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go/types: tweaks to ArgumentError to be more idiomatic

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This CL makes a few changes to the new ArgumentError type to be more
idiomatic:
 - Use a pointer receiver for methods.
 - Export fields, similarly to Error. ArgumentError has a clear meaning
   (an error associated with an index), so there is no need to hide its
   representation.
 - Add an Unwrap method to access the underlying error.
 - Say explicitly that the error returned from Instantiate may wrap
   *ArgumentError. There is no need to commit to an API that always
   returns an error with dynamic type *ArgumentError.

Updates #47916

Change-Id: Ib1a43e921f247794e7155280ccbf5a6775ed3978
Reviewed-on: https://go-review.googlesource.com/c/go/+/351335
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Robert Findley 2021-09-21 18:15:25 -04:00
parent 04572fa29b
commit 3664950ef6
3 changed files with 15 additions and 13 deletions
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11
src/go/types/api.go
View File

@ -64,15 +64,12 @@ func (err Error) Error() string {
// An ArgumentError holds an error associated with an argument index.
type ArgumentError struct {
index int
error
Index int
Err error
}
// Index returns the positional index of the argument associated with the
// error.
func (e ArgumentError) Index() int {
return e.index
}
func (e *ArgumentError) Error() string { return e.Err.Error() }
func (e *ArgumentError) Unwrap() error { return e.Err }
// An Importer resolves import paths to Packages.
//

11
src/go/types/api_test.go
View File

@ -6,6 +6,7 @@ package types_test
import (
"bytes"
"errors"
"fmt"
"go/ast"
"go/importer"
@ -2000,9 +2001,13 @@ func TestInstantiateErrors(t *testing.T) {
t.Fatalf("Instantiate(%v, %v) returned nil error, want non-nil", T, test.targs)
}
gotAt := err.(ArgumentError).Index()
if gotAt != test.wantAt {
t.Errorf("Instantate(%v, %v): error at index %d, want index %d", T, test.targs, gotAt, test.wantAt)
var argErr *ArgumentError
if !errors.As(err, &argErr) {
t.Fatalf("Instantiate(%v, %v): error is not an *ArgumentError", T, test.targs)
}
if argErr.Index != test.wantAt {
t.Errorf("Instantate(%v, %v): error at index %d, want index %d", T, test.targs, argErr.Index, test.wantAt)
}
}
}

6
src/go/types/instantiate.go
View File

@ -25,8 +25,8 @@ import (
// unimplemented.
//
// If verify is set and constraint satisfaction fails, the returned error may
// be of dynamic type ArgumentError indicating which type argument did not
// satisfy its corresponding type parameter constraint, and why.
// wrap an *ArgumentError indicating which type argument did not satisfy its
// corresponding type parameter constraint, and why.
//
// TODO(rfindley): change this function to also return an error if lengths of
// tparams and targs do not match.
@ -43,7 +43,7 @@ func Instantiate(env *Environment, typ Type, targs []Type, validate bool) (Type,
tparams = t.TypeParams().list()
}
if i, err := (*Checker)(nil).verify(token.NoPos, tparams, targs); err != nil {
return inst, ArgumentError{i, err}
return inst, &ArgumentError{i, err}
}
}