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go/test/typeswitch2.go
Matthew Dempsky 0b739fd4df cmd/compile: move duplicate type-case checking into typecheck
Part of the general trend of moving yyerror calls out of walk and into
typecheck.

Notably, this requires splitting test/typeswitch2.go into two files,
because now some of the errors are reported during typecheck and
others are still reported during walk; and if there were any errors
during typecheck, then cmd/compile exits without invoking walk.

Passes toolstash-check.

Change-Id: I05ee0c00b99af659ee1eef098d342d0d736cf31e
Reviewed-on: https://go-review.googlesource.com/c/go/+/194659
Reviewed-by: Robert Griesemer <gri@golang.org>
2019-09-11 23:33:11 +00:00

38 lines
655 B
Go

// errorcheck
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Verify that various erroneous type switches are caught by the compiler.
// Does not compile.
package main
import "io"
func whatis(x interface{}) string {
switch x.(type) {
case int:
return "int"
case int: // ERROR "duplicate"
return "int8"
case io.Reader:
return "Reader1"
case io.Reader: // ERROR "duplicate"
return "Reader2"
case interface {
r()
w()
}:
return "rw"
case interface { // ERROR "duplicate"
w()
r()
}:
return "wr"
}
return ""
}