Diagnostics Reference

Every Bee diagnostic code, grouped by module. This is a compiler-builder's single source of truth for the error surface: each code is first registered in registry/diagnostics.json before it may appear in any /spec or /tutorial table. The tables below are generated faithfully to that registry.

Severity legend

Severity	Meaning
E	Hard error — fatal; halts the build or traps at runtime unless handled.
W	Soft warning — non-fatal; logged to stderr and does not change the exit status.

Coding convention

Block rule: module <dd> owns block E<dd>xx, where <dd> is the module's leading digit (01 → E01, 02 → E02, … 14 → E14).
Memory block: module 00 (memory model) has no natural E00xx range (E00xx is reserved for global/deprecation codes), so memory uses the first free block E08xx.
Collision policy: if a proposed code already exists with different semantics, the newer use is bumped to the next free slot in its module block and re-registered. A skipped slot within a block is therefore intentional.

Global codes

Cross-cutting codes shared by every module. Up-scope targets for Phase 7.2 deprecation hardening. Source: spec/00,01,02,03 + decisions D12/D14/D15.

Code	Severity	Condition	Resolution
E0009	E	Upscope target for deprecated symbols/keywords once Phase 7.2 migration completes (replaces E0010/E0011 as hard).	Rewrite using the canonical ratified form.
E0010	E	Legacy form encountered: 'repeat' (use 'next', D15), '≠'/'=='/'!='/'<>' (use '¬'/'='/¬, D12), '.!'/'!.'/'!!' range glyphs (use '..<'/'>..'/'>..<', D13).	Replace with the canonical form; non-fatal until Phase 7.2 hardens to E0009.
E0011	E	Legacy 'using' / 'using:' postfix on io_stmt or rule call (D6).	Use curried named-argument call form (sep: ...); non-fatal until hardened to E0009.
W0901	W	Parser reached a token stream with no statements produced; soft warning attached to parser error surface.	Author statements that the rigid syntax gate recognizes.

E00 / E08 — Memory model

Memory module spec/00-memory-model.md §5. Block moved from the overloaded E04xx range to the free E08xx on 2026-09-14 (spec/04 retains E0401–E0406). Related page: memory.html.

Code	Severity	Condition	Resolution
E0801	E	Read or write of an identifier after a 'zap' statement in the same control-flow graph.	Compile-time fatal error with source line location; runtime 'Panic: UseAfterZap' under -d.
E0802	E	Pointer escapes a Region Arena into an outer scope.	Compiler automatically promotes the allocation from Region to ARC Heap.
E0803	E	Unhandled cycle in an ARC structure.	Static lifetime analysis, or runtime leak warning under -d.
E0804	E	Cross-thread mutation of an unshared reference.	Compile-time data-race restriction.

E01 — Lexical structure

Lexical structure module spec/01-lexical-structure.md §6. Related page: syntax.html.

Code	Severity	Condition	Resolution
E0101	E	Unexpected UTF-8 BOM marker at source start.	Strip the BOM from the source header.
E0102	E	Block comment ('+-') without a closing '-+'.	Ensure closing '-+' exists.
E0103	E	Invalid escape sequence in a string literal.	Use valid \n, \t, \uXXXX escapes.
E0104	E	Single-letter uppercase variable identifier.	Use a lowercase start or a multi-letter type identifier.
E0105	E	Unterminated string literal or markup block.	Check closing quotes or the matching markup tag.

E02 — Statements

Statements module spec/02-statements.md §7 (+ D14/D15). Related page: control.html.

Code	Severity	Condition	Resolution
E0201	E	Statement not aligned to the 2-space offset boundary.	Re-indent to the canonical 2-space block depth.
E0202	E	Mutation of a variable without a prior 'new' declaration.	Declare the variable first.
E0203	E	Missing 'done' or 'return' terminator.	Terminate the block with 'done [label];' (D14) or 'return;'.
E0204	E	Using the '::' clone operator on a non-clonable primitive.	Use ':=' or restrict '::' to boxed/object targets.
E0205	E	Closing label on 'done' does not match the opening header label.	Align 'done' label with the block header label.
E0206	E	'next', 'stop', or 'redo' used outside a loop body.	Move the jump inside a loop (D14/D15).

