Class ArgCopyMutation

A detector that highlights cases where function argument mutations are ineffective due to call-by-value semantics in Tact.

Why is it bad?

In Tact, function arguments are passed by value, meaning that any mutations applied to these arguments will only affect the local copy of the variable within the function. Such mutations are unobservable outside the function, except for potentially increasing gas consumption or causing exceptions.

Example

fun addEntry(m: map) {
  m.set(1, 10); // Bad: Mutating the copy
}

Use instead:

fun addEntry() {
  self.m.set(1, 10); // OK: Changing contract's state
}

Alternatively, you could redesign the method:

fun generateNewValue(): Int {
  // ... produce new value for the map
  return self.nextValue + 1;
}

m.set(self.nextKey, self.generateNewValue()); // OK

Hierarchy (view full)

Constructors

constructor

Properties

ctx severity

Accessors

id kind shareImportedWarnings usesSouffle

Methods

check makeWarning skipUnused

Constructors

constructor

Properties

Readonlyctx

ctx: MistiContext

severity

severity: Severity = Severity.HIGH

Gets the severity of the detector.

Accessors

id

  • get id(): string

  • Gets the short identifier of the detector, used in analyzer warnings.

    Returns string

    The unique identifier of the detector.

kind

shareImportedWarnings

  • get shareImportedWarnings(): WarningsBehavior

  • Defines the behavior of warnings generated by this detector when working with multiple projects within a single Tact configuration.

    Here are the available options:

    1. "union" Leave this value if you don't care about warnings generated in other projects.
    2. "intersect" If the warning is generated for some source location of the imported file, it should be generated by each of the projects. Example: Constants from an imported file should not be reported iff they are unused in all the projects, so you need "intersect".

    Returns WarningsBehavior

usesSouffle

  • get usesSouffle(): boolean

  • Checks whether this detector needs the Soufflé binary to be executed.

    Returns boolean

Methods

check

ProtectedmakeWarning

ProtectedskipUnused

Settings

Member Visibility

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Why is it bad?Example
Constructors
Properties
Accessors
Methods