Compiler #29
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Compiler #29
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apoelstra
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src/policy/compiler.rs
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| /// A Compilation key subtype of another if the type if subtype and other | ||
| /// attributes are equal | ||
| fn is_subtype(self, other: Self) -> bool { | ||
| return self.ty.is_subtype(other.ty) |
apoelstra
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src/policy/compiler.rs
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| #[derive(Copy, Clone, Debug)] | ||
| struct CompilerExtData { | ||
| pub struct CompilerExtData { |
apoelstra
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src/policy/compiler.rs
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| dissat_cost: Some(dissat_cost), | ||
| }) | ||
| } | ||
| } | ||
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|
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| /// Miniscript AST fragment with additional data needed by the compiler | ||
| #[derive(Clone, Debug)] | ||
| struct AstElemExt<Pk: MiniscriptKey> { | ||
| pub struct AstElemExt<Pk: MiniscriptKey> { |
apoelstra
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src/policy/compiler.rs
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| pk_cost as f64 | ||
| + self.sat_cost * sat_prob | ||
| + match (dissat_prob, self.dissat_cost) { | ||
| pub fn cost_1d(&self, sat_prob: f64, dissat_prob: Option<f64>) -> f64 { |
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In the compiler we have a function which inserts the "cast closure" of an expression. It accepts the expression as a candidate as well as a large list of cast-wrapped variants of the expression. For each candidate it rejects it if it is consensus-invalid or has malleable satisfactions. In the original compiler (PR #29) it would decide whether an expression was malleable by checking ty.mall.non_malleable on the miniscript. It had the confusing comment "return malleable types directly" which I believe was supposed to mean "return early if the node is malleable". The comment also observes that "If a elem is malleable, all the casts to it are also going to be malleable" but the code doesn't actually use this fact anywhere. It always tries all the casts. But ok, whatever. Later in #97 (add context to Miniscript) we weakened the malleability check in a bizarre way -- now it checks that the node is malleable according to the type system AND that it is non-malleable according to the context system. That is, we whitelist or_i and d: as "acceptable malleability" in a legacy/bare context. This change, which was not commented on in the original PR, seems like it's just totally wrong. I suspect it was supposed to be an or: if the node is malleable according to the type system OR according to the contextual checks, then skip it. But I'm unsure. (The check is also wrong because the contextual check is wrong; see the last commit.) Anyway, after some fairly heavy fuzzing I was unable to find any instance where this check affects compiler output. I suspect that it's merely an optimization. So change it back to the stronger, simpler check and update the comment.
apoelstra
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Jun 20, 2025
In the compiler we have a function which inserts the "cast closure" of an expression. It accepts the expression as a candidate as well as a large list of cast-wrapped variants of the expression. For each candidate it rejects it if it is consensus-invalid or has malleable satisfactions. In the original compiler (PR rust-bitcoin#29) it would decide whether an expression was malleable by checking ty.mall.non_malleable on the miniscript. It had the confusing comment "return malleable types directly" which I believe was supposed to mean "return early if the node is malleable". The comment also observes that "If a elem is malleable, all the casts to it are also going to be malleable" but the code doesn't actually use this fact anywhere. It always tries all the casts. But ok, whatever. Later in rust-bitcoin#97 (add context to Miniscript) we weakened the malleability check in a bizarre way -- now it checks that the node is malleable according to the type system AND that it is non-malleable according to the context system. That is, we whitelist or_i and d: as "acceptable malleability" in a legacy/bare context. This change, which was not commented on in the original PR, seems like it's just totally wrong. I suspect it was supposed to be an or: if the node is malleable according to the type system OR according to the contextual checks, then skip it. But I'm unsure. (The check is also wrong because the contextual check is wrong; see the last commit.) Anyway, after some fairly heavy fuzzing I was unable to find any instance where this check affects compiler output. I suspect that it's merely an optimization. So change it back to the stronger, simpler check and update the comment.
