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Co-authored-by: Camelid <camelidcamel@gmail.com>
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jumbatm 2020-11-16 17:48:41 +10:00 committed by Who? Me?!
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6
src/diagnostics/sessiondiagnostic.md
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@ -30,8 +30,8 @@ tcx.sess.emit_err(FieldAlreadyDeclared {
``` ```
We see that using `SessionDiagnostic` is relatively straight forward. The `#[error = "..."]` We see that using `SessionDiagnostic` is relatively straight forward. The `#[error = "..."]`
attribute is used to supply the error code for the diagnostic. We are then annotate fields in the attribute is used to supply the error code for the diagnostic. We then annotate fields in the
struct with various information of how to convert an instance of the struct into a proper struct with various information on how to convert an instance of the struct into a rendered
diagnostic. The attributes above produce code which is roughly equivalent to the following (in diagnostic. The attributes above produce code which is roughly equivalent to the following (in
pseudo-Rust): pseudo-Rust):
@ -49,7 +49,7 @@ impl SessionDiagnostic for FieldAlreadyDeclared {
``` ```
The generated code draws attention to a number of features. First, we see that within the strings The generated code draws attention to a number of features. First, we see that within the strings
passed to each attribute, we see that field names can be referenced without needing to be passed passed to each attribute, field names can be referenced without needing to be passed
explicitly into the format string -- in this example here, `#[message = "field {field_name} is explicitly into the format string -- in this example here, `#[message = "field {field_name} is
already declared"]` produces a call to `format!` with the appropriate arguments to format already declared"]` produces a call to `format!` with the appropriate arguments to format
`self.field_name` into the string. This applies to strings passed to all attributes. `self.field_name` into the string. This applies to strings passed to all attributes.