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Rust: Refactor using shared constraint satisfaction #20682

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04b0ed6
Rust: Refactor using shared constraint satisfaction
paldepind Oct 24, 2025
3ceb033
Rust: Fix typo from review
paldepind Oct 24, 2025
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8 changes: 4 additions & 4 deletions rust/ql/lib/codeql/rust/internal/TypeInference.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -822,7 +822,7 @@ private predicate assocFunctionInfo(
) {
f = i.getASuccessor(name) and
arity = f.getParamList().getNumberOfParams() and
t.appliesTo(f, pos, i)
t.appliesTo(f, i, pos)
}

/**
Expand Down Expand Up @@ -1622,7 +1622,7 @@ private module MethodResolution {
predicate toCheck(ImplOrTraitItemNode i, Function f, FunctionPosition pos, AssocFunctionType t) {
exists(TypePath path, Type t0 |
FunctionOverloading::functionResolutionDependsOnArgument(i, f, pos, path, t0) and
t.appliesTo(f, pos, i) and
t.appliesTo(f, i, pos) and
// for now, we do not handle ambiguous targets when one of the types it iself
// a type parameter; we should be checking the constraints on that type parameter
// in this case
Expand Down Expand Up @@ -1855,7 +1855,7 @@ private module NonMethodResolution {
ImplItemNode impl, NonMethodFunction implFunction
) {
exists(TypePath path |
assocFunctionTypeAt(implFunction, impl, pos, path, type) and
type = assocFunctionTypeAt(implFunction, impl, pos, path) and
implFunction.implements(traitFunction) and
FunctionOverloading::traitTypeParameterOccurrence(trait, traitFunction, _, pos, path, _)
|
Expand Down Expand Up @@ -2069,7 +2069,7 @@ private module NonMethodResolution {

private module NonMethodArgsAreInstantiationsOfInput implements ArgsAreInstantiationsOfInputSig {
predicate toCheck(ImplOrTraitItemNode i, Function f, FunctionPosition pos, AssocFunctionType t) {
t.appliesTo(f, pos, i) and
t.appliesTo(f, i, pos) and
(
exists(Type t0 |
// for now, we do not handle ambiguous targets when one of the types it iself
Expand Down
4 changes: 2 additions & 2 deletions rust/ql/lib/codeql/rust/internal/typeinference/FunctionOverloading.qll
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Expand Up @@ -79,7 +79,7 @@ predicate traitTypeParameterOccurrence(
TypeParameter tp
) {
f = trait.getASuccessor(functionName) and
assocFunctionTypeAt(f, trait, pos, path, tp) and
tp = assocFunctionTypeAt(f, trait, pos, path) and
tp = trait.(TraitTypeAbstraction).getATypeParameter()
}

Expand Down Expand Up @@ -120,7 +120,7 @@ predicate functionResolutionDependsOnArgument(
exists(TraitItemNode trait, string functionName |
implHasSibling(impl, trait) and
traitTypeParameterOccurrence(trait, _, functionName, pos, path, _) and
assocFunctionTypeAt(f, impl, pos, path, type) and
type = assocFunctionTypeAt(f, impl, pos, path) and
f = impl.getASuccessor(functionName) and
pos.isPosition()
)
Expand Down
140 changes: 52 additions & 88 deletions rust/ql/lib/codeql/rust/internal/typeinference/FunctionType.qll
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Expand Up @@ -72,28 +72,54 @@ module FunctionPositionMatchingInput {
}

private newtype TAssocFunctionType =
MkAssocFunctionType(Function f, FunctionPosition pos, ImplOrTraitItemNode i) {
f = i.getAnAssocItem() and
exists(pos.getTypeMention(f))
} or
MkInheritedAssocFunctionType(
Function f, FunctionPosition pos, TypeMention parentMention, TraitItemNode parent,
ImplOrTraitItemNode i
) {
exists(AssocFunctionType inherited |
inherited.appliesTo(f, pos, parent) and
f = i.getASuccessor(_)
/** An associated function `f` that should be specialized for `i` at `pos`. */
MkAssocFunctionType(Function f, ImplOrTraitItemNode i, FunctionPosition pos) {
f = i.getASuccessor(_) and exists(pos.getTypeMention(f))
}

bindingset[condition, constraint, tp]
private Type traitConstraintTypeAt(
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getTraitConstraintTypeAt.

