math: Print special error for logical operators

Until now, something like

`math '7 = 2'`

would complain about a "missing" operator.

Now we print an error about logical operators not being supported and
point the user towards `test`.

Fixes #6096

src/builtin_math.cpp

@@ -149,6 +149,8 @@ static const wchar_t *math_describe_error(te_error_t &error) {
             return _(L"Missing operator");
         case TE_ERROR_UNEXPECTED_TOKEN:
             return _(L"Unexpected token");
+        case TE_ERROR_LOGICAL_OPERATOR:
+            return _(L"Logical operations are not supported, use `test` instead");
         case TE_ERROR_UNKNOWN:
             return _(L"Expression is bogus");
         default:

src/tinyexpr.cpp

@@ -306,6 +306,15 @@ void next_token(state *s) {
                     case '\n':
                     case '\r':
                         break;
+                    case '=':
+                    case '>':
+                    case '<':
+                    case '&':
+                    case '|':
+                    case '!':
+                        s->type = TOK_ERROR;
+                        s->error = TE_ERROR_LOGICAL_OPERATOR;
+                        break;
                     default:
                         s->type = TOK_ERROR;
                         s->error = TE_ERROR_MISSING_OPERATOR;

src/tinyexpr.h

@@ -36,7 +36,8 @@ typedef enum {
     TE_ERROR_TOO_MANY_ARGS = 5,
     TE_ERROR_MISSING_OPERATOR = 6,
     TE_ERROR_UNEXPECTED_TOKEN = 7,
-    TE_ERROR_UNKNOWN = 8
+    TE_ERROR_LOGICAL_OPERATOR = 8,
+    TE_ERROR_UNKNOWN = 9
 } te_error_type_t;
 
 typedef struct te_error_t {

tests/checks/math.fish

@@ -126,3 +126,8 @@ math 0x 3
 # CHECK: 20
 # CHECK: 8
 # CHECK: 0
+
+math "42 >= 1337"
+# CHECKERR: math: Error: Logical operations are not supported, use `test` instead
+# CHECKERR: '42 >= 1337'
+# CHECKERR:     ^