gc: remove duplicate errors, give better error for I.(T)

R=ken2
CC=golang-dev
https://golang.org/cl/370041

diff --git a/src/cmd/gc/subr.c b/src/cmd/gc/subr.c
index eaf673f7492d149cb9652d7dcec108707b728afe..97bb60d2e1cff76e3995c8aa351c29a54bf33589 100644 (file)
--- a/src/cmd/gc/subr.c
+++ b/src/cmd/gc/subr.c
@@ -79,7 +79,7 @@ errcmp(const void *va, const void *vb)
                return a->lineno - b->lineno;
        if(a->seq != b->seq)
                return a->seq - b->seq;
-       return 0;
+       return strcmp(a->msg, b->msg);
 }
 
 void
@@ -91,7 +91,8 @@ flusherrors(void)
                return;
        qsort(err, nerr, sizeof err[0], errcmp);
        for(i=0; i<nerr; i++)
-               print("%s", err[i].msg);
+               if(i==0 || strcmp(err[i].msg, err[i-1].msg) != 0)
+                       print("%s", err[i].msg);
        nerr = 0;
 }
 
@@ -3082,11 +3083,19 @@ runifacechecks(void)
                        needexplicit = 1;
                }
                if(wrong) {
-                       if(samename)
-                               yyerror("%T is not %T\n\tmissing %S%hhT\n\tdo have %S%hhT",
-                                       t, iface, m->sym, m->type, samename->sym, samename->type);
-                       else
-                               yyerror("%T is not %T\n\tmissing %S%hhT", t, iface, m->sym, m->type);
+                       if(p->explicit) {
+                               if(samename)
+                                       yyerror("%T cannot contain %T\n\tmissing %S%hhT\n\tdo have %S%hhT",
+                                               iface, t, m->sym, m->type, samename->sym, samename->type);
+                               else
+                                       yyerror("%T cannot contain %T\n\tmissing %S%hhT", iface, t, m->sym, m->type);
+                       } else {
+                               if(samename)
+                                       yyerror("%T is not %T\n\tmissing %S%hhT\n\tdo have %S%hhT",
+                                               t, iface, m->sym, m->type, samename->sym, samename->type);
+                               else
+                                       yyerror("%T is not %T\n\tmissing %S%hhT", t, iface, m->sym, m->type);
+                       }
                }
                else if(!p->explicit && needexplicit) {
                        if(m) {