Rust: Add expressions with known type metric

rust/ql/src/change-notes/2025-10-21-database-quality-diagnostic.md

@@ -0,0 +1,4 @@
+---
+category: minorAnalysis
+---
+* The "Low Rust analysis quality" query (`rust/diagnostic/database-quality`), used by the tool status page, has been extended with a measure of successful type inference.

rust/ql/src/queries/telemetry/DatabaseQuality.qll

@@ -6,6 +6,7 @@
 
 import rust
 import codeql.util.ReportStats
+import codeql.rust.internal.TypeInference as TypeInference
 
 module CallTargetStats implements StatsSig {
   int getNumberOfOk() { result = count(CallExprBase c | exists(c.getStaticTarget())) }
@@ -41,6 +42,20 @@ module MacroCallTargetStats implements StatsSig {
   string getNotOkText() { result = "macro calls with missing call target" }
 }
 
+private predicate hasGoodType(Expr e) { exists(TypeInference::inferType(e, _)) }
+
+module ExprTypeStats implements StatsSig {
+  int getNumberOfOk() { result = count(Expr e | e.fromSource() and hasGoodType(e)) }
+
+  int getNumberOfNotOk() { result = count(Expr e | e.fromSource() and not hasGoodType(e)) }
+
+  string getOkText() { result = "expressions with known type" }
+
+  string getNotOkText() { result = "expressions with unknown type" }
+}
+
 module CallTargetStatsReport = ReportStats<CallTargetStats>;
 
 module MacroCallTargetStatsReport = ReportStats<MacroCallTargetStats>;
+
+module ExprTypeStatsReport = ReportStats<ExprTypeStats>;

rust/ql/src/queries/telemetry/DatabaseQualityDiagnostics.ql

@@ -13,6 +13,8 @@ private predicate diagnostic(string msg, float value, float threshold) {
   CallTargetStatsReport::percentageOfOk(msg, value) and threshold = 50
   or
   MacroCallTargetStatsReport::percentageOfOk(msg, value) and threshold = 50
+  or
+  ExprTypeStatsReport::percentageOfOk(msg, value) and threshold = 20
 }
 
 private string getDbHealth() {

rust/ql/src/queries/telemetry/ExtractorInformation.ql

@@ -54,7 +54,10 @@ where
     CallTargetStatsReport::percentageOfOk(key, value) or
     MacroCallTargetStatsReport::numberOfOk(key, value) or
     MacroCallTargetStatsReport::numberOfNotOk(key, value) or
-    MacroCallTargetStatsReport::percentageOfOk(key, value)
+    MacroCallTargetStatsReport::percentageOfOk(key, value) or
+    ExprTypeStatsReport::numberOfOk(key, value) or
+    ExprTypeStatsReport::numberOfNotOk(key, value) or
+    ExprTypeStatsReport::percentageOfOk(key, value)
   ) and
   /* Infinity */
   value != 1.0 / 0.0 and