fix exceptions when completing other edge cases

pkg/analysis_server/test/services/completion/optype_test.dart

Index: pkg/analysis_server/test/services/completion/optype_test.dart
diff --git a/pkg/analysis_server/test/services/completion/optype_test.dart b/pkg/analysis_server/test/services/completion/optype_test.dart
index b8dfadbbbdbb9a9413befad947f4a618b00a9e97..a2634b1da84f1455fd080fd2b3c06678d6a03d9d 100644
--- a/pkg/analysis_server/test/services/completion/optype_test.dart
+++ b/pkg/analysis_server/test/services/completion/optype_test.dart
@@ -663,6 +663,12 @@ class OpTypeTest {
     assertOpType();
   }
 
+  test_FunctionExpressionInvocation() {
+    // ArgumentList  FunctionExpressionInvocation  ExpressionStatement
+    addTestSource('main() { ((x) => x + 7)^(2) }');
+    assertOpType();
+  }
+
   test_FunctionTypeAlias() {
     // SimpleIdentifier  FunctionTypeAlias  CompilationUnit
     addTestSource('typedef n^ ;');
@@ -988,6 +994,12 @@ class C2 {
     assertOpType(invocation: true);
   }
 
+  test_PostfixExpression() {
+    // SimpleIdentifier  PostfixExpression  ForStatement
+    addTestSource('int x = 0; main() {ax+^+;}');
+    assertOpType(returnValue: true, typeNames: true);
+  }
+
   test_PrefixedIdentifier_class_const() {
     // SimpleIdentifier PrefixedIdentifier ExpressionStatement Block
     addTestSource('main() {A.^}');
@@ -1062,6 +1074,12 @@ class C2 {
     assertOpType(invocation: true);
   }
 
+  test_ThrowExpression() {
+    // SimpleIdentifier  ThrowExpression  ExpressionStatement
+    addTestSource('main() {throw ^;}');
+    assertOpType(returnValue: true, typeNames: true);
+  }
+
   test_TopLevelVariableDeclaration_typed_name() {
     // SimpleIdentifier  VariableDeclaration  VariableDeclarationList
     // TopLevelVariableDeclaration