TypeMention condition, TypeMention constraint, TypeParameter tp, TypePath path
) {
BaseTypes::conditionSatisfiesConstraintTypeAt(_, condition, constraint,
TypePath::singleton(tp).appendInverse(path), result)
}

/**
* Gets if the type of the function `f` when specialized for `i` at position
* `pos` at path `path`
*/
pragma[nomagic]
Type assocFunctionTypeAt(Function f, ImplOrTraitItemNode i, FunctionPosition pos, TypePath path) {
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I think getAssocFunctionTypeAt would be a better name.

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The rewrite does not appear to be semantics preserving; If you make a copy of the old FunctionType.qll library, rename it to FunctionTypeOld.qll and add

pragma[nomagic]
Type assocFunctionTypeAt(Function f, ImplOrTraitItemNode i, FunctionPosition pos, TypePath path) {
  exists(AssocFunctionType at |
    at.appliesTo(f, pos, i) and
    result = at.getDeclaredTypeAt(path)
  )
}

Then the two debug predicates below both have rows when I quick-eval:

private import FunctionTypeOld as Old

private Type testassocFunctionTypeAtMissing(
  Function f, ImplOrTraitItemNode i, FunctionPosition pos, TypePath path
) {
  not result = assocFunctionTypeAt(f, i, pos, path) and
  result = Old::assocFunctionTypeAt(f, i, pos, path)
}

private Type testassocFunctionTypeAtExtra(
  Function f, ImplOrTraitItemNode i, FunctionPosition pos, TypePath path
) {
  result = assocFunctionTypeAt(f, i, pos, path) and
  not result = Old::assocFunctionTypeAt(f, i, pos, path)
}

(You will also need to replace the existing FunctionPosition class with an alias for Old::FunctionPosition).

exists(MkAssocFunctionType(f, i, pos)) and
(
// No specialization needed when the function is directly in the trait or
// impl block or the declared type is not a type parameter
(i.getAnAssocItem() = f or not result instanceof TypeParameter) and
result = pos.getTypeMention(f).resolveTypeAt(path)
or
not i.getAnAssocItem() = f and
exists(TypePath prefix, TypePath suffix, TypeParameter tp |
path = prefix.append(suffix) and
tp = pos.getTypeMention(f).resolveTypeAt(prefix)
|
parent = i.(ImplItemNode).resolveTraitTy() and
parentMention = i.(ImplItemNode).getTraitPath()
or
parent = i.(TraitItemNode).resolveBound(parentMention)
if tp = TSelfTypeParameter(_)
then result = resolveImplOrTraitType(i, suffix)
else
exists(TraitItemNode trait, TypeMention condition, TypeMention constraint |
trait.getAnAssocItem() = f and
BaseTypes::rootTypesSatisfaction(_, TTrait(trait), _, condition, constraint) and
result = traitConstraintTypeAt(condition, constraint, tp, suffix)
|
condition = i.(Trait) or condition = i.(Impl).getSelfTy()
)
)
}
)
}

/**
* The type of an associated function at a given position, when viewed as a member
* of a given trait or `impl` block.
* The type of an associated function at a given position, when its implicit
* `Self` type parameter is specialized to a given trait or `impl` block.
*
* Example:
*
Expand Down Expand Up @@ -126,64 +152,13 @@ private newtype TAssocFunctionType =
* `self4` | `impl T2 for X` | `X`
* `self5` | `impl T2 for X` | `X`
*/
class AssocFunctionType extends TAssocFunctionType {
private predicate isFunctionType(Function f, FunctionPosition pos, ImplOrTraitItemNode i) {
this = MkAssocFunctionType(f, pos, i)
}

private predicate isInheritedFunctionType(
Function f, FunctionPosition pos, TypeMention parentMention, TraitItemNode parent,
ImplOrTraitItemNode i
) {
this = MkInheritedAssocFunctionType(f, pos, parentMention, parent, i)
}

class AssocFunctionType extends MkAssocFunctionType {
/**
* Holds if this function type applies to the function `f` at position `pos`,
* when viewed as a member of the `impl` or trait item `i`.
*/
predicate appliesTo(Function f, FunctionPosition pos, ImplOrTraitItemNode i) {
this.isFunctionType(f, pos, i)
or
this.isInheritedFunctionType(f, pos, _, _, i)
}

