PARSE004

expected an expression

error

verifiedverified on v3.7.0 categoryparser terminalstable code

What it means

Every expression must begin with a prefix-able token (literal, identifier, `(`, `[`, `{`, unary operator, `fn`, ...). Tokens that only occur *between* operands (like `)` or `,`) cannot start an expression.

Trigger condition

An expression is required but the next token cannot start one — for example a closing parenthesis or operator in operand position.

Minimal failing example

let x = ( + 1)

Verified fix

let x = (1 + 1)

When the real problem is an illegal character, the parser groups this diagnostic under the LEX001 root cause.

What the interpreter prints

error[PARSE004]: expected an expression
  --> app.mz:1:16
 1 | let x = ( + 1)
   |                 ^
   |
reason: (the exact problem, with positions)
help:   (a suggested fix appears here)
docs:   https://crossberry-in.github.io/mozhi-doc/errors/PARSE004

Run mozhi --json run app.mz to get the same information as machine-readable JSON (schema mozhi.diagnostics.v1), or --verbose to also show grouped related diagnostics. See the CLI reference.

Suggested fix

Look at what precedes the position: usually an operand is missing between two operators, or a stray closing delimiter appeared early.

Related syntax

Expressions, operators

Related diagnostics

LEX001 PARSE001

Reference links

Limitations

Position points at the token that could not start the expression; the actual omission is usually slightly earlier in the line.