json: fix overly-greedy keyword scanning

Logic error in the scanner caused it to always consume the remainder of
the string.

zcl/json/scanner.go

@@ -165,7 +165,7 @@ Byte:
 	for i = 0; i < len(buf); i++ {
 		b := buf[i]
 		switch {
-		case b >= 'a' || b <= 'z' || b >= 'A' || b <= 'Z' || b == '_':
+		case (b >= 'a' && b <= 'z') || (b >= 'A' && b <= 'Z') || b == '_':
 			p.Pos.Byte++
 			p.Pos.Column++
 		default:

zcl/json/scanner_test.go

@@ -510,6 +510,74 @@ func TestScan(t *testing.T) {
 				},
 			},
 		},
+		{
+			`[true]`,
+			[]token{
+				{
+					Type:  tokenBrackO,
+					Bytes: []byte(`[`),
+					Range: zcl.Range{
+						Start: zcl.Pos{
+							Byte:   0,
+							Line:   1,
+							Column: 1,
+						},
+						End: zcl.Pos{
+							Byte:   1,
+							Line:   1,
+							Column: 2,
+						},
+					},
+				},
+				{
+					Type:  tokenKeyword,
+					Bytes: []byte(`true`),
+					Range: zcl.Range{
+						Start: zcl.Pos{
+							Byte:   1,
+							Line:   1,
+							Column: 2,
+						},
+						End: zcl.Pos{
+							Byte:   5,
+							Line:   1,
+							Column: 6,
+						},
+					},
+				},
+				{
+					Type:  tokenBrackC,
+					Bytes: []byte(`]`),
+					Range: zcl.Range{
+						Start: zcl.Pos{
+							Byte:   5,
+							Line:   1,
+							Column: 6,
+						},
+						End: zcl.Pos{
+							Byte:   6,
+							Line:   1,
+							Column: 7,
+						},
+					},
+				},
+				{
+					Type: tokenEOF,
+					Range: zcl.Range{
+						Start: zcl.Pos{
+							Byte:   6,
+							Line:   1,
+							Column: 7,
+						},
+						End: zcl.Pos{
+							Byte:   6,
+							Line:   1,
+							Column: 7,
+						},
+					},
+				},
+			},
+		},
 		{
 			`""`,
 			[]token{