Fix checks for mixed blocks.

checks.go

@@ -58,18 +58,20 @@ func checkCommentForPeriod(c comment) *Issue {
 		return nil
 	}
 
-	// Shift position by the length of comment's special symbols: /* or //
-	isBlock := strings.HasPrefix(c.lines[0], "/*")
-	if (isBlock && pos.line == 1) || !isBlock {
-		pos.column += 2
-	}
+	// Shift position to its real value. `c.text` doesn't contain comment's
+	// special symbols: /* or //, and line indentations inside. It also
+	// contains */ in the end in case of block comment.
+	pos.column += strings.Index(
+		c.lines[pos.line-1],
+		strings.Split(c.text, "\n")[pos.line-1],
+	)
 
 	iss := Issue{
 		Pos: token.Position{
 			Filename: c.start.Filename,
 			Offset:   c.start.Offset,
 			Line:     pos.line + c.start.Line - 1,
-			Column:   pos.column + c.start.Column - 1,
+			Column:   pos.column,
 		},
 		Message: noPeriodMessage,
 	}

testdata/check/main.go

@@ -46,6 +46,19 @@ Multiline comment with a period [PASS].
 
 // Single-line comment with a period [PASS].
 
+// Mixed block of comments,
+/*
+period must be here [PERIOD_TOP]
+*/
+
+/* Mixed block of comments,
+*/
+// period must be here [PERIOD_TOP]
+
+/*
+// Comment inside comment [PERIOD_TOP]
+*/
+
 // Block comment [PERIOD_DECL]
 const (
 	// Inside comment [PERIOD_DECL]
@@ -104,6 +117,7 @@ func CgoExportedFunction(a, b int) int {
 
 // Кириллица [PERIOD_DECL]
 func NonLatin() string {
+	// Тест: Mixed ASCII and non-ASCII chars.
 	return "привет, мир"
 }