String interpolation should be used only when there is a mix of variables and string in the same expression.

== Why is this an issue?

String interpolation is a powerful feature in Dart that allows you to embed expressions within string literals.

[source,dart]
----
final expression = 'expressions';
print('a string mixing ${"literals"} and ${2 + 1} ${expressions}');
// Prints 'a string mixing literals and 3 expressions'
----

However, using string interpolation where it is not needed can make the code harder to read and maintain. 

[source,dart]
----
final aString = 'a string';
print('$aString'); // Unnecessary string interpolation
----

It is recommended to use string interpolation only when there is a mix of variables and strings in the same expression.

== How to fix it

Remove the string interpolation and use the interpolated string directly.

=== Code examples

==== Noncompliant code example

[source,dart,diff-id=1,diff-type=noncompliant]
----
final aString = 'a string';
print('$aString'); // Non compliant
----

==== Compliant solution

[source,dart,diff-id=1,diff-type=compliant]
----
final aString = 'a string';
print(aString);
----

== Resources

=== Documentation

* Dart Docs - https://dart.dev/tools/linter-rules/unnecessary_string_interpolations[Linter rule - unnecessary_string_interpolations]
* Dart Docs - https://dart.dev/language/built-in-types#strings[Language - Strings]

ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

Unnecessary use of string interpolation.

=== Highlighting

The entire string, including the string delimiters (`'`, `"`, `'''` or `"""`).

endif::env-github,rspecator-view[]