parser: fix a few typos and grammar mistakes

pkg/parser/interface.go

@@ -35,10 +35,10 @@ var (
 	ErrMissingQuote = ParseError("missing quote")
 	// ErrUnexpectedCharacter is a parse error returned when an expression contains an unexpected character.
 	ErrUnexpectedCharacter = ParseError("unexpected character")
-	// ErrMissinggBracket is a parse error returned when an expression is missing an opening or closing bracket.
-	ErrMissinggBracket = ParseError("missing opening or closing bracket []")
-	// ErrMissinggBrace is a parse error returned when an expression is missing an opening or closing brace.
-	ErrMissinggBrace = ParseError("missing opening or closing brace {}")
+	// ErrMissingBracket is a parse error returned when an expression is missing an opening or closing bracket.
+	ErrMissingBracket = ParseError("missing opening or closing bracket []")
+	// ErrMissingBrace is a parse error returned when an expression is missing an opening or closing brace.
+	ErrMissingBrace = ParseError("missing opening or closing brace {}")
 	// ErrCommaInBrackets is a parse error returned when an expression has comma within brackets.
 	ErrCommaInBrackets = ParseError("comma within brackets")
 	// ErrSpacesInMetricName is a parse error returned when an expression has space in metric name.

pkg/parser/parser.go

@@ -582,20 +582,20 @@ FOR:
 		// Graphite render spec: https://graphite.readthedocs.io/en/latest/render_api.html#graphing-metrics
 		switch s[i] {
 		case '{':
-			// No way escape { in metric names, thus supporting it
+			// No way escape { in metric names, thus using it
 			// in the range brackets should be an error.
 			if brackets > 0 {
 				return s, "", ErrBraceInBrackets
 			}
 
 			braces++
 		case '}':
-			// No way escape } in metric names, thus supporting it
+			// No way escape } in metric names, thus using it
 			// in the range brackets should be an error.
 			if brackets > 0 {
 				return s, "", ErrBraceInBrackets
 			} else if braces == 0 {
-				return s, "", ErrMissinggBrace
+				return s, "", ErrMissingBrace
 			}
 
 			braces--
@@ -616,7 +616,7 @@ FOR:
 			// No way to escape braces {} and brackets [] in
 			// graphite query, thus missing open [ means it's a query bug.
 			if brackets == 0 {
-				return s, "", ErrMissinggBracket
+				return s, "", ErrMissingBracket
 			}
 
 			brackets--
@@ -662,10 +662,10 @@ FOR:
 	// No way to escape braces {} and brackets [] in graphite query, thus
 	// missing closed }/] means it's a query bug.
 	if braces > 0 {
-		return s, "", ErrMissinggBrace
+		return s, "", ErrMissingBrace
 	}
 	if brackets > 0 {
-		return s, "", ErrMissinggBracket
+		return s, "", ErrMissingBracket
 	}
 
 	if i == len(s) {