E03 — Rules

Rules module spec/03-rules.md §7 (+ D6). Related page: rules.html.

Code	Severity	Condition	Resolution
E0301	E	Rule invoked prior to definition or forward declaration.	Define or forward-declare the rule first.
W0301	W	Assertion failed in an 'assert' contract clause.	Logged to stderr; review the asserted invariant.
E0303	E	Expectation failed in an 'expect' contract clause or body statement.	Fatal runtime error if unhandled.
E0304	E	Multi-result rule used inside an arithmetic expression tree.	Call the rule at statement level and deconstruct its results.
E0305	E	Rule block does not end with an aligned 'return;'.	Append 'return;' at the rule end.
E0306	E	Forward declaration does not match the rule implementation signature.	Align the two signatures.
E0307	E	Call site omits a required named-parameter slot binding with no default (D6).	Supply the named argument at the call site.
W0308	W	Curried '(...)' list appended where the rule declares no named slot (D6).	Remove the extraneous named-argument list.
E0309	E	Call site names an identifier not present in the rule's declared named slot (D6).	Use only declared named-slot identifiers.

E04 — Structure

Structure module spec/04-structure.md §7. Retains the canonical E04xx block after memory was bumped to E08xx. Related page: structure.html.

Code	Severity	Condition	Resolution
E0401	E	Secondary or library module contains 'rule main'.	Remove 'rule main' from non-entry modules.
E0402	E	Access to an unexported member (missing '.' prefix).	Export the member with a '.' prefix or access within module.
E0403	E	Module file missing from the search path ($pro_mod, $pro_lib, $bee_lib).	Place the module in a configured search path.
E0404	E	Circular dependency between imported modules.	Break the import cycle.
E0405	E	Attempt to load 'main.bee' via a 'use' directive.	Do not import the entry module.
E0406	E	Scope exited with pending 'begin' threads prior to a 'wait' barrier.	Add a 'wait' barrier before scope exit. (Semantic twin of E1201 in concurrency; retained here for module-level structure completeness.)

E05 — Types

Types module spec/05-types.md §7. Related page: types.html.

Code	Severity	Condition	Resolution
E0501	E	Assigned value violates the static type boundary.	Cast or fix the value to the declared type.
E0502	E	Incompatible explicit cast with the ':>' operator.	Use a lossless cast between compatible types.
E0503	E	Assigned literal falls outside a constrained range/domain.	Constrain the value to the declared domain.
E0504	E	Value exceeds the maximum capacity of a Q(m.n) container.	Widen the fixed-point precision.
E0505	E	User type identifier uses a reserved single uppercase Latin letter.	Choose a non-reserved name or a multi-letter type.
E0506	E	Approximate comparison '≈' executed with uninitialized $max_precision.	Initialize $max_precision before using '≈'.

E06 — Objects

Objects module spec/06-objects.md §7. Related page: objects.html.

Code	Severity	Condition	Resolution
E0601	E	Concrete class fails to supply a body for an inherited abstract method.	Implement the abstract method in the concrete class.
E0602	E	Access to a property without the '.' or 'self.' export prefix.	Export the property or access via 'self.'.
E0603	E	Derived constructor fails to execute a 'super(...)' call.	Chain the parent constructor.
E0604	E	Class hierarchy contains a circular inheritance loop.	Break the inheritance cycle.
E0605	E	Accessing a dynamic key that does not exist in an object dictionary.	Guard the key with a membership check.
E0606	E	Trait applied to an incompatible target type.	Apply the trait only to compatible types.

E07 — Functions

Functions module spec/07-functions.md §7. Related page: functions.html.

Code	Severity	Condition	Resolution
E0701	E	Lambda attempts to invoke a stateful rule.	Use only pure lambdas inside a lambda; hoist the rule call out.
E0702	E	Lambda contains I/O or variable mutation.	Keep lambdas side-effect-free.
E0703	E	Passed lambda signature does not match the expected 'L' parameter.	Align the lambda signature with the 'L' type descriptor.
E0704	E	Lambda references an outer variable not in scope inside the lambda frame.	Pass needed values as lambda parameters.
E0705	E	Use of 'new', 'let', or 'alter' inside a lambda.	Move state declarations outside the lambda.

