gc: eliminate duplicate ambiguous selector message

Also show actual expression in message when possible.

Fixes #2599.

R=ken2
CC=golang-dev
https://golang.org/cl/5654059

diff --git a/src/cmd/gc/subr.c b/src/cmd/gc/subr.c
index d865961104d672ea31526510758cb52ceaab38f0..55932ff3f00ed2a04ac2ce07c13628ff336fb129 100644 (file)
--- a/src/cmd/gc/subr.c
+++ b/src/cmd/gc/subr.c
@@ -2170,8 +2170,11 @@ adddot(Node *n)
        goto ret;
 
 out:
-       if(c > 1)
-               yyerror("ambiguous selector %T.%S", t, s);
+       if(c > 1) {
+               yyerror("ambiguous selector %N", n);
+               n->left = N;
+               return n;
+       }
 
        // rebuild elided dots
        for(c=d-1; c>=0; c--)

diff --git a/src/cmd/gc/typecheck.c b/src/cmd/gc/typecheck.c
index 2339efe072ff5e1fa9f27c0e00fccbeb2a523188..edd6b729d0ebb2e082fbbcfbd058cb56acd3abaf 100644 (file)
--- a/src/cmd/gc/typecheck.c
+++ b/src/cmd/gc/typecheck.c
@@ -20,7 +20,7 @@ static int    twoarg(Node*);
 static int     lookdot(Node*, Type*, int);
 static int     looktypedot(Node*, Type*, int);
 static void    typecheckaste(int, Node*, int, Type*, NodeList*, char*);
-static Type*   lookdot1(Sym *s, Type *t, Type *f, int);
+static Type*   lookdot1(Node*, Sym *s, Type *t, Type *f, int);
 static int     nokeys(NodeList*);
 static void    typecheckcomplit(Node**);
 static void    typecheckas2(Node*);
@@ -581,6 +581,8 @@ reswitch:
        case OXDOT:
                n = adddot(n);
                n->op = ODOT;
+               if(n->left == N)
+                       goto error;
                // fall through
        case ODOT:
                typecheck(&n->left, Erv|Etype);
@@ -1495,6 +1497,7 @@ implicitstar(Node **nn)
        if(!isfixedarray(t))
                return;
        n = nod(OIND, n, N);
+       n->implicit = 1;
        typecheck(&n, Erv);
        *nn = n;
 }
@@ -1554,7 +1557,7 @@ twoarg(Node *n)
 }
 
 static Type*
-lookdot1(Sym *s, Type *t, Type *f, int dostrcmp)
+lookdot1(Node *errnode, Sym *s, Type *t, Type *f, int dostrcmp)
 {
        Type *r;
 
@@ -1565,7 +1568,12 @@ lookdot1(Sym *s, Type *t, Type *f, int dostrcmp)
                if(f->sym != s)
                        continue;
                if(r != T) {
-                       yyerror("ambiguous selector %T.%S", t, s);
+                       if(errnode)
+                               yyerror("ambiguous selector %N", errnode);
+                       else if(isptr[t->etype])
+                               yyerror("ambiguous selector (%T).%S", t, s);
+                       else
+                               yyerror("ambiguous selector %T.%S", t, s);
                        break;
                }
                r = f;
@@ -1582,7 +1590,7 @@ looktypedot(Node *n, Type *t, int dostrcmp)
        s = n->right->sym;
 
        if(t->etype == TINTER) {
-               f1 = lookdot1(s, t, t->type, dostrcmp);
+               f1 = lookdot1(n, s, t, t->type, dostrcmp);
                if(f1 == T)
                        return 0;
 
@@ -1604,7 +1612,7 @@ looktypedot(Node *n, Type *t, int dostrcmp)
                return 0;
 
        expandmeth(f2->sym, f2);
-       f2 = lookdot1(s, f2, f2->xmethod, dostrcmp);
+       f2 = lookdot1(n, s, f2, f2->xmethod, dostrcmp);
        if(f2 == T)
                return 0;
 
@@ -1643,7 +1651,7 @@ lookdot(Node *n, Type *t, int dostrcmp)
        dowidth(t);
        f1 = T;
        if(t->etype == TSTRUCT || t->etype == TINTER)
-               f1 = lookdot1(s, t, t->type, dostrcmp);
+               f1 = lookdot1(n, s, t, t->type, dostrcmp);
 
        f2 = T;
        if(n->left->type == t || n->left->type->sym == S) {
@@ -1651,7 +1659,7 @@ lookdot(Node *n, Type *t, int dostrcmp)
                if(f2 != T) {
                        // Use f2->method, not f2->xmethod: adddot has
                        // already inserted all the necessary embedded dots.
-                       f2 = lookdot1(s, f2, f2->method, dostrcmp);
+                       f2 = lookdot1(n, s, f2, f2->method, dostrcmp);
                }
        }
 
@@ -1666,6 +1674,7 @@ lookdot(Node *n, Type *t, int dostrcmp)
                if(t->etype == TINTER) {
                        if(isptr[n->left->type->etype]) {
                                n->left = nod(OIND, n->left, N);        // implicitstar
+                               n->left->implicit = 1;
                                typecheck(&n->left, Erv);
                        }
                        n->op = ODOTINTER;
@@ -2194,7 +2203,7 @@ typecheckcomplit(Node **np)
                                if(s->pkg != localpkg && exportname(s->name))
                                        s = lookup(s->name);
 
-                               f = lookdot1(s, t, t->type, 0);
+                               f = lookdot1(nil, s, t, t->type, 0);
                                if(f == nil) {
                                        yyerror("unknown %T field '%S' in struct literal", t, s);
                                        continue;

diff --git a/test/fixedbugs/bug412.go b/test/fixedbugs/bug412.go
new file mode 100644 (file)
index 0000000..e05b555
--- /dev/null
+++ b/test/fixedbugs/bug412.go
@@ -0,0 +1,16 @@
+// errchk $G $D/$F.go
+
+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type t struct {
+       x int  // ERROR "duplicate field x"
+       x int
+}
+
+func f(t *t) int {
+       return t.x  // ERROR "ambiguous selector t.x"
+}