Constrain Yul assignment LHS to word#487
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tcYulStmt YAssign only unified the assignment LHS with `word` when the variable's type was still a metavariable, letting any concrete non-word type (bool, data, structs, sums) fall through unconstrained. Assembly writes a raw scalar, so a non-word LHS corrupts the variable's tagged inl/inr runtime layout, and the bad write survives every desugaring pass into Yul codegen. Unify the LHS type with `word` unconditionally, mirroring the read path in tcYulExp (YIdent _). Add a negative case test (asm-assign-non-word) asserting that assigning to a bool LHS in assembly is now rejected. Co-Authored-By: Alex Beregszaszi <alex@rtfs.hu>
axic
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Jun 23, 2026
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| function yul_asm_for_body() -> () { | ||
| let result : uint256 = uint256(0); | ||
| let result : word = 0; |
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These three test cases were added in #363 -- makes me wonder if that "fix" wasn't fully correct, and it was eliminated to begin with as the types didn't even match.
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