gc: print error detail about failure to open import

R=ken2
CC=golang-dev
https://golang.org/cl/1872041

diff --git a/src/cmd/gc/lex.c b/src/cmd/gc/lex.c
index 68aa915a91910eba1f17a9da841f42eff703e217..1499c0426ea73ff1030c9bcfeacf93b03db9daae 100644 (file)
--- a/src/cmd/gc/lex.c
+++ b/src/cmd/gc/lex.c
@@ -384,7 +384,7 @@ importfile(Val *f, int line)
 
        imp = Bopen(namebuf, OREAD);
        if(imp == nil) {
-               yyerror("can't open import: %Z", f->u.sval);
+               yyerror("can't open import: %Z: %r", f->u.sval);
                errorexit();
        }
        file = strdup(namebuf);