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BEP-006: compiler-errors

Summary

Uniform user-facing experience for compiler errors.

  • Enumerate all errors
  • Give them unique 4-digit codes
  • Specify how each is rendered as a diagnostic message
  • Specify how each is turned into guidance

Motivation

We want to give users and coding agents a uniform experience when they encounter compiler errors.

Proposed Design

  • A top-level compiler_error module contains every error category. 
    pub enum CompilerError<Ty> {
  ParseError(ParseError)
  TypeError(TypeError<Ty>)
}
    (TypeError is parameterized because it's defined here, it needs to contain types, types are defined in another crate that depends on errors, and using types directly would lead to a circular crate dependency).
  • compiler_error has submodules errors pertinent to specific phases. For example type errors are defined in compiler_error::type_error::TypeError. 
    pub enum TypeError<T> {
  TypeMismatch { expected: T, found: T, span: Span },
  UnknownType { name: String, span: Span }.
  ...
}
  • compiler_error::error_format contains error_report_and_code(), which does a giant match over every error variant and specifies how that variant becomes an ariadne report builder and an error code. render_error() takes these two pieces of data and combines them into an ariadne Report.

This design is implemented and merged already, see PR 27651.

All the errors

The following is a list of every possible error. It is derived from both the new compiler (which follows the new scheme), and the legacy compiler (which has a more exhaustive set of errors due to its longer time in development).

Phase: compiler phase (Lexing, Parsing, NameResolution, Typing, Codegen) Error: very brief description in the form of an Enum Variant

Code Phase Error Spans Notes
E0001 Typing TypeMismatch (1) error location, (2) type constraint origin Expected X, found Y
E0002 Typing UnknownType type reference span Type name not found in scope
E0003 Typing UnknownVariable variable reference span Variable name not found in scope
E0004 Typing InvalidOperator operator span Binary or unary op invalid for types
E0005 Typing ArgumentCountMismatch (1) call site, (2) function definition Wrong number of args to function
E0006 Typing NotCallable call site span Calling a non-function type
E0007 Typing NoSuchField (1) field access span, (2) type definition Field doesn't exist on type
E0008 Typing NotIndexable index access span Type doesn't support indexing
E0009 Parsing UnexpectedEof EOF location span Unexpected end of file
E0010 Parsing UnexpectedToken token span Expected X, found Y
E0011 NameResolution DuplicateName (1) second definition, (2) first definition Same name defined twice
E0012 Parsing LiteralParserError literal span Invalid literal value
E0013 Validation ArgumentNotFound argument usage span Required argument missing
E0014 Validation AttributeArgumentNotFound attribute span Attribute missing required arg
E0015 Validation GeneratorArgumentNotFound generator block span Generator missing required arg
E0016 Validation AttributeValidationError attribute span Attribute parsing failed
E0017 Validation DuplicateAttribute attribute span Attribute defined multiple times
E0018 Typing IncompatibleNativeType native type annotation span Native type incompatible
E0019 Typing InvalidNativeTypeArgument native type argument span Invalid arg for native type
E0020 Typing InvalidNativeTypePrefix native type prefix span Wrong prefix for native type
E0021 Validation NativeTypesNotSupported native type span Connector doesn't support native types
E0022 Typing ReservedScalarType type name span Using reserved type name
E0023 NameResolution DuplicateEnumDatabaseName enum span Duplicate DB name for enum
E0024 NameResolution DuplicateModelDatabaseName (1) new model span, (2) existing model span Duplicate DB name for model
E0025 NameResolution DuplicateViewDatabaseName (1) new view span, (2) existing view span Duplicate DB name for view
E0026 NameResolution DuplicateTest (1) test span, (2+) other test spans Test name already defined
E0027 NameResolution DuplicateTopLevel (1) new definition, (2+) existing definitions Top-level name collision
E0028 NameResolution DuplicateConfigKey config key span Key already defined in config
E0029 Validation DuplicateArgument argument span Argument specified twice
E0030 Validation UnusedArgument argument span No such argument exists
E0031 Validation DuplicateDefaultArgument argument span Default arg already specified
E0032 NameResolution DuplicateFunction function span Function already defined
E0033 Parsing InvalidFunctionSyntax function span Malformed function definition
E0034 NameResolution DuplicateEnumValue (1) new value span, (2) existing value span Enum value already defined
E0035 NameResolution DuplicateCompositeTypeField (1) new field span, (2) existing field span Field already on composite type
E0036 NameResolution DuplicateField (1) new field span, (2) existing field span Field already on model/class
E0037 Validation ScalarListFieldsNotSupported field span Connector doesn't support scalar lists
E0038 Validation ModelValidationError model span Generic model validation failure
E0039 Validation NameError name span Invalid identifier name
E0040 Validation EnumValidationError enum span Generic enum validation failure
E0041 Validation CompositeTypeFieldValidation field span Composite type field validation
E0042 Validation FieldValidationError field span Generic field validation failure
E0043 Validation SourceValidationError datasource span Datasource validation failure
E0044 Validation DynamicTypeNotAllowed @dynamic attribute span @dynamic not allowed in type_builder
E0045 Validation ValidationError relevant span Generic validation error
E0046 Parsing LegacyParserError token span Legacy parser catch-all
E0047 Typing OptionalArgumentCountMismatch native type span Wrong optional arg count
E0048 Parsing ParserError token span Expected one of: X, Y, Z
E0049 Typing FunctionalEvaluationError expression span Error evaluating expression
E0050 NameResolution NotFoundError reference span Generic not-found with suggestions
E0051 Typing TypeNotUsedInPrompt type reference span Type not in function output
E0052 NameResolution ClientNotFound client reference span Client name not found
E0053 NameResolution TypeNotFound type reference span Type name not found
E0054 Validation AttributeNotKnown attribute span Unknown attribute name
E0055 Validation PropertyNotKnown property span Unknown property in block
E0056 Validation ArgumentNotKnown argument span Unknown argument name
E0057 Typing ValueParserError value span Expected type X, found Y
E0058 Typing TypeMismatchLegacy value span Legacy type mismatch error
E0059 Validation MissingRequiredProperty block span Required property missing
E0060 Validation ConfigPropertyMissingValue property span Property needs a value
E0061 Typing TypeNotAllowedAsMapKey map key span Invalid map key type
E0062 Typing NonExhaustiveMatch match expression span Match does not cover all cases
E0063 Typing UnreachableMatchArm match arm span Match arm masked by previous patterns

Appendix: Runtime Errors (VM)

These errors occur during execution, not compilation. They are out of scope for this BEP.

Code Category Error Notes
R0001 Runtime StackOverflow Call stack exceeded
R0002 Runtime AssertionError User assertion failed
R0003 Runtime NoSuchKeyInMap Map key not found
R0004 Runtime DivisionByZero Division by zero
R0005 Internal InvalidArgumentCount Wrong arg count (VM bug)
R0006 Internal UnexpectedEmptyStack Stack underflow (VM bug)
R0007 Internal NotEnoughItemsOnStack Stack depth error (VM bug)
R0008 Internal InvalidObjectRef Bad object reference (VM bug)
R0009 Internal TypeError VM type error (VM bug)
R0010 Internal CannotApplyBinOp Invalid binary op (VM bug)
R0011 Internal CannotApplyCmpOp Invalid comparison (VM bug)
R0012 Internal CannotApplyUnaryOp Invalid unary op (VM bug)
R0013 Runtime ArrayIndexOutOfBounds Array index too large
R0014 Runtime ArrayIndexIsNegative Negative array index
R0015 Internal NegativeInstructionPtr Bad instruction ptr (VM bug)