Class GuardedConditionEvaluator

java.lang.Object

org.ek9lang.compiler.phase7.generator.AbstractGenerator

org.ek9lang.compiler.phase7.generator.GuardedConditionEvaluator

public final class GuardedConditionEvaluator
extends AbstractGenerator

Evaluates conditions with optional guard variables for all control flow constructs.

Handles 4 distinct cases:

1. Guard WITH condition AND needs check (e.g., <-, ?=) - Generates LOGICAL_AND_BLOCK with short-circuit evaluation
2. Guard WITH condition but NO check needed (e.g., :=, =) - Just evaluates the condition
3. Condition only (no guard) - Just evaluates the condition
4. Guard only (implicit isSet check) AND needs check - Generates QUESTION_OPERATOR for NULL + isSet checks

This provides consistent guard semantics across all control flow constructs (IF, WHILE, DO-WHILE, SWITCH, TRY) with 90-95% null safety enforcement.

The guard double-check pattern ensures:

1. IS_NULL check (if null → return false)
2. _isSet() check (if not null → check if set)
3. Variable usage (only if both checks pass)

Field Summary

Fields inherited from class AbstractGenerator

debugInfoCreator, instructionBuilder, stackContext, typeNameOrException

Constructor Summary

Constructors

Constructor	Description
GuardedConditionEvaluator(IRGenerationContext stackContext, GeneratorSet generators)

Method Summary

Modifier and Type	Method	Description
ConditionEvaluation	evaluate(EK9Parser.ExpressionContext conditionExpr, EK9Parser.PreFlowStatementContext preFlowStmt, VariableDetails conditionResult, String scopeId, DebugInfo debugInfo)	Evaluates a condition expression that may have guard variables.
(package private) Integer	getGuardOperatorType(EK9Parser.PreFlowStatementContext preFlowStmt)	Determines the guard operator type from a preFlowStatement.
(package private) boolean	requiresGuardCheck(Integer operatorType)	Checks if the given operator requires guard checks (null check + isSet check).

Methods inherited from class AbstractGenerator

createTempVariable, createTempVariableFromContext, extractReturnType, getRecordedSymbolOrException, processBlockStatements, validateNoPreFlowStatement, validateStatementFormOnly

Methods inherited from class Object

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

Constructor Details

GuardedConditionEvaluator

public GuardedConditionEvaluator(IRGenerationContext stackContext,
 GeneratorSet generators)

Method Details

evaluate

public ConditionEvaluation evaluate(EK9Parser.ExpressionContext conditionExpr,
 EK9Parser.PreFlowStatementContext preFlowStmt,
 VariableDetails conditionResult,
 String scopeId,
 DebugInfo debugInfo)

Evaluates a condition expression that may have guard variables.

This is the main entry point that handles all 4 cases of guard/condition combinations. The returned ConditionEvaluation contains both the IR instructions for evaluating the condition and the name of the primitive boolean variable for backend branching.

Parameters:

conditionExpr - Optional explicit condition expression (may be null for guard-only)

preFlowStmt - Optional guard variable declaration/assignment (may be null for condition-only)

conditionResult - Variable to store the condition result (EK9 Boolean type)

scopeId - Scope ID where condition evaluation happens

debugInfo - Debug information for error reporting

Returns:

ConditionEvaluation containing instructions and primitive condition variable name

Throws:

CompilerException - if neither condition nor guard is provided

getGuardOperatorType

Integer getGuardOperatorType(EK9Parser.PreFlowStatementContext preFlowStmt)

Determines the guard operator type from a preFlowStatement. Returns the operator token type, or null if not a guard pattern. Package-private to allow IfStatementGenerator to use for guard variable collection.

Parameters:

preFlowStmt - The preFlowStatement context

Returns:

The operator token type (LEFT_ARROW, ASSIGN, ASSIGN2, GUARD, ASSIGN_UNSET), or null

requiresGuardCheck

boolean requiresGuardCheck(Integer operatorType)

Checks if the given operator requires guard checks (null check + isSet check). Returns true for operators that need guard checks: <-, ?= Returns false for operators that don't: :=, = Package-private to allow IfStatementGenerator to use for guard variable collection.

Parameters:

operatorType - The operator token type

Returns:

true if guard checks are required, false otherwise