Fix https://github.com/DefinitelyTyped/DefinitelyTyped/issues/14036:

Remove assert.

src/compiler/checker.ts

@@ -4172,7 +4172,6 @@ namespace ts {
         }
 
         function getDeclaredTypeOfSymbol(symbol: Symbol): Type {
-            Debug.assert((symbol.flags & SymbolFlags.Instantiated) === 0);
             if (symbol.flags & (SymbolFlags.Class | SymbolFlags.Interface)) {
                 return getDeclaredTypeOfClassOrInterface(symbol);
             }

tests/baselines/reference/mergedDeclarations7.errors.txt

@@ -0,0 +1,32 @@
+tests/cases/compiler/test.ts(4,5): error TS2322: Type 'PassportStatic' is not assignable to type 'Passport'.
+  Types of property 'use' are incompatible.
+    Type '() => PassportStatic' is not assignable to type '() => this'.
+      Type 'PassportStatic' is not assignable to type 'this'.
+
+
+==== tests/cases/compiler/passport.d.ts (0 errors) ====
+    declare module 'passport' {
+        namespace passport {
+            interface Passport {
+                use(): this;
+            }
+    
+            interface PassportStatic extends Passport {
+                Passport: {new(): Passport};
+            }
+        }
+    
+        const passport: passport.PassportStatic;
+        export = passport;
+    }
+    
+==== tests/cases/compiler/test.ts (1 errors) ====
+    import * as passport from "passport";
+    import { Passport } from "passport";
+    
+    let p: Passport = passport.use();
+        ~
+!!! error TS2322: Type 'PassportStatic' is not assignable to type 'Passport'.
+!!! error TS2322:   Types of property 'use' are incompatible.
+!!! error TS2322:     Type '() => PassportStatic' is not assignable to type '() => this'.
+!!! error TS2322:       Type 'PassportStatic' is not assignable to type 'this'.

tests/baselines/reference/mergedDeclarations7.js

@@ -0,0 +1,28 @@
+//// [tests/cases/compiler/mergedDeclarations7.ts] ////
+
+//// [passport.d.ts]
+declare module 'passport' {
+    namespace passport {
+        interface Passport {
+            use(): this;
+        }
+
+        interface PassportStatic extends Passport {
+            Passport: {new(): Passport};
+        }
+    }
+
+    const passport: passport.PassportStatic;
+    export = passport;
+}
+
+//// [test.ts]
+import * as passport from "passport";
+import { Passport } from "passport";
+
+let p: Passport = passport.use();
+
+//// [test.js]
+"use strict";
+var passport = require("passport");
+var p = passport.use();

tests/cases/compiler/mergedDeclarations7.ts

@@ -0,0 +1,21 @@
+// @filename: passport.d.ts
+declare module 'passport' {
+    namespace passport {
+        interface Passport {
+            use(): this;
+        }
+
+        interface PassportStatic extends Passport {
+            Passport: {new(): Passport};
+        }
+    }
+
+    const passport: passport.PassportStatic;
+    export = passport;
+}
+
+//@filename: test.ts
+import * as passport from "passport";
+import { Passport } from "passport";
+
+let p: Passport = passport.use();