gc: shift type bug

Fixes #1664.

R=ken2
CC=golang-dev
https://golang.org/cl/4798056

diff --git a/src/cmd/gc/const.c b/src/cmd/gc/const.c
index 8fe9072b23e1ecab0a831593440e0025df46fa39..36a64cb97c2706afa02daf05badbe9ec25d14d49 100644 (file)
--- a/src/cmd/gc/const.c
+++ b/src/cmd/gc/const.c
@@ -947,8 +947,24 @@ defaultlit(Node **np, Type *t)
                        dump("defaultlit", n);
                        fatal("defaultlit");
                }
-               defaultlit(&n->left, t);
-               defaultlit(&n->right, t);
+               // n is ideal, so left and right must both be ideal.
+               // n has not been computed as a constant value,
+               // so either left or right must not be constant.
+               // The only 'ideal' non-constant expressions are shifts.  Ugh.
+               // If one of these is a shift and the other is not, use that type.
+               // When compiling x := 1<<i + 3.14, this means we try to push
+               // the float64 down into the 1<<i, producing the correct error
+               // (cannot shift float64).
+               if(t == T && (n->right->op == OLSH || n->right->op == ORSH)) {
+                       defaultlit(&n->left, T);
+                       defaultlit(&n->right, n->left->type);
+               } else if(t == T && (n->left->op == OLSH || n->left->op == ORSH)) {
+                       defaultlit(&n->right, T);
+                       defaultlit(&n->left, n->right->type);
+               } else {
+                       defaultlit(&n->left, t);
+                       defaultlit(&n->right, t);
+               }
                if(n->type == idealbool || n->type == idealstring)
                        n->type = types[n->type->etype];
                else

diff --git a/test/fixedbugs/bug363.go b/test/fixedbugs/bug363.go
new file mode 100644 (file)
index 0000000..7e89749
--- /dev/null
+++ b/test/fixedbugs/bug363.go
@@ -0,0 +1,21 @@
+// errchk $G $D/$F.go
+
+// 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.
+
+// issue 1664
+
+package main
+
+func main() {
+       var i uint = 33
+       var a = (1<<i) + 4.5  // ERROR "shift of type float64"
+       println(a)
+       
+       var b = (1<<i) + 4.0  // ERROR "shift of type float64"
+       println(b)
+
+       var c int64 = (1<<i) + 4.0  // ok - it's all int64
+       println(b)
+}