Fix cross-module generic function export and add coverage

tslang/lib/TypeScript/MLIRGenFunctions.cpp

@@ -344,9 +344,32 @@ namespace mlirgen
             funcProto->setHasExtraFields(existLocalVarsInThisContextMap(funcProto->getName()));
         }
 
+        // a concrete instantiation of a generic function (e.g. identity<number>) reprocesses
+        // the SAME AST node as the bare template (`export function identity<T>(...)`), so
+        // processFunctionAttributes's own getExportModifier check below would otherwise mark
+        // this LOCAL, per-instantiation specialization as exported too - wrong for the same
+        // two reasons the class-generic fix (class-generic-declaration-export-fix) suppresses
+        // isExport on a specialized ClassInfo: (1) a specialization materialized by whichever
+        // module instantiates it is local to that module, not a re-export of it (the bare
+        // template's own export is handled separately via registerGenericFunctionLike /
+        // addGenericFunctionDeclarationToExport); (2) a multi-type-param instantiation's
+        // mangled name contains a raw comma (e.g. M.pair<!ts.number,!ts.string>), a
+        // metacharacter in the linker's `/EXPORT:name[,option]` directive syntax - lld rejects
+        // it outright ("invalid /export:"). NOTE: can't key this off
+        // genContext.instantiateSpecializedFunction - mlirGenFunctionLikeDeclaration
+        // deliberately clears that flag on funcDeclGenContext before calling
+        // mlirGenFunctionPrototype (to stop nested generics being instantiated by mistake),
+        // so by the time we get here it always reads false. typeParamsWithArgs is the
+        // signal that actually survives - same one the class fix uses. Must be passed INTO
+        // processFunctionAttributes (not applied to its return value afterward) because it
+        // pushes the "export" attribute into `attrs` itself before returning.
+        auto suppressExportForGenericInstantiation =
+            functionLikeDeclarationBaseAST->typeParameters.size() > 0 && !genContext.typeParamsWithArgs.empty();
+
         SmallVector<mlir::NamedAttribute> attrs;
-        auto dllExport = processFunctionAttributes(location, fullName, functionLikeDeclarationBaseAST, attrs, funcProtoGenContext);
-
+        auto dllExport = processFunctionAttributes(location, fullName, functionLikeDeclarationBaseAST, attrs, funcProtoGenContext,
+            suppressExportForGenericInstantiation);
+
         if (funcType)
         {
             auto it = getCaptureVarsMap().find(funcProto->getName());

tslang/lib/TypeScript/MLIRGenImpl.h

@@ -1778,7 +1778,8 @@ class MLIRGenImpl
     }
 
     bool processFunctionAttributes(mlir::Location location, StringRef fullName,
-        FunctionLikeDeclarationBase functionLikeDeclarationBaseAST, SmallVector<mlir::NamedAttribute> &attrs, const GenContext &genContext)
+        FunctionLikeDeclarationBase functionLikeDeclarationBaseAST, SmallVector<mlir::NamedAttribute> &attrs, const GenContext &genContext,
+        bool suppressExport = false)
     {
 #ifdef ADD_GC_ATTRIBUTE
         attrs.push_back({builder.getIdentifier(TS_GC_ATTRIBUTE), mlir::UnitAttr::get(builder.getContext())});
@@ -1802,8 +1803,9 @@ class MLIRGenImpl
         });
 
         // add modifiers
-        auto dllExport = getExportModifier(functionLikeDeclarationBaseAST)
-            || ((functionLikeDeclarationBaseAST->internalFlags & InternalFlags::DllExport) == InternalFlags::DllExport);
+        auto dllExport = !suppressExport
+            && (getExportModifier(functionLikeDeclarationBaseAST)
+                || ((functionLikeDeclarationBaseAST->internalFlags & InternalFlags::DllExport) == InternalFlags::DllExport));
         if (dllExport)
         {
             attrs.push_back({mlir::StringAttr::get(builder.getContext(), "export"), mlir::UnitAttr::get(builder.getContext())});
@@ -1861,6 +1863,17 @@ class MLIRGenImpl
 
