Improve the highlight range for argument_must_be_a_constant

Change-Id: I70b31b8b710d753c3617d36ebfd894fa0a4d9b12
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/206441
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
diff --git a/pkg/analyzer/lib/src/generated/ffi_verifier.dart b/pkg/analyzer/lib/src/generated/ffi_verifier.dart
index a71cbce..8382b13 100644
--- a/pkg/analyzer/lib/src/generated/ffi_verifier.dart
+++ b/pkg/analyzer/lib/src/generated/ffi_verifier.dart
@@ -750,10 +750,9 @@
         if (arg is NamedExpression) {
           if (arg.element?.name == _isLeafParamName) {
             if (_maybeGetBoolConstValue(arg.expression) == null) {
-              final AstNode errorNode = node;
               _errorReporter.reportErrorForNode(
                   FfiCode.ARGUMENT_MUST_BE_A_CONSTANT,
-                  errorNode,
+                  arg.expression,
                   [_isLeafParamName]);
             }
           }
diff --git a/pkg/analyzer/test/src/diagnostics/argument_must_be_a_constant_test.dart b/pkg/analyzer/test/src/diagnostics/argument_must_be_a_constant_test.dart
index a60b375..8db3c12 100644
--- a/pkg/analyzer/test/src/diagnostics/argument_must_be_a_constant_test.dart
+++ b/pkg/analyzer/test/src/diagnostics/argument_must_be_a_constant_test.dart
@@ -27,7 +27,7 @@
   f(8);
 }
 ''', [
-      error(FfiCode.ARGUMENT_MUST_BE_A_CONSTANT, 211, 27),
+      error(FfiCode.ARGUMENT_MUST_BE_A_CONSTANT, 231, 6),
     ]);
   }
 
@@ -43,7 +43,7 @@
   f(8);
 }
 ''', [
-      error(FfiCode.ARGUMENT_MUST_BE_A_CONSTANT, 213, 27),
+      error(FfiCode.ARGUMENT_MUST_BE_A_CONSTANT, 233, 6),
     ]);
   }
 
@@ -58,7 +58,7 @@
   f(8);
 }
 ''', [
-      error(FfiCode.ARGUMENT_MUST_BE_A_CONSTANT, 201, 27),
+      error(FfiCode.ARGUMENT_MUST_BE_A_CONSTANT, 221, 6),
     ]);
   }
 
@@ -72,7 +72,7 @@
   l.lookupFunction<Int8UnOp, IntUnOp>("timesFour", isLeaf:isLeaf);
 }
 ''', [
-      error(FfiCode.ARGUMENT_MUST_BE_A_CONSTANT, 174, 63),
+      error(FfiCode.ARGUMENT_MUST_BE_A_CONSTANT, 230, 6),
     ]);
   }
 }