11. Static semantics

Programs must pass these checks before lowering.

11.1 Name resolution

Every identifier reference MUST resolve unambiguously to a declaration visible in lexical or module scope.

11.2 Definite declaration

Locals must be declared before use, and var locals must be initialized.

11.3 Returns

Every reachable return path in a non-unit function MUST return a value of the declared type; the final expression is never returned implicitly.

11.4 Dtype equality

Arithmetic tensor operands MUST have identical dtypes after explicit casts and contextual literal typing. Backend-specific implicit promotion MUST NOT leak into Linnet semantics.

11.5 Broadcasting

Broadcast relationships MUST be statically provable (§4.6).

11.6 Index expressions

In a tensor comprehension:

• every output index must have a known domain;
• every non-output index must be bound by a reduction;
• every reduction index must occur in the reduced expression;
• uses of one index must have compatible domains;
• an index repeated in one tensor selects a diagonal and requires compatible axes.

11.7 Effects

fn, op, and entry bodies have no hidden effects. Structural composition and local SSA-style reassignment are not runtime effects. state reads and assignments (§9.3) are explicit effects; each function's state footprint is known statically.

11.8 Recursion

Direct or indirect recursive calls are errors (§8.5).

11.9 Exhaustive match

match over an optional or enum MUST be exhaustive. Duplicate and unreachable arms SHOULD be diagnosed.

11.10 Compile-time values

Dimensions, generic shape parameters, block-array lengths, and static for iteration counts are compile-time values, which runtime tensor contents MUST NOT influence.