         if (existGenericFunctionMap(name))
         {
+            // already registered - but the registration itself typically happens during
+            // Stages::Discovering (before addGenericFunctionDeclarationToExport's
+            // isAddedToExport gate, which only actually emits once stage ==
+            // Stages::SourceGeneration, will do anything) - retry the export step alone
+            // using the existing GenericFunctionInfo rather than skipping it entirely.
+            // Mirrors registerGenericClass's identical gotcha-3 fix.
+            if (getExportModifier(functionLikeDeclarationBaseAST))
+            {
+                addGenericFunctionDeclarationToExport(lookupGenericFunctionMap(name));
+            }
+
             return {mlir::success(), name};
         }
 
@@ -1909,6 +1922,18 @@ class MLIRGenImpl
         getGenericFunctionMap().insert({namePtr, newGenericFunctionPtr});
         fullNameGenericFunctionsMap.insert(fullNamePtr, newGenericFunctionPtr);
 
+        // support dynamic loading: a generic function is never instantiated in this
+        // module if nothing here uses it concretely, so mlirGenFunctionPrototype's own
+        // addFunctionDeclarationToExport call never runs for the bare template (it only
+        // fires for a SPECIALIZED instantiation) - the bare template needs to be
+        // exported here instead, the one place every generic function declaration
+        // passes through regardless of whether it is ever instantiated locally. Mirrors
+        // registerGenericClass.
+        if (getExportModifier(functionLikeDeclarationBaseAST))
+        {
+            addGenericFunctionDeclarationToExport(newGenericFunctionPtr);
+        }
+
         return {mlir::success(), name};
     }
 
@@ -10322,6 +10347,52 @@ class MLIRGenImpl
         declExports << ss.str().str();
     }
 
+    void addGenericFunctionDeclarationToExport(GenericFunctionInfo::TypePtr genericFunctionInfo)
+    {
+        // funcType can be null when registered with ignoreFunctionArgsDetection=true
+        // (see registerGenericFunctionLike) - nothing to key isAddedToExport's dedup on
+        // in that case, so just fall through and re-print (matches
+        // addFunctionDeclarationToExport's own "TODO: add distinct declaration" gap for
+        // the non-generic case).
+        if (genericFunctionInfo->funcType && isAddedToExport(genericFunctionInfo->funcType))
+        {
+            // already added
+            return;
+        }
+
+        // same bounds-check as addGenericClassDeclarationToExport - a generic function
+        // re-declared while re-importing another module's embedded declarations still
+        // carries its own `export` keyword verbatim, but at that point `sourceFile` is
+        // the ambient/outer file, not the "partial" buffer parsePartialStatements
+        // actually parsed this declaration from.
+        auto declEnd = static_cast<size_t>(genericFunctionInfo->functionDeclaration->_end);
+        if (declEnd > genericFunctionInfo->sourceFile->text.length())
+        {
+            return;
+        }
+
+        if (genericFunctionInfo->funcType)
+        {
+            exportedTypes.insert(genericFunctionInfo->funcType);
+        }
+
+        // like a generic class, a generic function has no compiled body for any given
+        // instantiation: each importing module instantiates it locally, on demand,
+        // exactly like a same-file usage would. So the FULL original source - type
+        // parameters and body intact, no @dllimport marker - must be re-exported
+        // verbatim for parsePartialStatements to recompile per instantiation in the
+        // importer.
+        auto declText = convertWideToUTF8(getTextOfNodeFromSourceText(
+            genericFunctionInfo->sourceFile->text, genericFunctionInfo->functionDeclaration.as<Node>(), true));
+
+        SmallVector<char> out;
+        llvm::raw_svector_ostream ss(out);
+        MLIRDeclarationPrinter dp(ss);
+        dp.printGenericClass(genericFunctionInfo->elementNamespace, declText);
+
+        genericDeclExports << ss.str().str();
+    }
+
     void addGenericClassDeclarationToExport(GenericClassInfo::TypePtr genericClassInfo)
     {
         if (isAddedToExport(genericClassInfo->classType))

