docs: update smart casting documentation (#7884)
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doc/docs.md
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doc/docs.md
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@ -1888,18 +1888,20 @@ if w is Mars {
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}
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}
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```
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```
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`w` has type `Mars` inside the body of the `if` statement. This is
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`w` has type `Mars` inside the body of the `if` statement. This is
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known as *flow-sensitive typing*. You can also specify a variable name:
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known as *flow-sensitive typing*.
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If `w` is a mutable identifier, it would be unsafe if the compiler smart casts it without a warning.
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That's why you have to declare a `mut` before the `is` expression:
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```v ignore
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```v ignore
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if w is Mars as mars {
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if mut w is Mars {
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assert typeof(w).name == 'World'
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assert typeof(w).name == 'Mars'
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if mars.dust_storm() {
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if w.dust_storm() {
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println('bad weather!')
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println('bad weather!')
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}
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}
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}
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}
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```
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```
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`w` keeps its original type. This form is necessary if `w` is a more
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Otherwise `w` would keep its original type.
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complex expression than just a variable name.
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> This works for both, simple variables and complex expressions like `user.name`
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#### Matching sum types
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#### Matching sum types
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