Reject exports from global augmentations

tsc/internal/checker/checker.go

@@ -5726,7 +5726,12 @@ func (c *Checker) checkExportSpecifier(node *ast.ExportSpecifierNode) {
 		}
 		// find immediate value referenced by exported name (SymbolFlags.Alias is set so we don't chase down aliases)
 		symbol := c.resolveName(exportedName, exportedName.Text(), ast.SymbolFlagsValue|ast.SymbolFlagsType|ast.SymbolFlagsNamespace|ast.SymbolFlagsAlias, nil /*nameNotFoundMessage*/, true /*isUse*/, false)
-		if symbol != nil && (symbol == c.undefinedSymbol || symbol == c.globalThisSymbol || symbol.Declarations != nil && ast.IsGlobalSourceFile(ast.GetDeclarationContainer(symbol.Declarations[0]))) {
+		isGlobalDeclaration := false
+		if symbol != nil && symbol.Declarations != nil {
+			declarationContainer := ast.GetDeclarationContainer(symbol.Declarations[0])
+			isGlobalDeclaration = ast.IsGlobalSourceFile(declarationContainer) || ast.IsModuleBlock(declarationContainer) && ast.IsGlobalScopeAugmentation(declarationContainer.Parent)
+		}
+		if symbol != nil && (symbol == c.undefinedSymbol || symbol == c.globalThisSymbol || isGlobalDeclaration) {
 			c.error(exportedName, diagnostics.Cannot_export_0_Only_local_declarations_can_be_exported_from_a_module, exportedName.Text())
 		} else {
 			c.markLinkedReferences(node, ReferenceHintExportSpecifier, nil /*propSymbol*/, nil /*parentType*/)

tsc/testdata/baselines/reference/compiler/exportSpecifierForAGlobalAugmentation.errors.txt

@@ -0,0 +1,12 @@
+exportSpecifierForAGlobalAugmentation.ts(5,10): error TS2661: Cannot export 'XYZ'. Only local declarations can be exported from a module.
+
+
+==== exportSpecifierForAGlobalAugmentation.ts (1 errors) ====
+    declare global {
+        var XYZ: number;
+    }
+
+    export { XYZ };
+             ~~~
+!!! error TS2661: Cannot export 'XYZ'. Only local declarations can be exported from a module.
+

tsc/testdata/baselines/reference/compiler/exportSpecifierForAGlobalAugmentation.js

@@ -0,0 +1,12 @@
+//// [tests/cases/compiler/exportSpecifierForAGlobalAugmentation.ts] ////
+
+//// [exportSpecifierForAGlobalAugmentation.ts]
+declare global {
+    var XYZ: number;
+}
+
+export { XYZ };
+
+
+//// [exportSpecifierForAGlobalAugmentation.js]
+export { XYZ };

tsc/testdata/baselines/reference/compiler/exportSpecifierForAGlobalAugmentation.symbols

@@ -0,0 +1,13 @@
+//// [tests/cases/compiler/exportSpecifierForAGlobalAugmentation.ts] ////
+
+=== exportSpecifierForAGlobalAugmentation.ts ===
+declare global {
+>global : Symbol(global, Decl(exportSpecifierForAGlobalAugmentation.ts, 0, 0))
+
+    var XYZ: number;
+>XYZ : Symbol(XYZ, Decl(exportSpecifierForAGlobalAugmentation.ts, 1, 7))
+}
+
+export { XYZ };
+>XYZ : Symbol(XYZ, Decl(exportSpecifierForAGlobalAugmentation.ts, 4, 8))
+

tsc/testdata/baselines/reference/compiler/exportSpecifierForAGlobalAugmentation.types

@@ -0,0 +1,13 @@
+//// [tests/cases/compiler/exportSpecifierForAGlobalAugmentation.ts] ////
+
+=== exportSpecifierForAGlobalAugmentation.ts ===
+declare global {
+>global : typeof global
+
+    var XYZ: number;
+>XYZ : number
+}
+
+export { XYZ };
+>XYZ : number
+

tsc/testdata/tests/cases/compiler/exportSpecifierForAGlobalAugmentation.ts

@@ -0,0 +1,5 @@
+declare global {
+    var XYZ: number;
+}
+
+export { XYZ };