cmd/gc: ensure unique parameter and result names in function types

In addition to fixing the bug, the check is now linear instead of quadratic.

Fixes #4469.

R=ken2
CC=golang-dev
https://golang.org/cl/7773047

2 files changed, 25 insertions, 12 deletions

diff --git a/src/cmd/gc/dcl.c b/src/cmd/gc/dcl.c
index aa2489d9a1..45945467b9 100644
--- a/src/cmd/gc/dcl.c
+++ b/src/cmd/gc/dcl.c
@@ -225,8 +225,12 @@ declare(Node *n, int ctxt)
 	if(ctxt == PAUTO)
 		n->xoffset = 0;
 
-	if(s->block == block)
-		redeclare(s, "in this block");
+	if(s->block == block) {
+		// functype will print errors about duplicate function arguments.
+		// Don't repeat the error here.
+		if(ctxt != PPARAM && ctxt != PPARAMOUT)
+			redeclare(s, "in this block");
+	}
 
 	s->block = block;
 	s->lastlineno = parserline();
@@ -824,22 +828,24 @@ structfield(Node *n)
 	return f;
 }
 
+static uint32 uniqgen;
+
 static void
 checkdupfields(Type *t, char* what)
 {
-	Type* t1;
 	int lno;
 
 	lno = lineno;
 
-	for( ; t; t=t->down)
-		if(t->sym && t->nname && !isblank(t->nname))
-			for(t1=t->down; t1; t1=t1->down)
-				if(t1->sym == t->sym) {
-					lineno = t->nname->lineno;
-					yyerror("duplicate %s %s", what, t->sym->name);
-					break;
-				}
+	for( ; t; t=t->down) {
+		if(t->sym && t->nname && !isblank(t->nname)) {
+			if(t->sym->uniqgen == uniqgen) {
+				lineno = t->nname->lineno;
+				yyerror("duplicate %s %s", what, t->sym->name);
+			} else
+				t->sym->uniqgen = uniqgen;
+		}
+	}
 
 	lineno = lno;
 }
@@ -865,6 +871,7 @@ tostruct(NodeList *l)
 		if(f->broke)
 			t->broke = 1;
 
+	uniqgen++;
 	checkdupfields(t->type, "field");
 
 	if (!t->broke)
@@ -897,7 +904,6 @@ tofunargs(NodeList *l)
 		if(f->broke)
 			t->broke = 1;
 
-	checkdupfields(t->type, "argument");
 	return t;
 }
 
@@ -1004,6 +1010,7 @@ tointerface(NodeList *l)
 		if(f->broke)
 			t->broke = 1;
 
+	uniqgen++;
 	checkdupfields(t->type, "method");
 	t = sortinter(t);
 	checkwidth(t);
@@ -1187,6 +1194,11 @@ functype(Node *this, NodeList *in, NodeList *out)
 	t->type->down = tofunargs(out);
 	t->type->down->down = tofunargs(in);
 
+	uniqgen++;
+	checkdupfields(t->type->type, "argument");
+	checkdupfields(t->type->down->type, "argument");
+	checkdupfields(t->type->down->down->type, "argument");
+
 	if (t->type->broke || t->type->down->broke || t->type->down->down->broke)
 		t->broke = 1;
 
diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h
index 7e5e1b7356..4bfb73e5b7 100644
--- a/src/cmd/gc/go.h
+++ b/src/cmd/gc/go.h
@@ -369,6 +369,7 @@ struct	Sym
 	uchar	sym;		// huffman encoding in object file
 	Sym*	link;
 	int32	npkg;	// number of imported packages with this name
+	uint32	uniqgen;
 
 	// saved and restored by dcopy
 	Pkg*	pkg;