Inform getDeclarationSpaces about how an imported exportAssignment may merge (#23816)

src/compiler/checker.ts

@@ -21611,7 +21611,8 @@ namespace ts {
                 ExportType = 1 << 1,
                 ExportNamespace = 1 << 2,
             }
-            function getDeclarationSpaces(d: Declaration): DeclarationSpaces {
+            function getDeclarationSpaces(decl: Declaration): DeclarationSpaces {
+                let d = decl as Node;
                 switch (d.kind) {
                     case SyntaxKind.InterfaceDeclaration:
                     case SyntaxKind.TypeAliasDeclaration:
@@ -21627,6 +21628,13 @@ namespace ts {
                         return DeclarationSpaces.ExportType | DeclarationSpaces.ExportValue;
                     case SyntaxKind.SourceFile:
                         return DeclarationSpaces.ExportType | DeclarationSpaces.ExportValue | DeclarationSpaces.ExportNamespace;
+                    case SyntaxKind.ExportAssignment:
+                        // Export assigned entity name expressions act as aliases and should fall through, otherwise they export values
+                        if (!isEntityNameExpression((d as ExportAssignment).expression)) {
+                            return DeclarationSpaces.ExportValue;
+                        }
+                        d = (d as ExportAssignment).expression;
+                        /* falls through */
                     // The below options all declare an Alias, which is allowed to merge with other values within the importing module
                     case SyntaxKind.ImportEqualsDeclaration:
                     case SyntaxKind.NamespaceImport:

tests/baselines/reference/exportAssignmentImportMergeNoCrash.errors.txt

@@ -0,0 +1,24 @@
+tests/cases/compiler/user.ts(1,8): error TS2395: Individual declarations in merged declaration 'Obj' must be all exported or all local.
+tests/cases/compiler/user.ts(1,8): error TS2440: Import declaration conflicts with local declaration of 'Obj'.
+tests/cases/compiler/user.ts(3,14): error TS2395: Individual declarations in merged declaration 'Obj' must be all exported or all local.
+tests/cases/compiler/user.ts(3,25): error TS2448: Block-scoped variable 'Obj' used before its declaration.
+
+
+==== tests/cases/compiler/assignment.ts (0 errors) ====
+    export default {
+        foo: 12
+    };
+    
+==== tests/cases/compiler/user.ts (4 errors) ====
+    import Obj from "./assignment";
+           ~~~
+!!! error TS2395: Individual declarations in merged declaration 'Obj' must be all exported or all local.
+           ~~~
+!!! error TS2440: Import declaration conflicts with local declaration of 'Obj'.
+    
+    export const Obj = void Obj;
+                 ~~~
+!!! error TS2395: Individual declarations in merged declaration 'Obj' must be all exported or all local.
+                            ~~~
+!!! error TS2448: Block-scoped variable 'Obj' used before its declaration.
+    

tests/baselines/reference/exportAssignmentImportMergeNoCrash.js

@@ -0,0 +1,24 @@
+//// [tests/cases/compiler/exportAssignmentImportMergeNoCrash.ts] ////
+
+//// [assignment.ts]
+export default {
+    foo: 12
+};
+
+//// [user.ts]
+import Obj from "./assignment";
+
+export const Obj = void Obj;
+
+
+//// [assignment.js]
+"use strict";
+exports.__esModule = true;
+exports["default"] = {
+    foo: 12
+};
+//// [user.js]
+"use strict";
+exports.__esModule = true;
+var assignment_1 = require("./assignment");
+exports.Obj = void exports.Obj;

tests/baselines/reference/exportAssignmentImportMergeNoCrash.symbols

@@ -0,0 +1,15 @@
+=== tests/cases/compiler/assignment.ts ===
+export default {
+    foo: 12
+>foo : Symbol(foo, Decl(assignment.ts, 0, 16))
+
+};
+
+=== tests/cases/compiler/user.ts ===
+import Obj from "./assignment";
+>Obj : Symbol(Obj, Decl(user.ts, 0, 6), Decl(user.ts, 2, 12))
+
+export const Obj = void Obj;
+>Obj : Symbol(Obj, Decl(user.ts, 2, 12))
+>Obj : Symbol(Obj, Decl(user.ts, 0, 6), Decl(user.ts, 2, 12))
+

tests/baselines/reference/exportAssignmentImportMergeNoCrash.types

@@ -0,0 +1,19 @@
+=== tests/cases/compiler/assignment.ts ===
+export default {
+>{    foo: 12} : { foo: number; }
+
+    foo: 12
+>foo : number
+>12 : 12
+
+};
+
+=== tests/cases/compiler/user.ts ===
+import Obj from "./assignment";
+>Obj : { foo: number; }
+
+export const Obj = void Obj;
+>Obj : any
+>void Obj : undefined
+>Obj : any
+

tests/cases/compiler/exportAssignmentImportMergeNoCrash.ts

@@ -0,0 +1,9 @@
+// @filename: assignment.ts
+export default {
+    foo: 12
+};
+
+// @filename: user.ts
+import Obj from "./assignment";
+
+export const Obj = void Obj;