hcl/hclsyntax: Fix backtick and tab duplicate detection

hcl/hclsyntax/parser_test.go

@@ -2071,6 +2071,44 @@ block "valid" {}
 				},
 			},
 		},
+		{
+			"a = `str`",
+			2, // Invalid character and expression
+			&Body{
+				Attributes: Attributes{
+					"a": {
+						Name: "a",
+						Expr: &LiteralValueExpr{
+							SrcRange: hcl.Range{
+								Start: hcl.Pos{Line: 1, Column: 5, Byte: 4},
+								End:   hcl.Pos{Line: 1, Column: 6, Byte: 5},
+							},
+						},
+						NameRange: hcl.Range{
+							Start: hcl.Pos{Line: 1, Column: 1, Byte: 0},
+							End:   hcl.Pos{Line: 1, Column: 2, Byte: 1},
+						},
+						EqualsRange: hcl.Range{
+							Start: hcl.Pos{Line: 1, Column: 3, Byte: 2},
+							End:   hcl.Pos{Line: 1, Column: 4, Byte: 3},
+						},
+						SrcRange: hcl.Range{
+							Start: hcl.Pos{Line: 1, Column: 1, Byte: 0},
+							End:   hcl.Pos{Line: 1, Column: 4, Byte: 3},
+						},
+					},
+				},
+				Blocks: Blocks{},
+				SrcRange: hcl.Range{
+					Start: hcl.Pos{Line: 1, Column: 1, Byte: 0},
+					End:   hcl.Pos{Line: 1, Column: 10, Byte: 9},
+				},
+				EndRange: hcl.Range{
+					Start: hcl.Pos{Line: 1, Column: 10, Byte: 9},
+					End:   hcl.Pos{Line: 1, Column: 10, Byte: 9},
+				},
+			},
+		},
 		{
 			"a = sort(data.first.ref.attr)[count.index]\n",
 			0,

hcl/hclsyntax/token.go

@@ -227,14 +227,15 @@ func checkInvalidTokens(tokens Tokens) hcl.Diagnostics {
 		case TokenBacktick:
 			// Only report for alternating (even) backticks, so we won't report both start and ends of the same
 			// backtick-quoted string.
-			if toldExponent < 4 && (toldExponent%2) == 0 {
+			if (toldBacktick % 2) == 0 {
 				diags = append(diags, &hcl.Diagnostic{
 					Severity: hcl.DiagError,
 					Summary:  "Invalid character",
 					Detail:   "The \"`\" character is not valid. To create a multi-line string, use the \"heredoc\" syntax, like \"<<EOT\".",
 					Subject:  &tok.Range,
 				})
-
+			}
+			if toldBacktick <= 2 {
 				toldBacktick++
 			}
 		case TokenSemicolon:
@@ -277,8 +278,6 @@ func checkInvalidTokens(tokens Tokens) hcl.Diagnostics {
 				Detail:   "This character is not used within the language.",
 				Subject:  &tok.Range,
 			})
-
-			toldTabs++
 		}
 	}
 	return diags