go/types: better error when converting untyped values in assignments
The error returned by convertUntyped is 'cannot convert _ to _', which
can be misleading in contexts where an explicit conversion would be
allowed.
Arguably the error message from convertUntyped should just be 'cannot
use _ as _', as 'convert' has an explicit meaning within the spec.
Making that change caused a large number of test failures, so for now we
just fix this for assignments by interpreting the error.
For #22070
Change-Id: I4eed6f39d1a991e8df7e035ec301d28a05150eb5
Reviewed-on: https://go-review.googlesource.com/c/go/+/242083
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
diff --git a/src/go/types/assignments.go b/src/go/types/assignments.go
index 34a9d784..9697e50 100644
--- a/src/go/types/assignments.go
+++ b/src/go/types/assignments.go
@@ -7,6 +7,7 @@
package types
import (
+ "errors"
"go/ast"
"go/token"
)
@@ -43,8 +44,16 @@
}
target = Default(x.typ)
}
- check.convertUntyped(x, target)
- if x.mode == invalid {
+ if err := check.canConvertUntyped(x, target); err != nil {
+ var internalErr Error
+ var msg string
+ if errors.As(err, &internalErr) {
+ msg = internalErr.Msg
+ } else {
+ msg = err.Error()
+ }
+ check.errorf(x.pos(), "cannot use %s as %s value in %s: %v", x, target, context, msg)
+ x.mode = invalid
return
}
}
