From 1a91cd6e098ff166527ef6890edaa22716047854 Mon Sep 17 00:00:00 2001
From: Tobias Schmidt <ts@soundcloud.com>
Date: Mon, 25 Jan 2016 13:22:37 -0500
Subject: [PATCH] Rename matrix to range selector in external error messages

The documentation speaks about range vectors and range vector selectors.
This change does not fix all issues, we might still expose the term
"Matrix" in error messages using %T.
---
 promql/parse.go      | 9 +++++----
 promql/parse_test.go | 4 ++++
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/promql/parse.go b/promql/parse.go
index 7ab41d109..198aa4380 100644
--- a/promql/parse.go
+++ b/promql/parse.go
@@ -609,19 +609,20 @@ func (p *parser) unaryExpr() Expr {
 		case *MatrixSelector:
 			s.Offset = offset
 		default:
-			p.errorf("offset modifier must be preceded by a metric or range selector, but follows a %T instead", e)
+			p.errorf("offset modifier must be preceded by an instant or range selector, but follows a %T instead", e)
 		}
 	}
 
 	return e
 }
 
-// rangeSelector parses a matrix selector based on a given vector selector.
+// rangeSelector parses a matrix (a.k.a. range) selector based on a given
+// vector selector.
 //
 //		<vector_selector> '[' <duration> ']'
 //
 func (p *parser) rangeSelector(vs *VectorSelector) *MatrixSelector {
-	const ctx = "matrix selector"
+	const ctx = "range selector"
 	p.next()
 
 	var erange time.Duration
@@ -948,7 +949,7 @@ func (p *parser) offset() time.Duration {
 	return offset
 }
 
-// vectorSelector parses a new vector selector.
+// vectorSelector parses a new (instant) vector selector.
 //
 //		<metric_identifier> [<label_matchers>]
 //		[<metric_identifier>] <label_matchers>
diff --git a/promql/parse_test.go b/promql/parse_test.go
index 020886b3e..21744f6d2 100644
--- a/promql/parse_test.go
+++ b/promql/parse_test.go
@@ -228,6 +228,10 @@ var testExpr = []struct {
 		input:  `*test`,
 		fail:   true,
 		errMsg: "no valid expression found",
+	}, {
+		input:  "1 offset 1d",
+		fail:   true,
+		errMsg: "offset modifier must be preceded by an instant or range selector",
 	},
 	// Vector binary operations.
 	{