = getConstraintDeclaration(t as TypeParameter);

tests/baselines/reference/circularBaseConstraint.errors.txt

@@ -0,0 +1,22 @@
+tests/cases/compiler/circularBaseConstraint.ts(14,8): error TS2304: Cannot find name 'a'.
+
+
+==== tests/cases/compiler/circularBaseConstraint.ts (1 errors) ====
+    // Repro from #54610
+
+    type A<T> = T;
+
+    type B<T> = T extends any[]
+        ? never
+        : A<T> extends infer key
+        ? key extends keyof T
+            ? B<T[key]>
+            : never
+        : never;
+
+    function foo<T>() {
+        `${a}` as B<T>;
+           ~
+!!! error TS2304: Cannot find name 'a'.
+    }
+

tests/baselines/reference/circularBaseConstraint.symbols

@@ -0,0 +1,40 @@
+=== tests/cases/compiler/circularBaseConstraint.ts ===
+// Repro from #54610
+
+type A<T> = T;
+>A : Symbol(A, Decl(circularBaseConstraint.ts, 0, 0))
+>T : Symbol(T, Decl(circularBaseConstraint.ts, 2, 7))
+>T : Symbol(T, Decl(circularBaseConstraint.ts, 2, 7))
+
+type B<T> = T extends any[]
+>B : Symbol(B, Decl(circularBaseConstraint.ts, 2, 14))
+>T : Symbol(T, Decl(circularBaseConstraint.ts, 4, 7))
+>T : Symbol(T, Decl(circularBaseConstraint.ts, 4, 7))
+
+    ? never
+    : A<T> extends infer key
+>A : Symbol(A, Decl(circularBaseConstraint.ts, 0, 0))
+>T : Symbol(T, Decl(circularBaseConstraint.ts, 4, 7))
+>key : Symbol(key, Decl(circularBaseConstraint.ts, 6, 24))
+
+    ? key extends keyof T
+>key : Symbol(key, Decl(circularBaseConstraint.ts, 6, 24))
+>T : Symbol(T, Decl(circularBaseConstraint.ts, 4, 7))
+
+        ? B<T[key]>
+>B : Symbol(B, Decl(circularBaseConstraint.ts, 2, 14))
+>T : Symbol(T, Decl(circularBaseConstraint.ts, 4, 7))
+>key : Symbol(key, Decl(circularBaseConstraint.ts, 6, 24))
+
+        : never
+    : never;
+
+function foo<T>() {
+>foo : Symbol(foo, Decl(circularBaseConstraint.ts, 10, 12))
+>T : Symbol(T, Decl(circularBaseConstraint.ts, 12, 13))
+
+    `${a}` as B<T>;
+>B : Symbol(B, Decl(circularBaseConstraint.ts, 2, 14))
+>T : Symbol(T, Decl(circularBaseConstraint.ts, 12, 13))
+}
+

tests/baselines/reference/circularBaseConstraint.types

@@ -0,0 +1,25 @@
+=== tests/cases/compiler/circularBaseConstraint.ts ===
+// Repro from #54610
+
+type A<T> = T;
+>A : T
+
+type B<T> = T extends any[]
+>B : B<T>
+
+    ? never
+    : A<T> extends infer key
+    ? key extends keyof T
+        ? B<T[key]>
+        : never
+    : never;
+
+function foo<T>() {
+>foo : <T>() => void
+
+    `${a}` as B<T>;
+>`${a}` as B<T> : B<T>
+>`${a}` : string
+>a : any
+}
+

tests/cases/compiler/circularBaseConstraint.ts

@@ -0,0 +1,18 @@
+// @strict: true
+// @noEmit: true
+
+// Repro from #54610
+
+type A<T> = T;
+
+type B<T> = T extends any[]
+    ? never
+    : A<T> extends infer key
+    ? key extends keyof T
+        ? B<T[key]>
+        : never
+    : never;
+
+function foo<T>() {
+    `${a}` as B<T>;
+}