tslang/test/tester/CMakeLists.txt

@@ -884,6 +884,7 @@ add_test(NAME test-compile-export-import-class-static COMMAND test-runner "${PRO
 #     declaration's own re-export attempt hit a stale source-file/AST-position mismatch).
 # See class-generic-declaration-export-fix memory for the full account.
 add_test(NAME test-compile-export-import-class-generic COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_generic.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_generic.ts")
+add_test(NAME test-compile-export-import-function-generic COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/import_function_generic.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_function_generic.ts")
 add_test(NAME test-compile-export-import-class-accessor COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_accessor.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_accessor.ts")
 add_test(NAME test-compile-export-import-class-indexer COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_indexer.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_indexer.ts")
 add_test(NAME test-compile-export-import-interface-indexer COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/import_interface_indexer.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_interface_indexer.ts")
@@ -955,6 +956,7 @@ add_test(NAME test-compile-shared-export-import-class-structural-interface COMMA
 # add_test(NAME test-compile-shared-export-import-class-implements-interface-abstract COMMAND test-runner -shared "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_implements_interface_abstract.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_implements_interface_abstract.ts")
 # FIXED: see the matching test-compile-export-import-class-generic comment above (2026-07-22).
 add_test(NAME test-compile-shared-export-import-class-generic COMMAND test-runner -shared "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_generic.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_generic.ts")
+add_test(NAME test-compile-shared-export-import-function-generic COMMAND test-runner -shared "${PROJECT_SOURCE_DIR}/test/tester/tests/import_function_generic.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_function_generic.ts")
 # FIXED (2026-07-22): the -shared declaration-reconstruction path never printed real
 # get/set syntax for a class's accessors, only the underlying get_x/set_x funcOps as
 # ordinary methods - so property-style access ("Class member 'celsius' can't be found")
@@ -1001,6 +1003,7 @@ add_test(NAME test-jit-shared-export-import-class-structural-interface COMMAND t
 # add_test(NAME test-jit-shared-export-import-class-implements-interface-abstract COMMAND test-runner -jit -shared "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_implements_interface_abstract.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_implements_interface_abstract.ts")
 # FIXED: see the matching test-compile-export-import-class-generic comment above (2026-07-22).
 add_test(NAME test-jit-shared-export-import-class-generic COMMAND test-runner -jit -shared "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_generic.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_generic.ts")
+add_test(NAME test-jit-shared-export-import-function-generic COMMAND test-runner -jit -shared "${PROJECT_SOURCE_DIR}/test/tester/tests/import_function_generic.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_function_generic.ts")
 # FIXED: see the matching test-compile-shared-export-import-class-accessor comment above (2026-07-22).
 add_test(NAME test-jit-shared-export-import-class-accessor COMMAND test-runner -jit -shared "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_accessor.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_accessor.ts")
 add_test(NAME test-jit-shared-export-import-class-indexer COMMAND test-runner -jit -shared "${PROJECT_SOURCE_DIR}/test/tester/tests/import_class_indexer.ts" "${PROJECT_SOURCE_DIR}/test/tester/tests/export_class_indexer.ts")

tslang/test/tester/tests/export_function_generic.ts

@@ -0,0 +1,18 @@
+namespace M {
+
+    // Cross-module counterpart to 00funcs_generic.ts. GenericFunctionInfo
+    // (MLIRGenStore.h) is structurally analogous to GenericClassInfo, whose
+    // cross-module export gap took 4 fixes to close (PR #280,
+    // class-generic-declaration-export-fix) - per
+    // decls-cross-module-declaration-mechanism memory, generic
+    // functions/interfaces/type-aliases were flagged as plausible,
+    // unverified instances of the exact same gap.
+
+    export function identity<T>(x: T): T {
+        return x;
+    }
+
+    export function pair<A, B>(a: A, b: B): string {
+        return `${a}-${b}`;
+    }
+}

tslang/test/tester/tests/import_function_generic.ts

@@ -0,0 +1,9 @@
+import './export_function_generic'
+
+function main() {
+    assert(M.identity<number>(42) == 42);
+    assert(M.identity<string>("hi") == "hi");
+    assert(M.pair<number, string>(1, "one") == "1-one");
+
+    print("done.");
+}