Add a test for adding new functions and types in the expression evaluator (NFC)

Author: adrian-prantl

lldb/source/Plugins/ExpressionParser/Swift/SwiftExpressionParser.cpp

@@ -1835,6 +1835,7 @@ SwiftExpressionParser::Parse(DiagnosticManager &diagnostic_manager,
           new SwiftASTManipulatorBase::VariableMetadataPersistent(
               persistent_variable));
 
+      // This is only exercised by the PlaygroundsREPL tests.
       persistent_state->RegisterSwiftPersistentDecl(decl);
     }
 

lldb/test/API/lang/swift/expression/function_definition/Makefile

@@ -0,0 +1,2 @@
+SWIFT_SOURCES := main.swift
+include Makefile.rules

lldb/test/API/lang/swift/expression/function_definition/TestSwiftFunctionDefinition.py

@@ -0,0 +1,16 @@
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+import lldbsuite.test.lldbutil as lldbutil
+
+
+class TestSwiftFunctionDefinition(TestBase):
+    NO_DEBUG_INFO_TESTCASE = True
+    @swiftTest
+    def test(self):
+        """Test that persistent variables are mutable."""
+        self.build()
+        lldbutil.run_to_name_breakpoint(self, "main")
+        self.expect("expr struct $S { let v : Int }")
+        self.expect("expr func $dup<T>(_ t: T) -> (T, T) { return (t, t) }")
+        self.expect("expr $dup($S(v: 1))", substrs=["($S, $S)", "v = 1", "v = 1"])

lldb/test/API/lang/swift/expression/function_definition/main.swift

@@ -0,0 +1 @@
+// does nothing