apoelstra
added a commit
to apoelstra/rust-miniscript
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Jun 20, 2025
In the compiler we have a function which inserts the "cast closure" of an expression. It accepts the expression as a candidate as well as a large list of cast-wrapped variants of the expression. For each candidate it rejects it if it is consensus-invalid or has malleable satisfactions. In the original compiler (PR rust-bitcoin#29) it would decide whether an expression was malleable by checking ty.mall.non_malleable on the miniscript. It had the confusing comment "return malleable types directly" which I believe was supposed to mean "return early if the node is malleable". The comment also observes that "If a elem is malleable, all the casts to it are also going to be malleable" but the code doesn't actually use this fact anywhere. It always tries all the casts. But ok, whatever. Later in rust-bitcoin#97 (add context to Miniscript) we weakened the malleability check in a bizarre way -- now it checks that the node is malleable according to the type system AND that it is non-malleable according to the context system. That is, we whitelist or_i and d: as "acceptable malleability" in a legacy/bare context. This change, which was not commented on in the original PR, seems like it's just totally wrong. I suspect it was supposed to be an or: if the node is malleable according to the type system OR according to the contextual checks, then skip it. But I'm unsure. (The check is also wrong because the contextual check is wrong; see the last commit.) Anyway, after some fairly heavy fuzzing I was unable to find any instance where this check affects compiler output. I suspect that it's merely an optimization. So change it back to the stronger, simpler check and update the comment.
apoelstra
added a commit
to apoelstra/rust-miniscript
that referenced
this pull request
Jun 20, 2025
In the compiler we have a function which inserts the "cast closure" of an expression. It accepts the expression as a candidate as well as a large list of cast-wrapped variants of the expression. For each candidate it rejects it if it is consensus-invalid or has malleable satisfactions. In the original compiler (PR rust-bitcoin#29) it would decide whether an expression was malleable by checking ty.mall.non_malleable on the miniscript. It had the confusing comment "return malleable types directly" which I believe was supposed to mean "return early if the node is malleable". The comment also observes that "If a elem is malleable, all the casts to it are also going to be malleable" but the code doesn't actually use this fact anywhere. It always tries all the casts. But ok, whatever. Later in rust-bitcoin#97 (add context to Miniscript) we weakened the malleability check in a bizarre way -- now it checks that the node is malleable according to the type system AND that it is non-malleable according to the context system. That is, we whitelist or_i and d: as "acceptable malleability" in a legacy/bare context. This change, which was not commented on in the original PR, seems like it's just totally wrong. I suspect it was supposed to be an or: if the node is malleable according to the type system OR according to the contextual checks, then skip it. But I'm unsure. (The check is also wrong because the contextual check is wrong; see the last commit.) Anyway, after some fairly heavy fuzzing I was unable to find any instance where this check affects compiler output. I suspect that it's merely an optimization. So change it back to the stronger, simpler check and update the comment.
apoelstra
added a commit
to apoelstra/rust-miniscript
that referenced
this pull request
Jun 21, 2025
In the compiler we have a function which inserts the "cast closure" of an expression. It accepts the expression as a candidate as well as a large list of cast-wrapped variants of the expression. For each candidate it rejects it if it is consensus-invalid or has malleable satisfactions. In the original compiler (PR rust-bitcoin#29) it would decide whether an expression was malleable by checking ty.mall.non_malleable on the miniscript. It had the confusing comment "return malleable types directly" which I believe was supposed to mean "return early if the node is malleable". The comment also observes that "If a elem is malleable, all the casts to it are also going to be malleable" but the code doesn't actually use this fact anywhere. It always tries all the casts. But ok, whatever. Later in rust-bitcoin#97 (add context to Miniscript) we weakened the malleability check in a bizarre way -- now it checks that the node is malleable according to the type system AND that it is non-malleable according to the context system. That is, we whitelist or_i and d: as "acceptable malleability" in a legacy/bare context. This change, which was not commented on in the original PR, seems like it's just totally wrong. I suspect it was supposed to be an or: if the node is malleable according to the type system OR according to the contextual checks, then skip it. But I'm unsure. (The check is also wrong because the contextual check is wrong; see the last commit.) Anyway, after some fairly heavy fuzzing I was unable to find any instance where this check affects compiler output. I suspect that it's merely an optimization. So change it back to the stronger, simpler check and update the comment.
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This will fail because it depends on other type check PR's to get in first.