Class AssignIfUnsetAsmGenerator

java.lang.Object

org.ek9lang.compiler.backend.jvm.AbstractAsmGenerator

org.ek9lang.compiler.backend.jvm.AbstractControlFlowAsmGenerator

org.ek9lang.compiler.backend.jvm.AssignIfUnsetAsmGenerator

final class AssignIfUnsetAsmGenerator
extends AbstractControlFlowAsmGenerator

Specialized generator for EK9 assign-if-unset (:=?). Handles CONTROL_FLOW_CHAIN with chain_type: "ASSIGN_IF_UNSET".

EK9 Assign-If-Unset Pattern: variable :=? value

• Assigns value to variable only if variable is null or not set
• Prevents overwriting already-initialized variables
• Useful for default value initialization

Generates bytecode that checks if the target variable is unset (null or _isSet() false), and only performs the assignment if so. Follows the condition/branch/body pattern from AbstractControlFlowAsmGenerator.

Field Summary

Fields inherited from class AbstractControlFlowAsmGenerator

context

Fields inherited from class AbstractAsmGenerator

classWriter, constructTargetTuple, outputVisitor

Constructor Summary

Constructors

Constructor	Description
AssignIfUnsetAsmGenerator(ConstructTargetTuple constructTargetTuple, OutputVisitor outputVisitor, org.objectweb.asm.ClassWriter classWriter, BytecodeGenerationContext context)

Method Summary

Modifier and Type	Method	Description
void	generate(ControlFlowChainInstr instr)	Generate bytecode for assign-if-unset.

Methods inherited from class AbstractControlFlowAsmGenerator

branchIfFalse, branchIfTrue, copyResultVariable, createControlFlowLabel, generateCoalescingPattern, jumpTo, placeLabel, processBodyEvaluation, processConditionCase, processConditionCaseWithoutLabelPlacement, processConditionEvaluation, processInstructions, processSequentialCaseChain

Methods inherited from class AbstractAsmGenerator

convertToJvmDescriptor, convertToJvmName, extractFieldName, generateBooleanLiteral, generateCharacterLiteral, generateDebugInfo, generateFloatLiteral, generateIntegerLiteral, generateLoadVariable, generateLocalVariableTable, generateMethodDescriptor, generateObjectLiteral, generateStackOperation, generateStoreVariable, generateStoreVariableAsInt, generateStringLiteral, getCurrentMethodVisitor, getFieldDescriptor, getMethodContext, getOrCreateLabel, getOwnerClassName, getVariableIndex, isFieldAccess, isVariableAllocated, isVariableFieldAccess, setCurrentMethodVisitor, setSharedMethodContext, toJvmFieldName, trackTempVariableFromLiteral, trackTempVariableFromLoad

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

AssignIfUnsetAsmGenerator

AssignIfUnsetAsmGenerator(ConstructTargetTuple constructTargetTuple,
 OutputVisitor outputVisitor,
 org.objectweb.asm.ClassWriter classWriter,
 BytecodeGenerationContext context)

Method Details

generate

public void generate(ControlFlowChainInstr instr)

Generate bytecode for assign-if-unset.

EK9 Pattern: variable :=? value

Semantic Flow:

1. Check if target variable is unset (null or _isSet() returns false)
2. If UNSET: evaluate RHS expression and assign to target
3. If SET: skip assignment (fall through to end)

Stack Frame Invariant: Pre-condition: stack is empty Post-condition: stack is empty (assignment stored in variable)

Parameters:

instr - CONTROL_FLOW_CHAIN instruction with ASSIGN_IF_UNSET type