E10 — Collections

Collections module spec/10-collections.md §5. Related page: collections.html.

Code	Severity	Condition	Resolution
E1001	E	Index less than 1 or greater than the collection length '$'.	Use 1-based indexing; '$-k' for end-relative.
E1002	E	Insertion of a duplicate key/element into Set/Map.	Check membership or allow overwrite.
E1003	E	Incompatible row/column dimension during assignment.	Align matrix dimensions.
E1004	E	Value type does not match the declared collection element type.	Cast the value or change the element type.
E1005	E	Set operator ('∩','∪') applied to a non-set type.	Use set operators only on sets.
E1006	E	Use of index 0 (Bee is 1-based, Decision 1).	Rewrite the index starting from 1.

E11 — Processing

Processing module spec/11-processing.md §7. Related page: processing.html.

Code	Severity	Condition	Resolution
E1101	E	Unboxing a reference into an incompatible scalar type.	Unbox with the correct 'Type(boxed)' target.
E1102	E	Quantifier applied to a non-collection operand.	Apply quantifiers to collections only.
E1103	E	Output type of a pipeline step does not match the next step's input.	Insert an adapting step into the pipeline.
E1104	E	Number of targets exceeds collection elements without a '*' tail.	Add a '*' tail or reduce targets.
E1105	E	Dimension wildcard '*' used on a non-matrix or invalid rank.	Use '*' only on valid matrix ranks.
E1106	E	Reference assignment ':=' on an unboxed value.	Box the value first with '[x]'.

E12 — Concurrency

Concurrency module spec/12-concurrency.md §7. Related page: concurrency.html.

Code	Severity	Condition	Resolution
E1201	E	Scope exited with pending 'begin' threads prior to a 'wait' barrier.	Add a 'wait' barrier before scope exit. (Canonical working code; twin of E0406 in structure.)
E1202	E	Direct cross-thread mutation without a '+>' reduction channel.	Use the '+>' reduction channel.
E1203	E	'yield var << task' on a closed or finished coroutine.	Re-open the channel or check coroutine state.
E1204	E	Unhandled exception in a worker thread surfaced at the 'wait' barrier.	Inspect the '$trial' handle and handle the re-raise.
E1205	E	'yield' used inside a non-coroutine static rule.	Declare the rule as a coroutine or remove 'yield'.

E13 — Graphics

Graphics module spec/13-graphics.md §7. Related page: graphics.html.

Code	Severity	Condition	Resolution
E1301	E	Malformed degree/minute/second ('° ′ ″') angular syntax.	Correct the angular literal.
E1302	E	'draw' on an unattached or non-existent layer.	Attach the layer to the canvas first.
E1303	E	Circle or polar point constructed with a negative radius r.	Use a non-negative radius.
E1304	E	Polygon constructed with fewer than 3 vertex points.	Supply at least 3 vertices.
E1305	E	Target canvas hardware context unavailable.	Retry with a valid canvas context.

E14 — Library

Library module spec/14-library.md §7. Related page: library.html.

Code	Severity	Condition	Resolution
E1401	E	Target file path missing during an open operation.	Create the file or correct the path.
E1402	E	Insufficient OS permissions to open or write a file handle.	Fix the permissions.
E1403	E	Scope exited with an unclosed 'F' file handle.	Close the handle before scope exit.
E1404	E	Requested '$bee.sys' submodule not available in the runtime build.	Build with the required submodule.
E1405	E	File open mode is not 'r', 'w', 'a', or 'rw'.	Use one of the four accepted modes.

Registry contract: when a diagnostic is added, register it first in registry/diagnostics.json in the free slot of its module block. If it collides with an existing code, bump the newer use to the next free slot and re-register — never silently reuse an occupied code with different semantics. Keep this page and every per-module diagnostic table in mirror agreement.