Only suggest non-void members in string interpolations

Bug: https://github.com/dart-lang/sdk/issues/54682
Change-Id: I03a7fc0dc6f914b65775c84124b963929a9813bd
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/347980
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Auto-Submit: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Samuel Rawlins <srawlins@google.com>

pkg/analysis_server/lib/src/services/completion/dart/in_scope_completion_pass.dart

@@ -1229,7 +1229,7 @@ class InScopeCompletionPass extends SimpleAstVisitor<void> {
 
   @override
   void visitInterpolationExpression(InterpolationExpression node) {
-    declarationHelper(mustBeStatic: node.inStaticContext)
+    declarationHelper(mustBeStatic: node.inStaticContext, mustBeNonVoid: true)
         .addLexicalDeclarations(node);
   }
 

pkg/analysis_server/test/services/completion/dart/location/string_literal_test.dart

@@ -8,10 +8,30 @@ import '../../../../client/completion_driver_test.dart';
 
 void main() {
   defineReflectiveSuite(() {
+    defineReflectiveTests(StringInterpolationTest);
     defineReflectiveTests(StringLiteralTest);
   });
 }
 
+@reflectiveTest
+class StringInterpolationTest extends AbstractCompletionDriverTest
+    with StringInterpolationTestCases {}
+
+mixin StringInterpolationTestCases on AbstractCompletionDriverTest {
+  Future<void> test_inBraces_nonVoid() async {
+    await computeSuggestions(r'''
+var s = 'a ${^} b';
+void f0() {}
+int f1() {}
+''');
+    assertResponse(r'''
+suggestions
+  f1
+    kind: functionInvocation
+''');
+  }
+}
+
 @reflectiveTest
 class StringLiteralTest extends AbstractCompletionDriverTest
     with StringLiteralTestCases {}