> ## Documentation Index > Fetch the complete documentation index at: https://docs.gorules.io/llms.txt > Use this file to discover all available pages before exploring further. # Static analysis > Reference for every check GoRules runs against your graphs and policies - and how to fix what it finds. GoRules continuously analyses every graph and policy as you edit - no run required. Findings appear in the document's **Problems** tab, on the [Quality Control](/brms/quality/quality-control) page, and as a [pre-flight check](/brms/review/review) when you save. Problems tab showing PREFER_DICTIONARY hints on decision table output columns, with explanations and suggested fixes Each finding has a severity: | Severity | Meaning | | -------- | ----------------------------------------------------------------------------------------------- | | Error | The document will misbehave or fail to evaluate. Fix before shipping. | | Warning | Likely a mistake, but evaluation still works. | | Hint | A quality suggestion. Hints appear in the Problems tab (toggleable) but not on Quality Control. | Static analysis needs to know your types. A graph whose input node has no schema - or an empty one - reports `MISSING_INPUT_SCHEMA` and skips deeper checks until you define one in the [Interface tab](/brms/build/graphs#interface). ## Names and types | Code | What it means | | -------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------ | | `UNDEFINED_VARIABLE` | An expression references a property that nothing declares or computes. Usually a typo or a missing data model property. | | `TYPE_MISMATCH` | A value doesn't match the expected type - often an optional value used in arithmetic without a fallback, or a typed table cell with the wrong kind of value. | | `INVALID_EXPRESSION` | The expression doesn't evaluate against the resolved types. | | `PARSE_ERROR` | The expression isn't valid ZEN syntax. | | `IMPLICIT_ANY` | A schema leaf has no type, so it resolves to `any` and can't be checked. Give it a concrete type. | | `INVALID_NAME` | An identifier contains dots, brackets, or whitespace, or starts with a digit. | | `UNRESOLVED_FUNCTION_TYPE` | A function's return type can't be determined. | | `MAX_DEPTH_EXCEEDED` | Nesting exceeds the analyser's depth limit. | ## Writes and dependencies | Code | What it means | | ------------------------- | ----------------------------------------------------------------------------------------------------------------------- | | `DUPLICATE_WRITER` | Two blocks write the same property. Checked across a policy's whole import group - the conflict can be in another file. | | `CYCLIC_DEPENDENCY` | Rules depend on each other in a loop, so no valid order exists. | | `SELF_REFERENCING_WRITE` | A block writes a property it also reads. | | `INPUT_OVERRIDE` | A rule overwrites a property declared as input. | | `INVALID_WRITE_PATH` | The write target isn't a valid property path. | | `PARTIAL_OBJECT_WRITE` | A block writes part of an object another block writes whole. | | `MIXED_SCOPE` | One block writes multiple entities, or mixes entity and global writes. Split it. | | `UNREACHABLE_ENTITY_READ` | A block reads an entity no execution path can populate. | ## Data models, dictionaries, and imports | Code | What it means | | --------------------------- | ----------------------------------------------------------------------------------------------------------- | | `DATA_MODEL_COLLISION` | The same entity is declared twice with different shapes, or an entity, global, and dictionary share a name. | | `UNKNOWN_DATA_MODEL_TARGET` | A reference points at a name that is neither an entity nor a dictionary. | | `DUPLICATE_PROPERTY` | A data model declares the same property twice. | | `DUPLICATE_ENUM_VALUE` | A dictionary contains the same value twice. | | `IMPORT_NOT_FOUND` | An imported policy path doesn't resolve to a document. | | `CIRCULAR_IMPORT` | Policies import each other in a cycle. | ## Structure and completeness | Code | What it means | | ------------------------------ | ---------------------------------------------------------------------------------------------------- | | `EMPTY_BLOCK` | A block has no content. An error on assertions; a warning on empty tables, matches, and expressions. | | `MISSING_DEFAULT_BRANCH` | A match has no branch for the remaining cases. | | `UNSUPPORTED_NESTED_ITERATION` | Iteration nested deeper than the engine supports. | | `INVALID_GRAPH_STRUCTURE` | The graph's nodes and edges don't form a valid flow. | | `UNREACHABLE_NODE` | A node no path from the input can reach. | | `MISSING_INPUT_SCHEMA` | The graph's input node has no usable schema; deeper checks are skipped. | | `UNCHECKED_NODE` | A node the analyser couldn't verify. | | `NULLABILITY_DIVERGENCE` | A value's nullability differs between paths that later join. | ## Quality hints Hints don't indicate bugs - they point at rules that could be simpler, safer, or easier to maintain. | Code | Suggestion | | --------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------- | | `REDUNDANT_NULLISH` | A `??` fallback on a value that is never null - dead code; remove the fallback. | | `REPEATED_DERIVATION` | The same sub-expression is computed in several places. Compute it once and reference it. | | `PREFER_MATCH` | A construct that would read better as a match block. | | `PREFER_DICTIONARY` | An inline set of fixed values that should be a named [dictionary](/brms/build/policies#dictionaries) - you get membership checking and labels for free. | | `REDUNDANT_TABLE_ROW` | A decision table row that can never produce a distinct outcome. | | `NON_DISCRIMINATING_COLUMN` | A table column that never affects which row matches. | | `REDUNDANT_PARENTHESES` | Parentheses that don't change evaluation. |