Compiler Error Index

Each diagnostic emitted from the compiler has a unique error number of the form SCMXXX where XXX is the error number. Error numbers are grouped into ‘categories’ based on the phase in the compiler that emitted the diagnostic.

Currently the diagnostic categories are:

  • 1-9 - Legacy syntax errors.
  • 10-19 - Parser and read.
  • 20-29 - Library declaration and use.
  • 30-39 - Binder diagnostics.
  • 40-49 - Macro definition and expansion.

Parser Errors (10-19)

SCM010 - Parse error

Generic syntax parsing error. This is raised when the parser encounters syntax that cannot be parsed correctly and no more specific error is available.

Possible causes:

  • Unexpected tokens or token sequences
  • Malformed expressions
  • Unterminated strings or identifiers
  • Invalid syntax constructs

Example:

;; Invalid syntax with unclosed parentheses
(define-library .

Or with malformed string or identifier literals:

;; Invalid hex character code in string
"\x;"

;; Unclosed identifier literal
'|\x

Library Errors (20-29)

SCM020 - Improper library name

The library name is valid but does not follow best practices or uses a reserved namespace. This is a warning, not an error.

Possible causes:

  • Using reserved namespace prefixes like “scheme” or “srfi”
  • Library naming conventions not followed

Example:

;; Using reserved 'scheme' prefix
(define-library (scheme custom))

;; Using reserved 'srfi' prefix
(define-library (srfi trust me))

SCM021 - Invalid library name

The library name provided is not valid according to the Scheme library naming rules.

Possible causes:

  • Invalid characters in library name components
  • Improperly formatted library name
  • Expected a library name but found something else

Example:

;; String instead of a list
(define-library "hello")

;; Invalid characters in name component
(define-library (scheme |silly'chars|))

;; Invalid name component (not a symbol)
(define-library (some 't))

SCM022 - Malformed library declaration

A library declaration is syntactically invalid or incorrectly structured.

Possible causes:

  • Missing required components in library declaration
  • Incorrect form of library declaration

Example:

;; Missing library name
(define-library)

;; Improper declaration structure
(define-library (my-lib)
  export) ;; Missing parentheses around export

Binder Errors (30-39)

SCM030 - Invalid or incomplete pattern syntax

A pattern does not follow the expected syntax rules.

Possible causes:

  • Invalid pattern structure in a binding position
  • Incomplete pattern specification

Example:

;; Invalid match pattern
(match x
  ((1 . )) ;; Invalid pattern, missing value after dot
  (#t 1))

SCM031 - Missing export

Warning that occurs when a library attempts to export a symbol that isn’t defined within the library.

Possible causes:

  • Typo in export name
  • Referencing a non-existent definition
  • Export declared before the corresponding definition

Example:

(define-library (missing export)
    ;; Attempting to export symbols that don't exist
    (export we |don't| exist))

SCM032 - Ill-formed special form

A special form (like if, let, set!, etc.) is not syntactically correct.

Possible causes:

  • Wrong number of arguments to a special form
  • Invalid syntax for a special form
  • Malformed special form components

Example:

(define n 1)
(lambda ()
    ;; Malformed set! with closing parenthesis on the next line
    (set! n (+ 1 n) 
    n))

SCM033 - Invalid formal parameter pattern

A formal parameter pattern in a lambda expression or procedure definition is invalid.

Possible causes:

  • Invalid structure in formal parameters list
  • Duplicate parameter names
  • Improper use of rest parameters

Example:

;; Invalid lambda parameters (duplicate parameter name)
(lambda (x y x) 
  (+ x y))

;; Invalid placement of dotted parameter
(lambda (. rest)
  rest)

SCM034 - Invalid let binding

A binding in a let expression is not correctly formed.

Possible causes:

  • Binding not in the form of (name value)
  • Invalid binding structure

Example:

;; Missing value in let binding
(let ((x)) 
  x)

;; Malformed binding (not a proper list)
(let ((x 1 2)) 
  x)

SCM035 - Reference to undefined symbol

A symbol is referenced that hasn’t been defined in the current context.

Possible causes:

  • Typo in variable name
  • Using a variable before it’s defined
  • Referencing a variable outside of its scope
  • Missing import for a library symbol

Example:

;; Using a variable that hasn't been defined
(let-syntax
    ((another (syntax-rules ()
        ((_ a ...) '(a ...)))))
    (another 1 2 3))

;; Attempting to use nonexistent symbol
(display unknown-variable)

SCM036 - Invalid import declaration

An import declaration is invalid or references a non-existent library.

Possible causes:

  • Library doesn’t exist
  • Invalid import set syntax
  • Malformed import specifier

Example:

;; Importing a non-existent library
(import (not a real library))

;; Invalid import structure
(import badthing)

;; Referencing non-existent library in import 
(define-library (test)
    (import (only (test greeter) greet)))

SCM037 - Use of uninitialised variable

A variable is used before it has been initialized, particularly in a letrec binding.

Possible causes:

  • Referencing a variable in a letrec binding before all variables are bound
  • Cyclic dependencies between variables in mutually recursive definitions

Example:

(letrec ((first (+ second 1))  ;; Error: second isn't initialized yet
         (second first))       ;; Error: first's initialization uses second
  second)

(letrec* ((first (- second 100))  ;; Error: second isn't initialized yet
          (second first))         ;; This is fine in letrec*
  second)

SCM038 - Invalid datum value

A datum literal value is invalid or malformed.

Possible causes:

  • Invalid format for a numeric literal
  • Malformed vector or list literal
  • Other invalid literal expressions

Example:

;; Invalid character code
#\x12345

;; Invalid numeric literals
#e1.2.3

;; Malformed vector
#(1 2 . 3)

Macro Errors (40-49)

SCM040 - Macro expansion error

An error occurred while expanding a macro.

Possible causes:

  • No pattern in the macro matched the provided syntax
  • Invalid use of a macro
  • Syntax error in macro template or pattern
  • Invalid dotted form in macro pattern
  • Invalid use of ellipses in macro patterns

Example:

(define-syntax test-macro
    (syntax-rules ::: (test)
        ((_) 'nowt)
        ((_ test things :::) (list things :::))))

;; Error: No pattern matches this use of the macro
(test-macro fail this one)

;; Error: Invalid dotted form in macro pattern
(let-syntax
    ((another (syntax-rules ()
        ((. _) (. "test")))))  ;; Invalid dotted form
    (another 1 2 3))