/** Gets the type at the given path. */
pragma[nomagic]
Type getDeclaredTypeAt(TypePath path) {
exists(Function f, FunctionPosition pos |
this.isFunctionType(f, pos, _) and
result = pos.getTypeMention(f).resolveTypeAt(path)
)
or
exists(
Function f, FunctionPosition pos, TypeMention parentMention, TraitItemNode parent,
AssocFunctionType parentType, ImplOrTraitItemNode i
|
this.isInheritedFunctionType(f, pos, parentMention, parent, i) and
parentType.appliesTo(f, pos, parent)
|
result = parentType.getDeclaredTypeAt(path) and
not result instanceof TypeParameter
or
exists(TypePath prefix, TypePath suffix | path = prefix.append(suffix) |
parentType.hasSelfTypeParameterAt(prefix) and
result = resolveImplOrTraitType(i, suffix)
or
exists(TypeParameter tp |
tp = parentType.getTypeParameterAt(prefix) and
result = parentMention.resolveTypeAt(TypePath::singleton(tp).appendInverse(suffix))
)
)
)
}

pragma[nomagic]
private TypeParameter getTypeParameterAt(TypePath path) { result = this.getDeclaredTypeAt(path) }

pragma[nomagic]
private predicate hasSelfTypeParameterAt(TypePath path) {
this.getTypeParameterAt(path) = TSelfTypeParameter(_)
predicate appliesTo(Function f, ImplOrTraitItemNode i, FunctionPosition pos) {
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I changed the parameter order here to match assocFunctionTypeAt.

this = MkAssocFunctionType(f, i, pos)
}

/**
Expand All @@ -196,7 +171,10 @@ class AssocFunctionType extends TAssocFunctionType {
* traits when matching.
*/
Type getTypeAt(TypePath path) {
exists(Type t | t = this.getDeclaredTypeAt(path) |
exists(Function f, FunctionPosition pos, ImplOrTraitItemNode i, Type t |
this.appliesTo(f, i, pos) and
t = assocFunctionTypeAt(f, i, pos, path)
|
not t instanceof SelfTypeParameter and
result = t
or
Expand All @@ -206,7 +184,7 @@ class AssocFunctionType extends TAssocFunctionType {

private TypeMention getTypeMention() {
exists(Function f, FunctionPosition pos |
this.appliesTo(f, pos, _) and
this.appliesTo(f, _, pos) and
result = pos.getTypeMention(f)
)
}
Expand All @@ -216,20 +194,6 @@ class AssocFunctionType extends TAssocFunctionType {
Location getLocation() { result = this.getTypeMention().getLocation() }
}

/**
* Holds if the type of the function `f` at position `pos` and path `path` inside
* `i` is `type`.
*/
pragma[nomagic]
predicate assocFunctionTypeAt(
Function f, ImplOrTraitItemNode i, FunctionPosition pos, TypePath path, Type type
) {
exists(AssocFunctionType aft |
aft.appliesTo(f, pos, i) and
type = aft.getDeclaredTypeAt(path)
)
}

private Trait getALookupTrait(Type t) {
result = t.(TypeParamTypeParameter).getTypeParam().(TypeParamItemNode).resolveABound()
or
Expand Down
2 changes: 1 addition & 1 deletion shared/typeinference/codeql/typeinference/internal/TypeInference.qll
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Expand Up @@ -717,7 +717,7 @@ module Make1<LocationSig Location, InputSig1<Location> Input1> {
}

/** Provides logic related to base types. */
private module BaseTypes {
module BaseTypes {
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Making BaseTypes public was the simples way to get the needed predicates. We could also more surgically export the needed functions, but I'm not sure if that's worth the trouble.

/**
* Holds if, when `tm1` is considered an instantiation of `tm2`, then at
* the type parameter `tp` it has the type `t` at `path`.
Expand Down
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