text/template: allow comparison functions to work between any integers

Previously, signed and unsigned integers could not be compared, but
this has problems with things like comparing 'x' with a byte in a string.
Since signed and unsigned integers have a well-defined ordering,
even though their types are different, and since we already allow
comparison regardless of the size of the integers, why not allow it
regardless of the sign?

Integers only, a fine place to draw the line.

Fixes issue 7489.

LGTM=adg
R=golang-codereviews, adg
CC=golang-codereviews
https://codereview.appspot.com/149780043

1 files changed, 48 insertions, 18 deletions

diff --git a/src/text/template/exec_test.go b/src/text/template/exec_test.go
index 663aaf3af..3bffcc159 100644
--- a/src/text/template/exec_test.go
+++ b/src/text/template/exec_test.go
@@ -902,8 +902,8 @@ var cmpTests = []cmpTest{
 	{"eq 1 2", "false", true},
 	{"eq `xy` `xy`", "true", true},
 	{"eq `xy` `xyz`", "false", true},
-	{"eq .Xuint .Xuint", "true", true},
-	{"eq .Xuint .Yuint", "false", true},
+	{"eq .Uthree .Uthree", "true", true},
+	{"eq .Uthree .Ufour", "false", true},
 	{"eq 3 4 5 6 3", "true", true},
 	{"eq 3 4 5 6 7", "false", true},
 	{"ne true true", "false", true},
@@ -916,16 +916,16 @@ var cmpTests = []cmpTest{
 	{"ne 1 2", "true", true},
 	{"ne `xy` `xy`", "false", true},
 	{"ne `xy` `xyz`", "true", true},
-	{"ne .Xuint .Xuint", "false", true},
-	{"ne .Xuint .Yuint", "true", true},
+	{"ne .Uthree .Uthree", "false", true},
+	{"ne .Uthree .Ufour", "true", true},
 	{"lt 1.5 1.5", "false", true},
 	{"lt 1.5 2.5", "true", true},
 	{"lt 1 1", "false", true},
 	{"lt 1 2", "true", true},
 	{"lt `xy` `xy`", "false", true},
 	{"lt `xy` `xyz`", "true", true},
-	{"lt .Xuint .Xuint", "false", true},
-	{"lt .Xuint .Yuint", "true", true},
+	{"lt .Uthree .Uthree", "false", true},
+	{"lt .Uthree .Ufour", "true", true},
 	{"le 1.5 1.5", "true", true},
 	{"le 1.5 2.5", "true", true},
 	{"le 2.5 1.5", "false", true},
@@ -935,9 +935,9 @@ var cmpTests = []cmpTest{
 	{"le `xy` `xy`", "true", true},
 	{"le `xy` `xyz`", "true", true},
 	{"le `xyz` `xy`", "false", true},
-	{"le .Xuint .Xuint", "true", true},
-	{"le .Xuint .Yuint", "true", true},
-	{"le .Yuint .Xuint", "false", true},
+	{"le .Uthree .Uthree", "true", true},
+	{"le .Uthree .Ufour", "true", true},
+	{"le .Ufour .Uthree", "false", true},
 	{"gt 1.5 1.5", "false", true},
 	{"gt 1.5 2.5", "false", true},
 	{"gt 1 1", "false", true},
@@ -945,9 +945,9 @@ var cmpTests = []cmpTest{
 	{"gt 1 2", "false", true},
 	{"gt `xy` `xy`", "false", true},
 	{"gt `xy` `xyz`", "false", true},
-	{"gt .Xuint .Xuint", "false", true},
-	{"gt .Xuint .Yuint", "false", true},
-	{"gt .Yuint .Xuint", "true", true},
+	{"gt .Uthree .Uthree", "false", true},
+	{"gt .Uthree .Ufour", "false", true},
+	{"gt .Ufour .Uthree", "true", true},
 	{"ge 1.5 1.5", "true", true},
 	{"ge 1.5 2.5", "false", true},
 	{"ge 2.5 1.5", "true", true},
@@ -957,11 +957,40 @@ var cmpTests = []cmpTest{
 	{"ge `xy` `xy`", "true", true},
 	{"ge `xy` `xyz`", "false", true},
 	{"ge `xyz` `xy`", "true", true},
-	{"ge .Xuint .Xuint", "true", true},
-	{"ge .Xuint .Yuint", "false", true},
-	{"ge .Yuint .Xuint", "true", true},
+	{"ge .Uthree .Uthree", "true", true},
+	{"ge .Uthree .Ufour", "false", true},
+	{"ge .Ufour .Uthree", "true", true},
+	// Mixing signed and unsigned integers.
+	{"eq .Uthree .Three", "true", true},
+	{"eq .Three .Uthree", "true", true},
+	{"le .Uthree .Three", "true", true},
+	{"le .Three .Uthree", "true", true},
+	{"ge .Uthree .Three", "true", true},
+	{"ge .Three .Uthree", "true", true},
+	{"lt .Uthree .Three", "false", true},
+	{"lt .Three .Uthree", "false", true},
+	{"gt .Uthree .Three", "false", true},
+	{"gt .Three .Uthree", "false", true},
+	{"eq .Ufour .Three", "false", true},
+	{"lt .Ufour .Three", "false", true},
+	{"gt .Ufour .Three", "true", true},
+	{"eq .NegOne .Uthree", "false", true},
+	{"eq .Uthree .NegOne", "false", true},
+	{"ne .NegOne .Uthree", "true", true},
+	{"ne .Uthree .NegOne", "true", true},
+	{"lt .NegOne .Uthree", "true", true},
+	{"lt .Uthree .NegOne", "false", true},
+	{"le .NegOne .Uthree", "true", true},
+	{"le .Uthree .NegOne", "false", true},
+	{"gt .NegOne .Uthree", "false", true},
+	{"gt .Uthree .NegOne", "true", true},
+	{"ge .NegOne .Uthree", "false", true},
+	{"ge .Uthree .NegOne", "true", true},
+	{"eq (index `x` 0) 'x'", "true", true}, // The example that triggered this rule.
+	{"eq (index `x` 0) 'y'", "false", true},
 	// Errors
 	{"eq `xy` 1", "", false},    // Different types.
+	{"eq 2 2.0", "", false},     // Different types.
 	{"lt true true", "", false}, // Unordered types.
 	{"lt 1+0i 1+0i", "", false}, // Unordered types.
 }
@@ -969,13 +998,14 @@ var cmpTests = []cmpTest{
 func TestComparison(t *testing.T) {
 	b := new(bytes.Buffer)
 	var cmpStruct = struct {
-		Xuint, Yuint uint
-	}{3, 4}
+		Uthree, Ufour uint
+		NegOne, Three int
+	}{3, 4, -1, 3}
 	for _, test := range cmpTests {
 		text := fmt.Sprintf("{{if %s}}true{{else}}false{{end}}", test.expr)
 		tmpl, err := New("empty").Parse(text)
 		if err != nil {
-			t.Fatal(err)
+			t.Fatalf("%q: %s", test.expr, err)
 		}
 		b.Reset()
 		err = tmpl.Execute(b, &cmpStruct)