Fix crash when attempting to merge an import with a local declaration

src/compiler/checker.ts

@@ -19151,6 +19151,8 @@ namespace ts {
                             : DeclarationSpaces.ExportNamespace;
                     case SyntaxKind.ClassDeclaration:
                     case SyntaxKind.EnumDeclaration:
+                    // A NamespaceImport declares an Alias, which is allowed to merge with other values within the module
+                    case SyntaxKind.NamespaceImport:
                         return DeclarationSpaces.ExportType | DeclarationSpaces.ExportValue;
                     case SyntaxKind.ImportEqualsDeclaration:
                         let result = DeclarationSpaces.None;

tests/baselines/reference/noCrashOnImportShadowing.errors.txt

@@ -0,0 +1,33 @@
+tests/cases/compiler/index.ts(4,1): error TS2693: 'B' only refers to a type, but is being used as a value here.
+tests/cases/compiler/index.ts(9,10): error TS2304: Cannot find name 'OriginalB'.
+
+
+==== tests/cases/compiler/b.ts (0 errors) ====
+    export const zzz = 123;
+
+==== tests/cases/compiler/a.ts (0 errors) ====
+    import * as B from "./b";
+
+    interface B {
+        x: string;
+    }
+
+    const x: B = { x: "" };
+    B.zzz;
+
+    export { B };
+
+==== tests/cases/compiler/index.ts (2 errors) ====
+    import { B } from "./a";
+
+    const x: B = { x: "" };
+    B.zzz;
+    ~
+!!! error TS2693: 'B' only refers to a type, but is being used as a value here.
+
+    import * as OriginalB from "./b";
+    OriginalB.zzz;
+
+    const y: OriginalB = x;
+             ~~~~~~~~~
+!!! error TS2304: Cannot find name 'OriginalB'.

tests/baselines/reference/noCrashOnImportShadowing.js

@@ -0,0 +1,46 @@
+//// [tests/cases/compiler/noCrashOnImportShadowing.ts] ////
+
+//// [b.ts]
+export const zzz = 123;
+
+//// [a.ts]
+import * as B from "./b";
+
+interface B {
+    x: string;
+}
+
+const x: B = { x: "" };
+B.zzz;
+
+export { B };
+
+//// [index.ts]
+import { B } from "./a";
+
+const x: B = { x: "" };
+B.zzz;
+
+import * as OriginalB from "./b";
+OriginalB.zzz;
+
+const y: OriginalB = x;
+
+//// [b.js]
+"use strict";
+exports.__esModule = true;
+exports.zzz = 123;
+//// [a.js]
+"use strict";
+exports.__esModule = true;
+var B = require("./b");
+var x = { x: "" };
+B.zzz;
+//// [index.js]
+"use strict";
+exports.__esModule = true;
+var x = { x: "" };
+B.zzz;
+var OriginalB = require("./b");
+OriginalB.zzz;
+var y = x;

tests/cases/compiler/noCrashOnImportShadowing.ts

@@ -0,0 +1,25 @@
+// @filename: b.ts
+export const zzz = 123;
+
+// @filename: a.ts
+import * as B from "./b";
+
+interface B {
+    x: string;
+}
+
+const x: B = { x: "" };
+B.zzz;
+
+export { B };
+
+// @filename: index.ts
+import { B } from "./a";
+
+const x: B = { x: "" };
+B.zzz;
+
+import * as OriginalB from "./b";
+OriginalB.zzz;
+
+const y: OriginalB = x;