[analyzer] Fix exception searching synthetic parameters

This fixes #60005 caused by `source!` by instead handling the null. However, it leaves navigation still not-working for these synthetic parameters (see failing tests).

Change-Id: I793130a9533ccf97b523a50d74375ebf6dead7e3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/411600
Reviewed-by: Konstantin Shcheglov <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>

Author: DanTup

pkg/analysis_server/test/analysis/get_navigation_test.dart

@@ -466,6 +466,25 @@ void f(A a) {
     }
   }
 
+  @FailingTest(issue: 'https://github.com/dart-lang/sdk/issues/60200')
+  Future<void> test_parameter_generic() async {
+    addTestFile('''
+void f() {
+  B().m(p: null);
+}
+
+class A<T> {
+  void m({T? p}) {}
+}
+
+class B extends A<String> {}
+''');
+    await waitForTasksFinished();
+    await _getNavigation(search: 'p: null');
+    assertHasRegion('p: null');
+    assertHasTarget('p}) {}');
+  }
+
   Future<void> test_parameter_wildcard() async {
     addTestFile('''
 var _ = 0;

pkg/analysis_server/test/search/element_references_test.dart

@@ -998,6 +998,47 @@ void f(ppp) {
     assertHasResult(SearchResultKind.READ, 'ppp();');
   }
 
+  Future<void> test_parameter_generic_declaration() async {
+    addTestFile('''
+void f() {
+  B().m(p: null); // 1
+  B().m(p: null); // 2
+}
+
+class A<T> {
+  void m({T? p}) {} // 3
+}
+
+class B extends A<String> {}
+''');
+    await findElementReferences(search: 'p}) {} // 3', false);
+    expect(searchElement!.kind, ElementKind.PARAMETER);
+    expect(results, hasLength(2));
+    assertHasResult(SearchResultKind.REFERENCE, 'p: null); // 1');
+    assertHasResult(SearchResultKind.REFERENCE, 'p: null); // 2');
+  }
+
+  @FailingTest(issue: 'https://github.com/dart-lang/sdk/issues/60200')
+  Future<void> test_parameter_generic_invocation() async {
+    addTestFile('''
+void f() {
+  B().m(p: null); // 1
+  B().m(p: null); // 2
+}
+
+class A<T> {
+  void m({T? p}) {} // 3
+}
+
+class B extends A<String> {}
+''');
+    await findElementReferences(search: 'p: null); // 1', false);
+    expect(searchElement!.kind, ElementKind.PARAMETER);
+    expect(results, hasLength(2));
+    assertHasResult(SearchResultKind.REFERENCE, 'p: null); // 1');
+    assertHasResult(SearchResultKind.REFERENCE, 'p: null); // 2');
+  }
+
   @failingTest
   Future<void> test_path_inConstructor_named() async {
     // The path does not contain the first expected element.

pkg/analyzer/lib/src/dart/analysis/search.dart

@@ -632,7 +632,11 @@ class Search {
       name = externalElement.enclosingElement2.displayName;
     }
 
-    var elementPath = element.firstFragment.libraryFragment!.source.fullName;
+    var elementPath = element.firstFragment.libraryFragment?.source.fullName;
+    if (elementPath == null) {
+      return;
+    }
+
     var elementFile = _driver.fsState.getExistingFromPath(elementPath);
     if (elementFile == null) {
       return;
@@ -896,8 +900,8 @@ class Search {
     bool Function(AstNode n) isRootNode,
     SearchedFiles searchedFiles,
   ) async {
-    String path = element.firstFragment.libraryFragment!.source.fullName;
-    if (!searchedFiles.add(path, this)) {
+    String? path = element.firstFragment.libraryFragment?.source.fullName;
+    if (path == null || !searchedFiles.add(path, this)) {
       return const <SearchResult>[];
     }
 

pkg/analyzer/lib/src/dart/element/element.dart

@@ -3418,6 +3418,9 @@ class FormalParameterFragmentImpl extends VariableFragmentImpl
     TypeImpl type,
     ParameterKind parameterKind,
   ) {
+    // TODO(dantup): This does not keep any reference to the non-synthetic
+    //  parameter which prevents navigation/references from working. See
+    //  https://github.com/dart-lang/sdk/issues/60200
     var element = FormalParameterFragmentImpl(
       name: name2 ?? '',
       nameOffset: -1,

pkg/analyzer/test/src/dart/analysis/search_test.dart

@@ -2111,6 +2111,78 @@ main(A<int> a) {
 ''');
   }
 
+  test_searchReferences_ParameterElement_generic_atDeclaration() async {
+    await resolveTestCode('''
+void f() {
+  B().m(p: null); // 1
+  B().m(p: null); // 2
+}
+
+class A<T> {
+  void m({T? p}) {} // 3
+}
+
+class B extends A<String> {}
+''');
+    var element = findElement2.parameter('p');
+    await assertElementReferencesText(element, r'''
+<testLibraryFragment>::@function::f
+  19 2:9 |p| REFERENCE qualified
+  42 3:9 |p| REFERENCE qualified
+''');
+  }
+
+  @FailingTest(
+      // When this test begins passing, the temporary test
+      // test_searchReferences_ParameterElement_generic_atInvocation_doesNotThrow_issue60005
+      // can be removed.
+      issue: 'https://github.com/dart-lang/sdk/issues/60200')
+  test_searchReferences_ParameterElement_generic_atInvocation() async {
+    await resolveTestCode('''
+void f() {
+  B().m(p: null); // 1
+  B().m(p: null); // 2
+}
+
+class A<T> {
+  void m({T? p}) {} // 3
+}
+
+class B extends A<String> {}
+''');
+    var element =
+        findNode.namedExpression('p: null); // 1').correspondingParameter!;
+    await assertElementReferencesText(element, r'''
+<testLibraryFragment>::@function::f
+  19 2:9 |p| REFERENCE qualified
+  42 3:9 |p| REFERENCE qualified
+''');
+  }
+
+  /// A temporary test to ensure the search does not throw, while
+  /// [test_searchReferences_ParameterElement_generic_atInvocation] is marked as
+  /// failing.
+  ///
+  /// This test can be removed once [test_searchReferences_ParameterElement_generic_atInvocation]
+  /// is passing.
+  test_searchReferences_ParameterElement_generic_atInvocation_doesNotThrow_issue60005() async {
+    await resolveTestCode('''
+void f() {
+  B().m(p: null); // 1
+  B().m(p: null); // 2
+}
+
+class A<T> {
+  void m({T? p}) {} // 3
+}
+
+class B extends A<String> {}
+''');
+    var element =
+        findNode.namedExpression('p: null); // 1').correspondingParameter!;
+    expect(driver.search.references(element, SearchedFiles()), completes);
+  }
+
   test_searchReferences_ParameterElement_ofConstructor_super_named() async {
     await resolveTestCode('''
 class A {