Class GuardedAssignmentNeverAppliesOrError

java.lang.Object

org.ek9lang.compiler.common.RuleSupport

org.ek9lang.compiler.common.TypedSymbolAccess

org.ek9lang.compiler.phase5.GuardedAssignmentNeverAppliesOrError

All Implemented Interfaces:

Consumer<EK9Parser.AssignmentStatementContext>

final class GuardedAssignmentNeverAppliesOrError
extends TypedSymbolAccess
implements Consumer<EK9Parser.AssignmentStatementContext>

Detects guarded assignments (:=?) that can never apply (E08095).

:=? assigns ONLY when the target is unset. When the target is provably SET at that point, the assignment is dead and the right-hand side is silently discarded - the code compiles clean and does nothing. This is the same ValueTrackingAnalyzer question already asked by RedundantIsSetCheckOrError, because :=? is an isSet check plus a conditional assign.

The motivating case is a record property initialised to a set value and then assigned in a constructor - which, in a pure constructor, is the only assignment form permitted (E08100), so the mistake is easy to make and invisible:

  Connections
    up as Boolean: false     // SET
    Connections() as pure
      -> isUp as Boolean
      up :=? isUp            // E08095 - never applies, isUp is thrown away

Only the provably-SET case is an error. A provably-UNSET target is the correct and expected use of :=? (it is how a pure constructor initialises its fields), and UNKNOWN stays silent so that no false positive can be raised - EK9 has no warnings, so an error must be certain.

Conditions inside loop bodies are suppressed because widening has not yet been applied, mirroring RedundantIsSetCheckOrError.

Field Summary

Fields inherited from class RuleSupport

errorListener, symbolsAndScopes

Constructor Summary

Constructors

Constructor	Description
GuardedAssignmentNeverAppliesOrError(SymbolsAndScopes symbolsAndScopes, ErrorListener errorListener, ValueTrackingAnalyzer valueTracker)

Method Summary

Modifier and Type	Method	Description
void	accept(EK9Parser.AssignmentStatementContext ctx)

Methods inherited from class TypedSymbolAccess

getRecordedAndTypedSymbol, isProcessingScopePure, recordATypedSymbol

Methods inherited from class Object

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

Methods inherited from interface Consumer

andThen

Constructor Details

GuardedAssignmentNeverAppliesOrError

GuardedAssignmentNeverAppliesOrError(SymbolsAndScopes symbolsAndScopes,
 ErrorListener errorListener,
 ValueTrackingAnalyzer valueTracker)

Method Details

accept

public void accept(EK9Parser.AssignmentStatementContext ctx)

Specified by:

accept in interface Consumer<EK9Parser.AssignmentStatementContext>