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C#: Fix false positives in cs/unchecked-return-value

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This commit is contained in:
Tom Hvitved
2019-07-29 17:32:21 -07:00
parent b6f3f7866b
commit 5c127ef20d
4 changed files with 11 additions and 3 deletions
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1
change-notes/1.22/analysis-csharp.md
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@@ -24,6 +24,7 @@
| Number of commits | No results | Query has been removed. |
| Poorly documented files with many authors | No results | Query has been removed. |
| Recent activity | No results | Query has been removed. |
| Unchecked return value (`cs/unchecked-return-value`) | Fewer false positive results | Method calls that are expression bodies of `void` callables (for example, the call to `Foo` in `void Bar() => Foo()`) are no longer considered to use the return value. |
## Changes to code extraction

9
csharp/ql/src/API Abuse/UncheckedReturnValue.ql
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@@ -89,7 +89,14 @@ predicate whitelist(Method m) {
}
class DiscardedMethodCall extends MethodCall {
DiscardedMethodCall() { this.getParent() instanceof ExprStmt }
DiscardedMethodCall() {
this.getParent() instanceof ExprStmt
or
exists(Callable c |
this = c.getExpressionBody() and
not c.canReturn(this)
)
}
string query() {
exists(Method m |

3
csharp/ql/src/semmle/code/csharp/Callable.qll
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@@ -209,7 +209,8 @@ class Callable extends DotNet::Callable, Parameterizable, ExprOrStmtParent, @cal
override predicate canReturn(DotNet::Expr e) {
exists(ReturnStmt ret | ret.getEnclosingCallable() = this | e = ret.getExpr())
or
e = getExpressionBody()
e = this.getExpressionBody() and
not this.getReturnType() instanceof VoidType
}
/** Holds if this callable can yield return the expression `e`. */

1
csharp/ql/test/query-tests/API Abuse/UncheckedReturnValue/UncheckedReturnValue.expected
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@@ -4,6 +4,5 @@
| UncheckedReturnValue.cs:109:9:109:17 | call to method M1 | Result of call to 'M1' is ignored, but 90% of calls to this method have their result used. |
| UncheckedReturnValue.cs:130:9:130:21 | call to method M2 | Result of call to 'M2' is ignored, but 90% of calls to this method have their result used. |
| UncheckedReturnValue.cs:142:9:142:20 | call to method M3 | Result of call to 'M3' is ignored, but 90% of calls to this method have their result used. |
| UncheckedReturnValue.cs:169:9:169:12 | call to method M1 | Result of call to 'M1' is ignored, but 90% of calls to this method have their result used. |
| UncheckedReturnValueBad.cs:29:9:29:20 | call to method DoPrint | Result of call to 'DoPrint' is ignored, but 90% of calls to this method have their result used. |
| UncheckedReturnValueBad.cs:36:13:36:40 | call to method Read | Result of call to 'Read' is ignored, but should always be checked. |