Fix out of range return value of get list item instruction

Author: adazem009

src/engine/internal/llvm/instructions/lists.cpp

@@ -246,7 +246,7 @@ LLVMInstruction *Lists::buildGetListItem(LLVMInstruction *ins)
     llvm::Value *index = m_utils.castValue(arg.second, arg.first);
     llvm::Value *inRange = m_builder.CreateAnd(m_builder.CreateFCmpOGE(index, min), m_builder.CreateFCmpOLT(index, size));
 
-    LLVMConstantRegister nullReg(listType, Value());
+    LLVMConstantRegister nullReg(Compiler::StaticType::String, "");
     llvm::Value *null = m_utils.createValue(static_cast<LLVMRegister *>(&nullReg));
 
     index = m_builder.CreateFPToUI(index, m_builder.getInt64Ty());

src/engine/internal/llvm/llvmcodeanalyzer.cpp

@@ -100,7 +100,8 @@ void LLVMCodeAnalyzer::analyzeScript(const LLVMInstructionList &script) const
             updateListType(currentBranch, ins, typeAssignedInstructions, false);
 
             // Store the type in the return register
-            ins->functionReturnReg->setType(ins->targetType);
+            // NOTE: Get list item returns empty string if index is out of range
+            ins->functionReturnReg->setType(ins->targetType | Compiler::StaticType::String);
         }
 
         ins = ins->next;

test/blocks/list_blocks_test.cpp

@@ -422,14 +422,14 @@ TEST_F(ListBlocksTest, ItemOfList)
     static const std::string expected =
         "dolor\n"
         "true\n"
-        "0\n"
-        "0\n"
+        "\n"
+        "\n"
         "true\n"
         "123\n"
         "Lorem\n"
-        "0\n"
-        "0\n"
-        "0\n";
+        "\n"
+        "\n"
+        "\n";
 
     EXPECT_CALL(m_rng, randint(1, 5)).WillOnce(Return(4)).WillOnce(Return(1));
     testing::internal::CaptureStdout();

test/llvm/code_analyzer/list_type_analysis.cpp

@@ -1002,8 +1002,8 @@ TEST(LLVMCodeAnalyzer_ListTypeAnalysis, CrossListDependency_SingleType)
     // targetList first write has no previous type
     ASSERT_EQ(appendList1_1->targetType, Compiler::StaticType::Void);
 
-    // targetList second write has Number type
-    ASSERT_EQ(appendList1_2->targetType, Compiler::StaticType::Number);
+    // targetList second write has Number | String type (get list item can always return string)
+    ASSERT_EQ(appendList1_2->targetType, Compiler::StaticType::Number | Compiler::StaticType::String);
 }
 
 TEST(LLVMCodeAnalyzer_ListTypeAnalysis, CrossListDependency_MultipleTypes)
@@ -1063,8 +1063,8 @@ TEST(LLVMCodeAnalyzer_ListTypeAnalysis, CrossListDependency_MultipleTypes)
     // targetList first write has no previous type
     ASSERT_EQ(appendList3->targetType, Compiler::StaticType::Void);
 
-    // targetList second write has Number or Bool type
-    ASSERT_EQ(appendList4->targetType, Compiler::StaticType::Number | Compiler::StaticType::Bool);
+    // targetList second write has Number or Bool type + String (get list item can always return string)
+    ASSERT_EQ(appendList4->targetType, Compiler::StaticType::Unknown);
 }
 
 TEST(LLVMCodeAnalyzer_ListTypeAnalysis, ChainedAssignmentsInLoop)
@@ -1243,8 +1243,8 @@ TEST(LLVMCodeAnalyzer_ListTypeAnalysis, ListReadReturnRegType)
 
     analyzer.analyzeScript(list);
 
-    // sourceList read return register has Number type
-    ASSERT_EQ(sourceValue.type(), Compiler::StaticType::Number);
+    // sourceList read return register has Number | String type (get list item can always return string)
+    ASSERT_EQ(sourceValue.type(), Compiler::StaticType::Number | Compiler::StaticType::String);
 }
 
