Constraint Solver

check_constraints(module) walks a parsed Module and reports well-formedness violations (residuated context, effect-name convention, bundle-member resolvability) without invoking the full compiler.

Import from the submodule directly:

from quivers.dsl.constraints import check_constraints, Violation

These names are not re-exported from quivers.dsl.

constraints

Static constraint solver for QVR modules.

Walks a parsed Module and reports well-formedness violations that the unified resolver or the compiler would otherwise only surface at the point of use:

• residuated_constraint: ObjectSlash patterns must reference a residuated universe (a previously-declared TypeFreeResiduated) at every binding site. Schema parameters typed as a residuated universe are recognized; bare ObjectSlash outside a residuated context is flagged.
• effect_constraint: ObjectEffectApply references must name an effect with a conventional name (PascalCase or underscore-containing); other identifiers are flagged.
• bundle_unknown_member: bundle-decl members that do not resolve at parse time (rules / schemas / built-in schema names / other bundles). The LSP relies on this so it can surface bundle problems without invoking the compiler.

The solver consumes the parsed AST only; it never invokes the compiler. Returned diagnostics are Violation records that the qvr check CLI lifts into structured Diagnostic instances.

Violation

Bases: Model

One constraint-solver finding.

check_constraints

check_constraints(module: Module) -> list[Violation]

Return every well-formedness violation in module.

Walks the statements in source order, building up the symbol tables (residuated universes, enum sets, free monoids, declared rule / schema / bundle names) incrementally so that out-of-order references are flagged.

Source code in src/quivers/dsl/constraints.py

def check_constraints(module: Module) -> list[Violation]:
    """Return every well-formedness violation in ``module``.

    Walks the statements in source order, building up the symbol
    tables (residuated universes, enum sets, free monoids, declared
    rule / schema / bundle names) incrementally so that out-of-order
    references are flagged.
    """
    out: list[Violation] = []

    residuated_universes: dict[str, TypeFreeResiduated] = {}
    enum_sets: dict[str, TypeEnumSet] = {}
    free_monoids: dict[str, TypeFreeMonoid] = {}
    aliased_names: dict[str, ObjectExpr] = {}
    rule_names: set[str] = set()
    schema_names: set[str] = set()
    bundle_names: set[str] = set()
    category_atoms: set[str] = set()

    builtin_schemas = set(SCHEMA_REGISTRY.keys())

    def is_residuated_object(name: str) -> bool:
        """True iff ``name`` resolves (via aliases) to a residuated universe."""
        seen: set[str] = set()
        cur = name
        while cur not in seen:
            seen.add(cur)
            if cur in residuated_universes:
                return True
            if cur in aliased_names:
                rhs = aliased_names[cur]
                if isinstance(rhs, TypeName):
                    cur = rhs.name
                    continue
            return False
        return False

    def is_known_effect(name: str) -> bool:
        """True iff ``name`` matches the conventional effect-naming pattern."""
        return bool(name) and (name[0].isupper() or "_" in name)

    def walk_pattern(
        texpr: ObjectExpr,
        *,
        in_residuated_context: bool,
        line_hint: int = 0,
        col_hint: int = 0,
    ) -> None:
        if isinstance(texpr, TypeName):
            return
        if isinstance(texpr, ObjectProduct):
            for c in texpr.components:
                walk_pattern(
                    c,
                    in_residuated_context=in_residuated_context,
                    line_hint=line_hint,
                    col_hint=col_hint,
                )
            return
        if isinstance(texpr, ObjectCoproduct):
            for c in texpr.components:
                walk_pattern(
                    c,
                    in_residuated_context=in_residuated_context,
                    line_hint=line_hint,
                    col_hint=col_hint,
                )
            return
        if isinstance(texpr, ObjectSlash):
            if not in_residuated_context:
                line = texpr.line or line_hint
                col = texpr.col or col_hint
                out.append(
                    Violation(
                        code="residuated_constraint",
                        message=(
                            f"ObjectSlash {texpr.direction!r} appears "
                            "outside a residuated context; either "
                            "declare a FreeResiduated universe and "
                            "parameterize the schema by it, or remove "
                            "the slash"
                        ),
                        line=line,
                        col=col,
                    )
                )
            walk_pattern(
                texpr.result,
                in_residuated_context=in_residuated_context,
                line_hint=line_hint,
                col_hint=col_hint,
            )
            walk_pattern(
                texpr.argument,
                in_residuated_context=in_residuated_context,
                line_hint=line_hint,
                col_hint=col_hint,
            )
            return
        if isinstance(texpr, ObjectEffectApply):
            if not is_known_effect(texpr.effect):
                line = texpr.line or line_hint
                col = texpr.col or col_hint
                out.append(
                    Violation(
                        code="effect_constraint",
                        message=(
                            f"effect {texpr.effect!r} has no "
                            "recognized naming pattern; effect names "
                            "must start with an uppercase letter or "
                            "contain an underscore"
                        ),
                        line=line,
                        col=col,
                    )
                )
            for arg in texpr.args:
                walk_pattern(
                    arg,
                    in_residuated_context=in_residuated_context,
                    line_hint=line_hint,
                    col_hint=col_hint,
                )
            return

    for stmt in module.statements:
        if isinstance(stmt, ObjectDecl):
            init = stmt.init
            if isinstance(init, TypeFreeResiduated):
                residuated_universes[stmt.name] = init
            elif isinstance(init, TypeEnumSet):
                enum_sets[stmt.name] = init
            elif isinstance(init, TypeFreeMonoid):
                free_monoids[stmt.name] = init
            elif isinstance(init, TypeFromExpr):
                aliased_names[stmt.name] = init.expr
        elif isinstance(stmt, CategoryDecl):
            for name in stmt.names:
                category_atoms.add(name)
        elif isinstance(stmt, RuleDecl):
            rule_names.add(stmt.name)
            for prem in stmt.premises:
                walk_pattern(
                    prem,
                    in_residuated_context=True,
                    line_hint=stmt.line,
                    col_hint=stmt.col,
                )
            walk_pattern(
                stmt.conclusion,
                in_residuated_context=True,
                line_hint=stmt.line,
                col_hint=stmt.col,
            )
        elif isinstance(stmt, SchemaDecl):
            schema_names.add(stmt.name)
            in_res = any(
                isinstance(p.type_expr, TypeName)
                and is_residuated_object(p.type_expr.name)
                for p in stmt.parameters
            )
            walk_pattern(
                stmt.domain,
                in_residuated_context=in_res,
                line_hint=stmt.line,
                col_hint=stmt.col,
            )
            walk_pattern(
                stmt.codomain,
                in_residuated_context=in_res,
                line_hint=stmt.line,
                col_hint=stmt.col,
            )
        elif isinstance(stmt, BundleDecl):
            bundle_names.add(stmt.name)
            for member in stmt.rules:
                if (
                    member not in rule_names
                    and member not in schema_names
                    and member not in bundle_names
                    and member not in builtin_schemas
                ):
                    out.append(
                        Violation(
                            code="bundle_unknown_member",
                            message=(
                                f"bundle {stmt.name!r} references "
                                f"unknown member {member!r}; not a "
                                "declared rule / schema / bundle, "
                                "nor a built-in schema"
                            ),
                            line=stmt.line,
                            col=stmt.col,
                        )
                    )

    return out