cmd/compile: ignore struct tags when converting structs

Implementation of spec change https://golang.org/cl/24190/.

For #16085.

Change-Id: Id71ef29af5031b073e8be163f578d1bb768ff97a
Reviewed-on: https://go-review.googlesource.com/30169
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 315 insertions, 0 deletions

diff --git a/test/convert2.go b/test/convert2.go
new file mode 100644
index 0000000000..c500638929
--- /dev/null
+++ b/test/convert2.go
@@ -0,0 +1,315 @@
+// errorcheck
+
+// Copyright 2016 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.
+
+// Test various valid and invalid struct assignments and conversions.
+// Does not compile.
+
+package main
+
+type I interface {
+	m()
+}
+
+// conversions between structs
+
+func _() {
+	type S struct{}
+	type T struct{}
+	var s S
+	var t T
+	var u struct{}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u
+	s = S(s)
+	s = S(t)
+	s = S(u)
+	t = u
+	t = T(u)
+}
+
+func _() {
+	type S struct{ x int }
+	type T struct {
+		x int "foo"
+	}
+	var s S
+	var t T
+	var u struct {
+		x int "bar"
+	}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = S(s)
+	s = S(t)
+	s = S(u)
+	t = u // ERROR "cannot use .* in assignment"
+	t = T(u)
+}
+
+func _() {
+	type E struct{ x int }
+	type S struct{ x E }
+	type T struct {
+		x E "foo"
+	}
+	var s S
+	var t T
+	var u struct {
+		x E "bar"
+	}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = S(s)
+	s = S(t)
+	s = S(u)
+	t = u // ERROR "cannot use .* in assignment"
+	t = T(u)
+}
+
+func _() {
+	type S struct {
+		x struct {
+			x int "foo"
+		}
+	}
+	type T struct {
+		x struct {
+			x int "bar"
+		} "foo"
+	}
+	var s S
+	var t T
+	var u struct {
+		x struct {
+			x int "bar"
+		} "bar"
+	}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = S(s)
+	s = S(t)
+	s = S(u)
+	t = u // ERROR "cannot use .* in assignment"
+	t = T(u)
+}
+
+func _() {
+	type E1 struct {
+		x int "foo"
+	}
+	type E2 struct {
+		x int "bar"
+	}
+	type S struct{ x E1 }
+	type T struct {
+		x E2 "foo"
+	}
+	var s S
+	var t T
+	var u struct {
+		x E2 "bar"
+	}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = S(s)
+	s = S(t) // ERROR "cannot convert"
+	s = S(u) // ERROR "cannot convert"
+	t = u    // ERROR "cannot use .* in assignment"
+	t = T(u)
+}
+
+func _() {
+	type E struct{ x int }
+	type S struct {
+		f func(struct {
+			x int "foo"
+		})
+	}
+	type T struct {
+		f func(struct {
+			x int "bar"
+		})
+	}
+	var s S
+	var t T
+	var u struct{ f func(E) }
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = S(s)
+	s = S(t)
+	s = S(u) // ERROR "cannot convert"
+	t = u    // ERROR "cannot use .* in assignment"
+	t = T(u) // ERROR "cannot convert"
+}
+
+// conversions between pointers to structs
+
+func _() {
+	type S struct{}
+	type T struct{}
+	var s *S
+	var t *T
+	var u *struct{}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = (*S)(s)
+	s = (*S)(t)
+	s = (*S)(u)
+	t = u // ERROR "cannot use .* in assignment"
+	t = (*T)(u)
+}
+
+func _() {
+	type S struct{ x int }
+	type T struct {
+		x int "foo"
+	}
+	var s *S
+	var t *T
+	var u *struct {
+		x int "bar"
+	}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = (*S)(s)
+	s = (*S)(t)
+	s = (*S)(u)
+	t = u // ERROR "cannot use .* in assignment"
+	t = (*T)(u)
+}
+
+func _() {
+	type E struct{ x int }
+	type S struct{ x E }
+	type T struct {
+		x E "foo"
+	}
+	var s *S
+	var t *T
+	var u *struct {
+		x E "bar"
+	}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = (*S)(s)
+	s = (*S)(t)
+	s = (*S)(u)
+	t = u // ERROR "cannot use .* in assignment"
+	t = (*T)(u)
+}
+
+func _() {
+	type S struct {
+		x struct {
+			x int "foo"
+		}
+	}
+	type T struct {
+		x struct {
+			x int "bar"
+		} "foo"
+	}
+	var s *S
+	var t *T
+	var u *struct {
+		x struct {
+			x int "bar"
+		} "bar"
+	}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = (*S)(s)
+	s = (*S)(t)
+	s = (*S)(u)
+	t = u // ERROR "cannot use .* in assignment"
+	t = (*T)(u)
+}
+
+func _() {
+	type E1 struct {
+		x int "foo"
+	}
+	type E2 struct {
+		x int "bar"
+	}
+	type S struct{ x E1 }
+	type T struct {
+		x E2 "foo"
+	}
+	var s *S
+	var t *T
+	var u *struct {
+		x E2 "bar"
+	}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = (*S)(s)
+	s = (*S)(t) // ERROR "cannot convert"
+	s = (*S)(u) // ERROR "cannot convert"
+	t = u       // ERROR "cannot use .* in assignment"
+	t = (*T)(u)
+}
+
+func _() {
+	type E struct{ x int }
+	type S struct {
+		f func(struct {
+			x int "foo"
+		})
+	}
+	type T struct {
+		f func(struct {
+			x int "bar"
+		})
+	}
+	var s *S
+	var t *T
+	var u *struct{ f func(E) }
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = (*S)(s)
+	s = (*S)(t)
+	s = (*S)(u) // ERROR "cannot convert"
+	t = u       // ERROR "cannot use .* in assignment"
+	t = (*T)(u) // ERROR "cannot convert"
+}
+
+func _() {
+	type E struct{ x int }
+	type S struct {
+		f func(*struct {
+			x int "foo"
+		})
+	}
+	type T struct {
+		f func(*struct {
+			x int "bar"
+		})
+	}
+	var s *S
+	var t *T
+	var u *struct{ f func(E) }
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = (*S)(s)
+	s = (*S)(t)
+	s = (*S)(u) // ERROR "cannot convert"
+	t = u       // ERROR "cannot use .* in assignment"
+	t = (*T)(u) // ERROR "cannot convert"
+}