 TEST(LLVMCodeAnalyzer_ListTypeAnalysis, CrossListWriteArgType)
@@ -1285,6 +1285,6 @@ TEST(LLVMCodeAnalyzer_ListTypeAnalysis, CrossListWriteArgType)
 
     analyzer.analyzeScript(list);
 
-    // last write argument has Number type
-    ASSERT_EQ(appendList1_1->args.back().first, Compiler::StaticType::Number);
+    // last write argument has Number | String type (get list item can always return string)
+    ASSERT_EQ(appendList1_1->args.back().first, Compiler::StaticType::Number | Compiler::StaticType::String);
 }

test/llvm/code_analyzer/mixed_type_analysis.cpp

@@ -121,8 +121,8 @@ TEST(LLVMCodeAnalyzer_MixedTypeAnalysis, ListToVariable_SimpleTransfer)
     // Variable write should see Unknown (first write)
     ASSERT_EQ(writeVar->targetType, Compiler::StaticType::Unknown);
 
-    // Return register should have Bool type
-    ASSERT_EQ(readListReg.type(), Compiler::StaticType::Bool);
+    // Return register should have Bool | String type (get list item can always return string)
+    ASSERT_EQ(readListReg.type(), Compiler::StaticType::Bool | Compiler::StaticType::String);
 }
 
 TEST(LLVMCodeAnalyzer_MixedTypeAnalysis, CircularVarListDependency)
@@ -502,5 +502,5 @@ TEST(LLVMCodeAnalyzer_MixedTypeAnalysis, ComplexChain_VarToListToVar_TypePropaga
     ASSERT_EQ(appendList->targetType, Compiler::StaticType::Void);
     ASSERT_EQ(readList->targetType, Compiler::StaticType::Number);
     ASSERT_EQ(writeTargetVar->targetType, Compiler::StaticType::Unknown);
-    ASSERT_EQ(readListReg.type(), Compiler::StaticType::Number);
+    ASSERT_EQ(readListReg.type(), Compiler::StaticType::Number | Compiler::StaticType::String); // get list item can always return string
 }

test/llvm/llvmcodebuilder_test.cpp

@@ -1449,20 +1449,30 @@ TEST_F(LLVMCodeBuilderTest, GetListItem)
     v = builder->addListItem(localList3.get(), v);
     builder->addFunctionCall("test_print_number", Compiler::StaticType::Void, { Compiler::StaticType::Number }, { v });
 
+    // Establish number type
+    builder->createListClear(localList3.get());
+    builder->createListAppend(localList3.get(), builder->addConstValue(1.5));
+
+    // Out-of-range index should still return empty string
+    v = builder->addConstValue(2);
+    v = builder->addListItem(localList3.get(), v);
+    builder->addFunctionCall("test_print_string", Compiler::StaticType::Void, { Compiler::StaticType::String }, { v });
+
     static const std::string expected =
         "3\n"
         "1\n"
-        "0\n"
-        "0\n"
+        "\n"
+        "\n"
         "Lorem\n"
         "dolor\n"
         "sit\n"
+        "\n"
+        "\n"
         "0\n"
         "0\n"
         "0\n"
         "0\n"
-        "0\n"
-        "0\n";
+        "\n";
 
     auto code = builder->build();
     Script script(&sprite, nullptr, nullptr);
@@ -1477,7 +1487,7 @@ TEST_F(LLVMCodeBuilderTest, GetListItem)
     ASSERT_EQ(globalList->toString(), "1 test 3");
     ASSERT_EQ(localList1->toString(), "Lorem ipsum dolor sit");
     ASSERT_EQ(localList2->toString(), "-564.121 4257.4");
-    ASSERT_EQ(localList3->toString(), "true false");
+    ASSERT_EQ(localList3->toString(), "1.5");
 }
 
 TEST_F(LLVMCodeBuilderTest, GetListSize)