blob: 6994e2336dc53efacfe28f732ec75cd1cc8a0723 [file] [log] [blame]
//go:build go1.18
// +build go1.18
package hcl
// This file contains additional diagnostics-related symbols that use the
// Go 1.18 type parameters syntax and would therefore be incompatible with
// Go 1.17 and earlier.
// DiagnosticExtra attempts to retrieve an "extra value" of type T from the
// given diagnostic, if either the diag.Extra field directly contains a value
// of that type or the value implements DiagnosticExtraUnwrapper and directly
// or indirectly returns a value of that type.
//
// Type T should typically be an interface type, so that code which generates
// diagnostics can potentially return different implementations of the same
// interface dynamically as needed.
//
// If a value of type T is found, returns that value and true to indicate
// success. Otherwise, returns the zero value of T and false to indicate
// failure.
func DiagnosticExtra[T any](diag *Diagnostic) (T, bool) {
extra := diag.Extra
var zero T
for {
if ret, ok := extra.(T); ok {
return ret, true
}
if unwrap, ok := extra.(DiagnosticExtraUnwrapper); ok {
// If our "extra" implements DiagnosticExtraUnwrapper then we'll
// unwrap one level and try this again.
extra = unwrap.UnwrapDiagnosticExtra()
} else {
return zero, false
}
}
}