math: Add error length

Like we now do for syntax errors, this marks the extent of the error.

Currently for unknown functions only, would be cool for division too

src/builtins/math.cpp

@@ -258,7 +258,12 @@ static int evaluate_expression(const wchar_t *cmd, const parser_t &parser, io_st
     } else {
         streams.err.append_format(L"%ls: Error: %ls\n", cmd, math_describe_error(error));
         streams.err.append_format(L"'%ls'\n", expression.c_str());
-        streams.err.append_format(L"%*ls%ls\n", error.position - 1, L" ", L"^");
+        if (error.len >= 2) {
+            wcstring tildes(error.len - 2, L'~');
+            streams.err.append_format(L"%*ls%ls%ls%ls\n", error.position - 1, L" ", L"^", tildes.c_str(), L"^");
+        } else {
+            streams.err.append_format(L"%*ls%ls\n", error.position - 1, L" ", L"^");
+        }
         retval = STATUS_CMD_ERROR;
     }
     return retval;

src/tinyexpr.cpp

@@ -113,11 +113,11 @@ struct state {
     double eval() { return expr(); }
 
     [[nodiscard]] te_error_t error() const {
-        if (type_ == TOK_END) return {TE_ERROR_NONE, 0};
+        if (type_ == TOK_END) return {TE_ERROR_NONE, 0, 0};
         // If we have an error position set, use that,
         // otherwise the current position.
         const wchar_t *tok = errpos_ ? errpos_ : next_;
-        te_error_t err{error_, static_cast<int>(tok - start_) + 1};
+        te_error_t err{error_, static_cast<int>(tok - start_) + 1, errlen_};
         if (error_ == TE_ERROR_NONE) {
             // If we're not at the end but there's no error, then that means we have a
             // superfluous token that we have no idea what to do with.
@@ -133,6 +133,7 @@ struct state {
     const wchar_t *start_;
     const wchar_t *next_;
     const wchar_t *errpos_{nullptr};
+    int errlen_{0};
 
     te_fun_t current_{NAN};
     void next_token();
@@ -312,6 +313,9 @@ void state::next_token() {
                     // Our error is more specific, so it takes precedence.
                     type_ = TOK_ERROR;
                     error_ = TE_ERROR_UNKNOWN_FUNCTION;
+                    errpos_ = start + 1;
+                    errlen_ = next_ - start;
+
                 }
             } else {
                 /* Look for an operator or special character. */
@@ -533,6 +537,7 @@ double state::term() {
             error_ = TE_ERROR_DIV_BY_ZERO;
             // Error position is the "/" or "%" sign for now
             errpos_ = tok;
+            errlen_ = 1;
         }
         ret = fn(ret, ret2);
     }

src/tinyexpr.h

@@ -44,6 +44,7 @@ typedef enum {
 typedef struct te_error_t {
     te_error_type_t type;
     int position;
+    int len;
 } te_error_t;
 
 /* Parses the input expression, evaluates it, and frees it. */

tests/checks/math.fish

@@ -113,7 +113,7 @@ not math 'ncr(1)'
 not math 'blah()'
 # CHECKERR: math: Error: Unknown function
 # CHECKERR: 'blah()'
-# CHECKERR:    ^
+# CHECKERR:  ^~~^
 
 math n + 4
 # CHECKERR: math: Error: Unknown function
@@ -167,7 +167,7 @@ math 2x 4
 math 2 x4 # ERROR
 # CHECKERR: math: Error: Unknown function
 # CHECKERR: '2 x4'
-# CHECKERR:     ^
+# CHECKERR:    ^^
 math 0x 3
 # CHECK: 2
 # CHECK: 20