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C#: Proper handling of value tuples in cs/call-to-object-tostring. #18849

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Merged
michaelnebel merged 4 commits into from
Feb 25, 2025
Merged

C#: Proper handling of value tuples in cs/call-to-object-tostring. #18849

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5eb305d
C#: Add some value tuple examples for cs/call-to-object-tostring and …
michaelnebel Feb 24, 2025
a85131b
C#: Better handling of (value) tuple types in cs/call-to-object-tostr…
michaelnebel Feb 24, 2025
97f9f0c
C#: Update test expected output.
michaelnebel Feb 24, 2025
e8f86e4
C#: Add change note.
michaelnebel Feb 24, 2025
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6 changes: 6 additions & 0 deletions csharp/ql/src/Useless code/DefaultToStringQuery.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,7 @@ private predicate alwaysInvokesToString(ParameterRead pr) {
* method from `System.Object` or `System.ValueType`.
*/
predicate alwaysDefaultToString(ValueOrRefType t) {
not t instanceof TupleType and
exists(ToStringMethod m | t.hasMethod(m) |
m.getDeclaringType() instanceof SystemObjectClass or
m.getDeclaringType() instanceof SystemValueTypeClass
Expand All @@ -55,6 +56,11 @@ predicate alwaysDefaultToString(ValueOrRefType t) {
overriding.getABaseType+() = t
) and
((t.isAbstract() or t instanceof Interface) implies not t.isEffectivelyPublic())
or
exists(ValueOrRefType elem |
elem = t.(TupleType).getElementType(_) and
alwaysDefaultToString(elem)
)
}

class DefaultToStringType extends ValueOrRefType {
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4 changes: 4 additions & 0 deletions csharp/ql/src/change-notes/2025-02-24-object-tostring.md
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@@ -0,0 +1,4 @@
---
category: minorAnalysis
---
* C#: Improve precision of the query `cs/call-to-object-tostring` for value tuples.
10 changes: 10 additions & 0 deletions csharp/ql/test/query-tests/Useless Code/DefaultToString/DefaultToString.cs
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Expand Up @@ -35,6 +35,16 @@ void M()

IPublic g = null;
Console.WriteLine(g); // GOOD

Console.WriteLine(new ValueTuple<int, int>(1, 2)); // GOOD

Console.WriteLine((1, 2)); // GOOD

var t1 = new ValueTuple<int, DefaultToString>(1, new DefaultToString());
Console.WriteLine(t1); // BAD

var t2 = new ValueTuple<A, D>(new A(), new D());
Console.WriteLine(t2); // GOOD
}

class A
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3 changes: 2 additions & 1 deletion csharp/ql/test/query-tests/Useless Code/DefaultToString/DefaultToString.expected
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Expand Up @@ -2,7 +2,8 @@
| DefaultToString.cs:10:28:10:28 | access to local variable d | Default 'ToString()': $@ inherits 'ToString()' from 'Object', and so is not suitable for printing. | DefaultToString.cs:4:14:4:28 | DefaultToString | DefaultToString |
| DefaultToString.cs:16:27:16:30 | access to local variable ints | Default 'ToString()': $@ inherits 'ToString()' from 'Object', and so is not suitable for printing. | file://:0:0:0:0 | Int32[] | Int32[] |
| DefaultToString.cs:19:24:19:27 | access to local variable ints | Default 'ToString()': $@ inherits 'ToString()' from 'Object', and so is not suitable for printing. | file://:0:0:0:0 | Int32[] | Int32[] |
| DefaultToString.cs:34:27:34:27 | access to local variable f | Default 'ToString()': $@ inherits 'ToString()' from 'Object', and so is not suitable for printing. | DefaultToString.cs:62:23:62:30 | IPrivate | IPrivate |
| DefaultToString.cs:34:27:34:27 | access to local variable f | Default 'ToString()': $@ inherits 'ToString()' from 'Object', and so is not suitable for printing. | DefaultToString.cs:72:23:72:30 | IPrivate | IPrivate |
| DefaultToString.cs:44:27:44:28 | (...) ... | Default 'ToString()': $@ inherits 'ToString()' from 'Object', and so is not suitable for printing. | file://:0:0:0:0 | (Int32,DefaultToString) | (Int32,DefaultToString) |
| DefaultToStringBad.cs:8:35:8:35 | access to local variable p | Default 'ToString()': $@ inherits 'ToString()' from 'Object', and so is not suitable for printing. | DefaultToStringBad.cs:14:11:14:16 | Person | Person |
| DefaultToStringBad.cs:11:38:11:41 | access to local variable ints | Default 'ToString()': $@ inherits 'ToString()' from 'Object', and so is not suitable for printing. | file://:0:0:0:0 | Int32[] | Int32[] |
| WriteLineArray.cs:7:23:7:26 | access to parameter args | Default 'ToString()': $@ inherits 'ToString()' from 'Object', and so is not suitable for printing. | file://:0:0:0:0 | String[] | String[] |
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