Module embedded_assign 

Pass: lift assignment-as-expression out of mid-statement positions.

HLSL accepts lerp(a, tmp = GetBlur1(uv), b) — the inner tmp = … assigns and yields the new value as the call arg. WGSL has no assignment expression and rejects the source at parse time with “expected ) after call arguments; found Eq” (when our HLSL parser is the one rejecting) or with invalid type for binary operator / similar (when naga sees lerp(a, =, b)).

Rewrite shape: for each enclosing statement that contains one or more embedded Expr::Assign sub-expressions, emit

1. an insertion at the statement’s start with the assignment lifted to a standalone <target> = <value>; (preserving the HLSL side effect),
2. a replacement at the assignment’s position with just the target text (so the surrounding call’s arg count is preserved).

Only fires when the parser produces an Expr::Assign outside the top-level Stmt::Assign slot — i.e. nested inside a Stmt::Return value, an Stmt::LocalDecl init, an Stmt::Expr (typically a bare call), or another Expr::Call’s arg list. Direct Stmt::Assigns are already top-level and don’t need lifting.

Limitations:

• Nested (x = y = z) chains in a call arg lift only the outermost level; the inner chain would re-enter [parse_expr] without going through this pass. Rare in the corpus.
• The lifted assignment runs at the start of the enclosing statement, which is the HLSL evaluation order for the single-assignment case (call args evaluate left-to-right; the assigning arg’s side effect happens before the call). For multiple assigns in the same statement we emit them in source order, which still matches left-to-right.

Constants

RETURN_KW 🔒

Functions

assign_op_str 🔒

collect_embedded 🔒

find_return_keyword_before 🔒

Walk back from byte position expr_start over whitespace, then check for the return keyword. Returns the keyword’s start position when found, None otherwise (which keeps the caller from emitting a misplaced prelude).

rewrite_embedded_assigns 🔒

slice 🔒

stmt_span_start 🔒

walk_block 🔒

walk_stmt 🔒