From cc6170934be99c055cc2a5674fffe6303207f570 Mon Sep 17 00:00:00 2001
From: Robert Griesemer <gri@golang.org>
Date: Fri, 21 Nov 2014 13:08:59 -0800
Subject: [PATCH] go/exact: handle unknowns consistently

Fixes golang/go#9147.

LGTM=adonovan
R=adonovan
CC=golang-codereviews
https://golang.org/cl/180110043
---
 go/exact/exact.go      | 10 ++++++----
 go/exact/exact_test.go | 27 +++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/go/exact/exact.go b/go/exact/exact.go
index 06d59188..e8fbfe97 100644
--- a/go/exact/exact.go
+++ b/go/exact/exact.go
@@ -560,14 +560,16 @@ func ord(x Value) int {
 	switch x.(type) {
 	default:
 		return 0
-	case int64Val:
+	case boolVal, stringVal:
 		return 1
-	case intVal:
+	case int64Val:
 		return 2
-	case floatVal:
+	case intVal:
 		return 3
-	case complexVal:
+	case floatVal:
 		return 4
+	case complexVal:
+		return 5
 	}
 }
 
diff --git a/go/exact/exact_test.go b/go/exact/exact_test.go
index c5179708..aa38a896 100644
--- a/go/exact/exact_test.go
+++ b/go/exact/exact_test.go
@@ -346,3 +346,30 @@ func TestBytes(t *testing.T) {
 		}
 	}
 }
+
+func TestUnknown(t *testing.T) {
+	u := MakeUnknown()
+	var values = []Value{
+		u,
+		MakeBool(false), // token.ADD ok below, operation is never considered
+		MakeString(""),
+		MakeInt64(1),
+		MakeFromLiteral("-1234567890123456789012345678901234567890", token.INT),
+		MakeFloat64(1.2),
+		MakeImag(MakeFloat64(1.2)),
+	}
+	for _, val := range values {
+		x, y := val, u
+		for i := range [2]int{} {
+			if i == 1 {
+				x, y = y, x
+			}
+			if got := BinaryOp(x, token.ADD, y); got.Kind() != Unknown {
+				t.Errorf("%s + %s: got %s; want %s", x, y, got, u)
+			}
+			if got := Compare(x, token.EQL, y); got {
+				t.Errorf("%s == %s: got true; want false", x, y)
+			}
+		}
+	}
+}