cmd/compile: use "cannot use %s as %s value in %s: %s" error message

This is close to what the compiler used to say, except now we say
"as T value" rather than "as type T" which is closer to the truth
(we cannot use a value as a type, after all). Also, place the primary
error and the explanation (cause) on a single line.

Make respective (single line) adjustment to the matching "cannot
convert" error.

Adjust various tests.

For #55326.

Change-Id: Ib646cf906b11f4129b7ed0c38cf16471f9266b88
Reviewed-on: https://go-review.googlesource.com/c/go/+/436176
Reviewed-by: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

1 files changed, 5 insertions, 5 deletions

diff --git a/test/alias2.go b/test/alias2.go
index d7101420bd..2846e5dc31 100644
--- a/test/alias2.go
+++ b/test/alias2.go
@@ -46,8 +46,8 @@ var _ A0 = T0{}
 var _ T0 = A0{}
 
 // But aliases and original types cannot be used with new types based on them.
-var _ N0 = T0{} // ERROR "cannot use T0{} \(type T0\) as type N0 in assignment|cannot use T0{} \(value of type T0\) as type N0 in variable declaration"
-var _ N0 = A0{} // ERROR "cannot use T0{} \(type T0\) as type N0 in assignment|cannot use A0{} \(value of type T0\) as type N0 in variable declaration"
+var _ N0 = T0{} // ERROR "cannot use T0{} \(value of type T0\) as N0 value in variable declaration"
+var _ N0 = A0{} // ERROR "cannot use A0{} \(value of type T0\) as N0 value in variable declaration"
 
 var _ A5 = Value{}
 
@@ -82,10 +82,10 @@ func _() {
 	var _ A0 = T0{}
 	var _ T0 = A0{}
 
-	var _ N0 = T0{} // ERROR "cannot use T0{} \(type T0\) as type N0 in assignment|cannot use T0{} \(value of type T0\) as type N0 in variable declaration"
-	var _ N0 = A0{} // ERROR "cannot use T0{} \(type T0\) as type N0 in assignment|cannot use A0{} \(value of type T0\) as type N0 in variable declaration"
+	var _ N0 = T0{} // ERROR "cannot use T0{} \(value of type T0\) as N0 value in variable declaration"
+	var _ N0 = A0{} // ERROR "cannot use A0{} \(value of type T0\) as N0 value in variable declaration"
 
-	var _ A5 = Value{} // ERROR "cannot use reflect\.Value{} \(type reflect.Value\) as type A5 in assignment|cannot use Value{} \(value of type reflect.Value\) as type A5 in variable declaration"
+	var _ A5 = Value{} // ERROR "cannot use Value{} \(value of type reflect\.Value\) as A5 value in variable declaration"
 }
 
 // Invalid type alias declarations.