Evolution of Joss 2026: phases 0 and 1

This document records executable decisions following the critical evaluation .The code and tests are the source of truth.

1. Initial state

Baseline of main in 362c26a , before changing semantics:

• go test ./... : correct.
• go vet ./... : correct.
• go build ./... : correct.
• cataloggen --check and docgen --check: correct.
• The parser gave higher precedence to % than to * / / , and treated && and || as equivalent.
• ?? recovered lookup panics, types and other errors and converted them to null.
• 0.0 and {} were true, although 0 , decimal zero and [] were false.
• int → float and float → decimal were implicitly assignable.

2. Semantic decisions

Precedence

The canonical table lives in pkg/parser/parser.go and is published in Syntax .From lowest to highest: assignment, ternary, coalescence, pipeline, OR, AND, equality, comparison, shifts, range, sum, product, prefixes, call and access.* , / and % share a level;&& outperforms || .

Null coalescing

izquierda ?? derecha evaluates derecha only when izquierda terminates normally with null .It does not catch exceptions, panics or program errors. Explicit recovery belongs to try / catch .

Truthiness

Truthiness is preserved because it is already part of existing ternaries, guards, filters and APIs.The table is closed and is based on categories:

Value	False
Absence	null
Boolean	false
Number	zero in int , float or decimal
String	empty
Collection	empty array or map

All other values ​​are true."0" is true because it is non-empty.

Numeric Security

The only implicit promotion between numeric classes is int → decimal , which is exact .int → float , float → decimal and mixed operations that depend on require explicit casting.The integer division, the result of which is float , rejects operands that cannot be represented exactly.The stable code is JOSS-ARITH-003 .

const continues to mean immutable binding.It does not promise immutability of the object, of a collection or of the reachable graph.

3. Compatibility and migration

Change	Class	Automatic migration	Action
Conventional precedence	semantic breaking	Not in general	Add parentheses to preserve the previous result.
?? only for null	breaking and security fix	No	Use try / catch if the recovery was intentional.
Uniform Truthiness	breaking for 0.0 , {} and "0"	No	Explicitly compare when the domain uses another rule.
Strict numerical conversions	static breaking	Partial	Insert floatval(...) or decimal(...) only with revised intent.

A permanent branch of legacy semantics is not introduced.Projects that depend on the above behavior must make their intent visible through parentheses, comparisons, or conversions.

4. Bugs blocked by regression

• Complete arithmetic, logic, comparison, range, shifts, pipeline, coalescence and ternary pipeline.
• Propagation of division by zero and invalid index via ?? .
• Conceptual equality of zero between int , float and decimal .
• Conceptual void equality between arrays and maps.
• Static rejection and runtime defense of known precision losses.

5. Phase 2 — contracts and syntax migration

Phase 2 establishes compatible pieces for the next major version:

• void is a canonical type. A : void callable may use return; or end naturally, while return value emits JOSS-TYPE-008.
• Closures infer a callable type and retain known parameter and return contracts.
• joss check reports migration warnings for let, implicit declarations, legacy constructors and omitted named-callable returns. joss fix safely migrates unambiguous let, nil and Init constructor occurrences.
• null is canonical; the fixer never rewrites text literals or comments.
• async creates a cancellable child context; Future.Cancel() propagates cooperative cancellation to its forked runtime.

const remains binding immutability, not deep object or collection immutability.

6. Surfaces prepared for later phases

The next phase will consolidate var , explicit type, mixed and const , with finite deprecation oflet and implied statements.Before modifying the parser, there must be an inventory of uses, a specific diagnosis and a codemod that only transforms semantically demonstrable cases.

Also inventoried for later phases: mandatory returns and void , closure inference, unknown reduction, native metadata, namespaces, canonical constructor, structured concurrency and profiles capabilities.None alter PHASE 1.

7. Open risks

• floatval expresses deliberate acceptance of approach;Your callers must decide if the domain allows that loss.
• External sources can deliver already approximated floats before converting them to decimal.The suffix m or decimal text avoids that border.
• The VM and plugins have their own testers. equivalence will not be announced until differential testing covers these rules.
• Aggregations, JSON and DB drivers require extended boundary testing without silently altering external contracts.

Index