cmd/gc: implement len(array) / cap(array) rule
The spec is looser than the current implementation.
The spec edit was made in CL 4444050 (May 2011)
but I never implemented it.
Fixes #3244.
R=ken2
CC=golang-dev
https://golang.org/cl/5785049
diff --git a/src/cmd/gc/typecheck.c b/src/cmd/gc/typecheck.c
index 6dc3fd1..e98d538 100644
--- a/src/cmd/gc/typecheck.c
+++ b/src/cmd/gc/typecheck.c
@@ -190,6 +190,46 @@
return n;
}
+/*
+ * does n contain a call or receive operation?
+ */
+static int callrecvlist(NodeList*);
+
+static int
+callrecv(Node *n)
+{
+ if(n == nil)
+ return 0;
+
+ switch(n->op) {
+ case OCALL:
+ case OCALLMETH:
+ case OCALLINTER:
+ case OCALLFUNC:
+ case ORECV:
+ return 1;
+ }
+
+ return callrecv(n->left) ||
+ callrecv(n->right) ||
+ callrecv(n->ntest) ||
+ callrecv(n->nincr) ||
+ callrecvlist(n->ninit) ||
+ callrecvlist(n->nbody) ||
+ callrecvlist(n->nelse) ||
+ callrecvlist(n->list) ||
+ callrecvlist(n->rlist);
+}
+
+static int
+callrecvlist(NodeList *l)
+{
+ for(; l; l=l->next)
+ if(callrecv(l->n))
+ return 1;
+ return 0;
+}
+
static void
typecheck1(Node **np, int top)
{
@@ -995,12 +1035,14 @@
}
break;
case TARRAY:
- if(t->bound >= 0 && l->op == ONAME) {
- r = nod(OXXX, N, N);
- nodconst(r, types[TINT], t->bound);
- r->orig = n;
- n = r;
- }
+ if(t->bound < 0) // slice
+ break;
+ if(callrecv(l)) // has call or receive
+ break;
+ r = nod(OXXX, N, N);
+ nodconst(r, types[TINT], t->bound);
+ r->orig = n;
+ n = r;
break;
}
n->type = types[TINT];
diff --git a/test/const4.go b/test/const4.go
new file mode 100644
index 0000000..677fcef
--- /dev/null
+++ b/test/const4.go
@@ -0,0 +1,77 @@
+// run
+
+// Copyright 2011 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.
+
+// Test len constants and non-constants, http://golang.org/issue/3244.
+
+package main
+
+var b struct {
+ a[10]int
+}
+
+var m map[string][20]int
+
+var s [][30]int
+
+const (
+ n1 = len(b.a)
+ n2 = len(m[""])
+ n3 = len(s[10])
+)
+
+// Non-constants (see also const5.go).
+var (
+ n4 = len(f())
+ n5 = len(<-c)
+ n6 = cap(g())
+ n7 = cap(<-c1)
+)
+
+var calledF = false
+
+func f() *[40]int {
+ calledF = true
+ return nil
+}
+
+var c = func() chan *[50]int {
+ c := make(chan *[50]int, 2)
+ c <- nil
+ c <- new([50]int)
+ return c
+}()
+
+var calledG = false
+
+func g() *[60]int {
+ calledG = true
+ return nil
+}
+
+var c1 = func() chan *[70]int {
+ c := make(chan *[70]int, 2)
+ c <- nil
+ c <- new([70]int)
+ return c
+}()
+
+func main() {
+ if n1 != 10 || n2 != 20 || n3 != 30 || n4 != 40 || n5 != 50 || n6 != 60 || n7 != 70 {
+ println("BUG:", n1, n2, n3, n4, n5, n6, n7)
+ }
+ if !calledF {
+ println("BUG: did not call f")
+ }
+ if <-c == nil {
+ println("BUG: did not receive from c")
+ }
+ if !calledG {
+ println("BUG: did not call g")
+ }
+ if <-c1 == nil {
+ println("BUG: did not receive from c1")
+ }
+}
diff --git a/test/const5.go b/test/const5.go
new file mode 100644
index 0000000..8e0385e
--- /dev/null
+++ b/test/const5.go
@@ -0,0 +1,33 @@
+// errorcheck
+
+// Copyright 2011 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.
+
+// Test that len non-constants are not constants, http://golang.org/issue/3244.
+
+package p
+
+var b struct {
+ a[10]int
+}
+
+var m map[string][20]int
+
+var s [][30]int
+
+func f() *[40]int
+var c chan *[50]int
+
+const (
+ n1 = len(b.a)
+ n2 = len(m[""])
+ n3 = len(s[10])
+
+ n4 = len(f()) // ERROR "must be constant"
+ n5 = len(<-c) // ERROR "must be constant"
+
+ n6 = cap(f()) // ERROR "must be constant"
+ n7 = cap(<-c) // ERROR "must be constant"
+)
+
