Reference

Diagnostics

Every code fang emits, by area.

Diagnostic codes are stable. They are allocated, never reused and retired rather than deleted, so a code in an old log means today what it meant then, and searching for one never lands on a different problem.

Eight areas exist: ELAB, IFACE, TOPO, UNIT, TXN, SIM, IMPORT, MCP.

UNIT: units and dimensions

Code	Means
`UNIT-0001`	Operands of unequal dimension combined
`UNIT-0002`	Unit symbol not recognized
`UNIT-0003`	Exponent is not a dimensionless rational
`UNIT-0004`	Unit conversion rounded

UNIT-0001 is raised where the expression is constructed, not where it is evaluated. A dimensionally invalid expression cannot be stored.

ELAB: elaboration and structure

Code	Means
`ELAB-0001`	Canonical semantic path is not well formed
`ELAB-0002`	Two entities share a canonical semantic path
`ELAB-0003`	Identifier is not unique within the revision
`ELAB-0004`	Entity traceable to neither a source location nor an import
`ELAB-0005`	Connection has no kind
`ELAB-0006`	Required reference names no entity
`ELAB-0007`	Requirement state transition outside the permitted table
`ELAB-0008`	Tool handle read during elaboration
`ELAB-0009`	Artifact declares an unimplemented major schema version
`ELAB-0010`	Cycle where one is prohibited
`ELAB-0011`	Contradictory mandatory constraints
`ELAB-0012`	A second constraint registry was created

ELAB-0012 is the governing invariant as an error code. There is no flag that permits it.

ELAB-0008 is the three-phase rule as an error code: a program that could observe a tool’s result would not be reproducible.

IFACE: interfaces

Code	Means
`IFACE-0001`	A required interface signal has no pin
`IFACE-0002`	Two interfaces disagree on membership
`IFACE-0003`	A pin selector cites no evidence the part declares
`IFACE-0004`	An address strap names a pin the part does not have

An optional signal with no pin is not an error. IFACE-0001 is about signals the interface says it requires.

IFACE-0003 refuses a PinMap whose selectors name no Cites declaration on the same part. An address given as a bare number is UNIT-0001, as any bare-number parameter is. A strap that resolves to no address is not a diagnostic at all: the board is legal, and the compatibility check reports the address as undecided.

TXN: transactions and the gate

Code	Means
`TXN-0001`	Transaction proposed against a snapshot that is no longer current
`TXN-0002`	A required check reported a blocking severity
`TXN-0003`	An undecided result covers a must-be-decided requirement
`TXN-0004`	Policy approval requirements unsatisfied
`TXN-0005`	Operation did not normalize into a well-formed entity

These are the gate conditions. A rejection carries its code, its message and the diff it would have applied.

SIM: simulation and verification

Code	Means
`SIM-0001`	A question measures into a parameter its module does not declare
`SIM-0002`	A question states its own result
`SIM-0003`	A question names a surface or part that resolves to no pins
`SIM-0004`	A circuit question names no bench
`SIM-0005`	A load is neither a current nor a resistance
`SIM-0006`	A model port the part’s pin map does not reach
`SIM-0007`	A frequency outside a model’s range
`SIM-0008`	A rule-check exclusion gives no reason
`SIM-0009`	An emulation model names a descriptor fang does not ship
`SIM-0010`	A component an emulation touches has neither a model nor an abstraction
`SIM-0011`	A fault the device’s emulation model does not support
`SIM-0012`	A stimulus names an input its model lacks, or a value of the wrong dimension
`SIM-0013`	A pin the emulation platform does not map
`SIM-0014`	An emulation names no run duration, or one that is not positive
`SIM-0015`	No firmware is bound, or it was built for another target
`SIM-0016`	A bus device’s controller or address cannot be resolved

SIM-0001, SIM-0002, SIM-0003, SIM-0005 and SIM-0008 fail where the question is written or elaborated, and so does SIM-0014 for a run that is not positive. The others are a question fang verify reports as not runnable, naming what is missing, rather than running it with something assumed in its place. SIM-0009 to SIM-0016 are an emulation plan refused before anything runs; Emulation has the detail.

IMPORT: CAD interchange

Code	Means
`IMPORT-0001`	Adapter could not represent a construct

Reported in import-report.json rather than raised, because an import that stopped at the first unrepresentable construct would be less useful than one that says what it could not carry.

MCP: the agent surface

Code	Means
`MCP-0001`	A path outside the bound project root was named
`MCP-0002`	No tool by that name is exposed
`MCP-0003`	An argument did not parse
`MCP-0004`	Commit named a proposal the gate did not accept
`MCP-0005`	The protocol dependency is not installed
`MCP-0006`	The operation kind is not one the commit gate evaluates

A refusal at the protocol boundary is its own area: it describes the boundary, not the transaction the boundary was asked about.

Adding a code

New codes are allocated through _allocate at the bottom of the relevant area block in fang/diagnostics.py. Never renumber and never reuse a retired number.