Rust: Add metric and debug predicates for type that reach the length limit

Author: paldepind

rust/ql/lib/codeql/rust/internal/TypeInference.qll

@@ -127,6 +127,8 @@ private module Input1 implements InputSig1<Location> {
         tp0 order by kind, id1, id2
       )
   }
+
+  int getTypePathLimit() { result = 10 }
 }
 
 private import Input1
@@ -135,6 +137,8 @@ private module M1 = Make1<Location, Input1>;
 
 private import M1
 
+predicate getTypePathLimit = Input1::getTypePathLimit/0;
+
 class TypePath = M1::TypePath;
 
 module TypePath = M1::TypePath;
@@ -2217,8 +2221,9 @@ private module Debug {
   private Locatable getRelevantLocatable() {
     exists(string filepath, int startline, int startcolumn, int endline, int endcolumn |
       result.getLocation().hasLocationInfo(filepath, startline, startcolumn, endline, endcolumn) and
-      filepath.matches("%/sqlx.rs") and
-      startline = [56 .. 60]
+      // startline = [319 .. 326] and
+      startline = 325 and
+      filepath.matches("%/register_allocator.rs")
     )
   }
 
@@ -2227,6 +2232,11 @@ private module Debug {
     result = inferType(n, path)
   }
 
+  Type debugInferTypeForNodeAtLimit(AstNode n, TypePath path) {
+    result = inferType(n, path) and
+    exists(TypePath path0 | exists(inferType(n, path0)) and path0.length() = getTypePathLimit())
+  }
+
   Function debugResolveCallTarget(Call c) {
     c = getRelevantLocatable() and
     result = resolveCallTarget(c)
@@ -2265,6 +2275,10 @@ private module Debug {
     result = strictcount(Type t0 | t0 = inferType(n, path))
   }
 
+  predicate countTypesForNodeAtLimit(AstNode n, int c) {
+    c = strictcount(Type t, TypePath path | t = debugInferTypeForNodeAtLimit(n, path))
+  }
+
   predicate maxTypes(AstNode n, TypePath path, Type t, int c) {
     c = countTypesAtPath(n, path, t) and
     c = max(countTypesAtPath(_, _, _))

rust/ql/src/queries/summary/NodesWithTypeAtLenghtLimit.ql

@@ -0,0 +1,20 @@
+/**
+ * @name Nodes With Type At Length Limit
+ * @description Counts the number of AST nodes with a type at the type path length limit.
+ * @kind metric
+ * @id rust/summary/nodes-at-type-path-length-limit
+ * @tags summary
+ */
+
+import rust
+import codeql.rust.internal.TypeInference
+
+from int atLimit
+where
+  atLimit =
+    count(AstNode n, TypePath path |
+      exists(inferType(n, path)) and path.length() = getTypePathLimit()
+    |
+      n
+    )
+select atLimit