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C#: Improve unification logic to handle ref structs.

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This commit is contained in:
Michael Nebel
2025-01-03 15:00:42 +01:00
parent 5ddc37867e
commit cac1e04de8
1 changed files with 29 additions and 9 deletions
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38
csharp/ql/lib/semmle/code/csharp/Unification.qll
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@@ -522,16 +522,21 @@ module Gvn {
/** Provides definitions related to type unification. */
module Unification {
/** A type parameter that is compatible with any type. */
/** A type parameter that is compatible with any type except `ref struct`. */
class UnconstrainedTypeParameter extends TypeParameter {
UnconstrainedTypeParameter() { not exists(getATypeConstraint(this)) }
UnconstrainedTypeParameter() {
not exists(getATypeConstraint(this)) and not exists(getANegativeTypeConstraint(this))
}
}
/** A type parameter that is constrained. */
class ConstrainedTypeParameter extends TypeParameter {
int constraintCount;
ConstrainedTypeParameter() { constraintCount = strictcount(getATypeConstraint(this)) }
ConstrainedTypeParameter() {
constraintCount = count(getATypeConstraint(this)) + count(getANegativeTypeConstraint(this)) and
constraintCount > 0
}
/**
* Holds if this type parameter is unifiable with type `t`.
@@ -559,7 +564,7 @@ module Unification {
bindingset[this]
pragma[inline_late]
override predicate unifiable(Type t) {
exists(TTypeParameterConstraint ttc | ttc = getATypeConstraint(this) |
forall(TTypeParameterConstraint ttc | ttc = getATypeConstraint(this) |
ttc = TRefTypeConstraint() and
t.isRefType()
or
@@ -567,13 +572,14 @@ module Unification {
t.isValueType()
or
typeConstraintUnifiable(ttc, t)
)
) and
(t.isRefLikeType() implies getANegativeTypeConstraint(this) = TAllowRefTypeConstraint())
}
bindingset[this]
pragma[inline_late]
override predicate subsumes(Type t) {
exists(TTypeParameterConstraint ttc | ttc = getATypeConstraint(this) |
forall(TTypeParameterConstraint ttc | ttc = getATypeConstraint(this) |
ttc = TRefTypeConstraint() and
t.isRefType()
or
@@ -581,7 +587,8 @@ module Unification {
t.isValueType()
or
typeConstraintSubsumes(ttc, t)
)
) and
(t.isRefLikeType() implies getANegativeTypeConstraint(this) = TAllowRefTypeConstraint())
}
}
@@ -603,7 +610,8 @@ module Unification {
t.isValueType()
or
typeConstraintUnifiable(ttc, t)
)
) and
(t.isRefLikeType() implies getANegativeTypeConstraint(this) = TAllowRefTypeConstraint())
}
bindingset[this]
@@ -617,7 +625,8 @@ module Unification {
t.isValueType()
or
typeConstraintSubsumes(ttc, t)
)
) and
(t.isRefLikeType() implies getANegativeTypeConstraint(this) = TAllowRefTypeConstraint())
}
}
@@ -632,6 +641,9 @@ module Unification {
not t instanceof TypeParameter
}
cached
newtype TTypeParameterNegativeConstraint = TAllowRefTypeConstraint()
cached
TTypeParameterConstraint getATypeConstraint(TypeParameter tp) {
exists(TypeParameterConstraints tpc | tpc = tp.getConstraints() |
@@ -650,6 +662,14 @@ module Unification {
)
}
cached
TTypeParameterNegativeConstraint getANegativeTypeConstraint(TypeParameter tp) {
exists(TypeParameterConstraints tpc | tpc = tp.getConstraints() |
tpc.hasAllowRefLikeTypeConstraint() and
result = TAllowRefTypeConstraint()
)
}
cached
predicate typeConstraintUnifiable(TTypeConstraint ttc, Type t) {
exists(Type t0 | ttc = TTypeConstraint(t0) | implicitConversionRestricted(t, t0))