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…wing Fixes informalsystems#1820 ## Problem When a nondet binding has the same name as a state variable, assignments to that variable fail with QNT502 "Variable not set": ```quint module foo { var bar: int action init = { nondet bar = Nat.oneOf() // shadows state var 'bar' bar' = bar // QNT502: Variable bar not set } } ``` The error occurred because the name resolver treated assignment LHS (`bar'`) like any other name reference, resolving it to the most recent definition in scope - the nondet binding instead of the state variable. Since the nondet binding isn't a state variable, the runtime couldn't find a var to update. ## Root Cause In Quint, the assignment operator `bar' = expr` has special semantics: - LHS (`bar`) must always refer to a state variable declaration - RHS (`expr`) follows normal scoping rules and can reference shadowing bindings The resolver wasn't distinguishing between these two contexts, applying standard name resolution to both sides. ## Solution Introduce special handling for assignment LHS in the name resolver: 1. In `enterApp()`, detect `assign` applications and record the LHS name's ID 2. In `enterName()`, check if the name is an assignment LHS 3. If so, use `resolveAssignmentTarget()` which searches for a `var` definition with that name, bypassing any shadowing non-var definitions 4. RHS continues to use standard resolution, correctly picking up shadows This ensures `bar' = bar` in the example above resolves: - LHS `bar` → state variable declaration - RHS `bar` → nondet binding (the shadowing definition) ## Changes - **quint/src/names/resolver.ts**: Add `assignLhsIds` tracking and `resolveAssignmentTarget()` method for special LHS handling - **quint/test/names/resolver.test.ts**: Add regression tests verifying: - All assignment LHS resolve to state vars when shadowed - Assignment RHS correctly resolves to shadowing binding ## Testing - Added unit tests that reproduce the exact issue from informalsystems#1820 - Verified both LHS (state var) and RHS (shadow) resolve correctly - Ran existing test suite to ensure no regressions Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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(including screenshots is helpful)
CHANGELOG.mdfor any new functionality