Implementation issue for Int-to-Double-conversion

[JekCharlsonYu]

This issue is for tracking implementation of Int-to-Double-conversion:

• Request issue: Annoying to have to write double literals for integer values. #3
• Feature issue: Allow integer literals where a double value is expected. #4
• Feature specification:
  https://github.com/dart-lang/language/blob/master/accepted/2.1/int-literal-as-double-value/feature-specification.md
• Implementation plan: N/A

What: Issue for implementation for Int to Double Conversion

ETA: 10/15 in Dart Repo.

[lrhn]

Issues filed as dart-lang/sdk#34355

[mit-mit]

@JekCharlsonYu what remains on this feature?

[anisalibegic]

@mit-mit I have one thing that bothers me while developing Flutter applications. Are there any reasons why

Error: A value of type 'int' can't be assigned to a variable of type 'double'.

when assigning variable value instead of literal value?

Not working:

int integerValue = 3;
double doubleValue = integerValue;

Working:

double doubleValue = 3;

[lrhn]

Yes, there is a reason.

Dart does not have implicit conversions between class instances. A value which is an int is not also a double, and there is no implicit way to convert it to a double, and so double doubleValue = integerValue; is an error. It's even a compile-time error because there is no way to assign something of type int to a double variable.

What Dart does have is the ability to treat integer literals (like 3) as a double literal (like 3.0) when the integer literal occurs in a place where a double is required. It only works for literals. There is no implicit conversion in that case, there was never any int object created. So double doubleValue = 3; is completely equivalent to double doubleValue = 3.0;, we just allow you to omit the .0 when you know that the numeral will be used as a double anyway.

[ParvinderjitSF]

Why dart is lacking basic features like implicit conversions ? My app getting crashed due to this basic feature

[mateusfccp]

@ParvinderjitSF Can you give a concrete example of what is happening? Preferably a MRE.

[talski]

@ParvinderjitSF Can you give a concrete example of what is happening? Preferably a MRE.

double? doubleValue;
dynamic integerValue = 1;

doubleValue = integerValue;

On flutter windows I get type 'int' is not a subtype of type 'double?'.
On flutter web I got no errors.

Flutter @ master
Dart SDK version: 2.14.0-383.0.dev on "windows_x64"

[mateusfccp]

@talski I can reproduce it on Dart SDK version: 2.13.4 (stable) (Wed Jun 23 13:08:41 2021 +0200) on "macos_x64".

It seems that the web and VM behave differently in this case, which is undesirable.

[mit-mit]

This is a several years old historical issue. For new issues, kindly file a new issue