add some words (written by rsc) about the state of typed constants.
DELTA=31 (31 added, 0 deleted, 0 changed)
OCL=26709
CL=26716
diff --git a/doc/go_spec.html b/doc/go_spec.html
index 2937249..1f08a55 100644
--- a/doc/go_spec.html
+++ b/doc/go_spec.html
@@ -2950,6 +2950,37 @@
but not <code>uint64</code> or <code>string</code>.
</p>
+<p>
+If a typed constant expression evaluates to a value that is not
+representable by that type, the compiler reports an error.
+</p>
+
+<pre>
+uint8(-1) // error, out of range
+uint8(100) * 100 // error, out of range
+</pre>
+
+<p>
+The size of the mask used by the unary bitwise complement
+operator in a typed constant expression is equal to the size of the
+expression's type. In an ideal constant expression, the bitwise
+complement operator inverts all the bits, producing a negative value.
+</p>
+
+<pre>
+^1 // ideal constant, equal to -2
+uint8(^1) // error, same as uint8(-2), out of range
+^uint8(1) // typed uint8 constant, same as 0xFF ^ uint8(1) = uint8(0xFE)
+int8(^1) // same as int8(-2)
+^int8(1) // error, same as 0xFF ^ int8(1) = int8(0xFE), out of range
+</pre>
+
+<p>
+TODO: perhaps ^ should be disallowed on non-uints instead of assuming twos complement.
+Also it may be possible to make typed constants more like variables, at the cost of fewer
+overflow etc. errors being caught.
+</p>
+
<hr/>
<h2>Statements</h2>
