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Infer bounded type for untyped int literals in comparisons #1016

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Infer bounded type for untyped int literals in comparisons #1016

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24 changes: 24 additions & 0 deletions src/main/scala/viper/gobra/frontend/info/implementation/typing/ExprTyping.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1018,6 +1018,18 @@ trait ExprTyping extends BaseTyping { this: TypeInfoImpl =>
case c => Violation.violation(s"This case should be unreachable, but got $c")
}

// If expr is an operand of a comparison whose other operand has a bounded integer type,
// pin expr's context type to that bounded type. This mirrors Go's implicit conversion of
// untyped constants in comparisons and avoids mixed-sort operands reaching later stages.
case cmp: PEquals => boundedCtxFromComparison(cmp.left, cmp.right, expr)
case cmp: PUnequals => boundedCtxFromComparison(cmp.left, cmp.right, expr)
case cmp: PLess => boundedCtxFromComparison(cmp.left, cmp.right, expr)
case cmp: PAtMost => boundedCtxFromComparison(cmp.left, cmp.right, expr)
case cmp: PGreater => boundedCtxFromComparison(cmp.left, cmp.right, expr)
case cmp: PAtLeast => boundedCtxFromComparison(cmp.left, cmp.right, expr)
case cmp: PGhostEquals => boundedCtxFromComparison(cmp.left, cmp.right, expr)
case cmp: PGhostUnequals => boundedCtxFromComparison(cmp.left, cmp.right, expr)

// expr has the default type if it appears in any other kind of statement
case x if x.isInstanceOf[PStatement] => Some(DEFAULT_INTEGER_TYPE)

Expand Down Expand Up @@ -1059,6 +1071,18 @@ trait ExprTyping extends BaseTyping { this: TypeInfoImpl =>
}
}

private def boundedCtxFromComparison(
left: PExpressionOrType,
right: PExpressionOrType,
expr: PExpression): Option[Type] = {
val other: PExpressionOrType = if (left eq expr) right else left
val otherType = exprOrTypeType(other)
underlyingType(otherType) match {
case IntT(_: BoundedIntegerKind) => Some(otherType)
case _ => None
}
}

def getBlankIdType(b: PBlankIdentifier): Type = b match {
case tree.parent(p) => p match {
case PAssignment(right, left) => getBlankAssigneeType(b, left, right)
Expand Down
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