gc: print detail for typechecking loop error

R=ken2
CC=golang-dev
https://golang.org/cl/5654060

diff --git a/src/cmd/gc/typecheck.c b/src/cmd/gc/typecheck.c
index 91f545849ac70f61fe93e9b5973f8474c07ae985..b791c9e267274bc58676762b99459e3840ab3f40 100644 (file)
--- a/src/cmd/gc/typecheck.c
+++ b/src/cmd/gc/typecheck.c
@@ -111,16 +111,15 @@ typekind(Type *t)
  * replaces *np with a new pointer in some cases.
  * returns the final value of *np as a convenience.
  */
+static void typecheck1(Node **, int);
 Node*
 typecheck(Node **np, int top)
 {
-       int et, aop, op, ptr;
-       Node *n, *l, *r;
-       NodeList *args;
-       int lno, ok, ntop;
-       Type *t, *tp, *ft, *missing, *have, *badtype;
-       Val v;
-       char *why;
+       Node *n;
+       int lno;
+       Fmt fmt;
+       NodeList *l;
+       static NodeList *tcstack, *tcfree;
 
        // cannot type check until all the source has been parsed
        if(!typecheckok)
@@ -157,11 +156,52 @@ typecheck(Node **np, int top)
        }
 
        if(n->typecheck == 2) {
-               yyerror("typechecking loop involving %N", n);
+               if(nsavederrors+nerrors == 0) {
+                       fmtstrinit(&fmt);
+                       for(l=tcstack; l; l=l->next)
+                               fmtprint(&fmt, "\n\t%L %N", l->n->lineno, l->n);
+                       yyerror("typechecking loop involving %N%s", n, fmtstrflush(&fmt));
+               }
                lineno = lno;
                return n;
        }
        n->typecheck = 2;
+       
+       if(tcfree != nil) {
+               l = tcfree;
+               tcfree = l->next;
+       } else
+               l = mal(sizeof *l);
+       l->next = tcstack;
+       l->n = n;
+       tcstack = l;
+
+       typecheck1(&n, top);
+       *np = n;
+       n->typecheck = 1;
+
+       if(tcstack != l)
+               fatal("typecheck stack out of sync");
+       tcstack = l->next;
+       l->next = tcfree;
+       tcfree = l;
+
+       lineno = lno;
+       return n;
+}
+
+static void
+typecheck1(Node **np, int top)
+{
+       int et, aop, op, ptr;
+       Node *n, *l, *r;
+       NodeList *args;
+       int ok, ntop;
+       Type *t, *tp, *ft, *missing, *have, *badtype;
+       Val v;
+       char *why;
+       
+       n = *np;
 
        if(n->sym) {
                if(n->op == ONAME && n->etype != 0 && !(top & Ecall)) {
@@ -1484,10 +1524,7 @@ error:
        n->type = T;
 
 out:
-       lineno = lno;
-       n->typecheck = 1;
        *np = n;
-       return n;
 }
 
 static void