[SR-6688] Misleading error message when using an object as a bool in an if statement #49237
Labels
bug
A deviation from expected or documented behavior. Also: expected but undesirable behavior.
compiler
The Swift compiler in itself
diagnostics QoI
Bug: Diagnostics Quality of Implementation
type checker
Area → compiler: Semantic analysis
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Environment
Swift 4
Additional Detail from JIRA
md5: 6aface54cec0e448f76d567579e73b05
Issue Description:
This code is invalid in Swift (where `highlightView` is a `UILabel?`):
`if !highlightView {`
However the error the compiler shows is very misleading. The compiler says: "Optional type 'UILabel?' cannot be used as a boolean; test for '!= nil' instead". While this is true for the `highlightView` part, I think it is safe to say that many will instead think this is about the complete condition of the if statement. However the exact opposite should be checked in that case: `== nil`.
Also the fix it that is applied by the compiler changes the above expression to `if  {
which is also suboptimal, unusual and harder to read thanif highlightView )= nil {`.I think this error and its fix it should be optimized in the case of a negated bool check.
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