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Fixes dotnet#1631 "zero or more variable_references" → "two or more targets" (grammar requires 2+ elements; targets can be variable_references or discards) Adds: compound_assignment LHS shall not be a discard Adds: simple_assignment and ref_assignment LHS may be a discard Adds: RHS is evaluated even when target is a discard, but no value is stored
BillWagner
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jskeet
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Apr 16, 2026
| > *Note*: ANTLR grammar semantics enforce this requirement due to the ordering of the alternatives. *Semantically* there is no overlap between the four alternatives, this is a syntactic disambiguation. | ||
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| The *simple_assignment* and *compound_assignment* expressions assign a new value to a variable, a property, or an indexer element. Event assignment ([§12.23.6](expressions.md#12236-event-assignment)), a subset of *compound_assignment*, assigns a new value to an event. The *ref_assignment* expression assigns a variable reference ([§9.5](variables.md#95-variable-references)) to a reference variable ([§9.7](variables.md#97-reference-variables-and-returns)). The *deconstructing_assignment* assigns values to zero or more *variable_reference*s. | ||
| The *simple_assignment* and *compound_assignment* expressions assign a new value to a variable, a property, or an indexer element. Event assignment ([§12.23.6](expressions.md#12236-event-assignment)), a subset of *compound_assignment*, assigns a new value to an event. The *ref_assignment* expression assigns a variable reference ([§9.5](variables.md#95-variable-references)) to a reference variable ([§9.7](variables.md#97-reference-variables-and-returns)). The *deconstructing_assignment* assigns values to two or more targets, where each target is either a *variable_reference* or a discard. The left operand of a *simple_assignment* or *ref_assignment* may also be a discard. The left operand of a *compound_assignment* shall not be a discard. When the left operand of a *simple_assignment* or *ref_assignment*, or a target of a *deconstructing_assignment*, is a discard, the corresponding right-side expression is evaluated but no value is stored. |
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Do we want something for the simple assignment at the start of this line too?
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Fixes #1631
"zero or more variable_references" → "two or more targets" (grammar requires 2+ elements; targets can be variable_references or discards)
Adds: compound_assignment LHS shall not be a discard
Adds: simple_assignment and ref_assignment LHS may be a discard
Adds: RHS is evaluated even when target is a discard, but no value is stored