Rust: Add TupleStructPat.getStruct.

Author: geoffw0

rust/ql/lib/codeql/rust/elements/internal/TupleStructPatImpl.qll

@@ -34,6 +34,11 @@ module Impl {
       exists(this.getField(pragma[only_bind_into](pos)))
     }
 
+    /**
+     * Gets the struct matched by this pattern.
+     */
+    Struct getStruct() { result = PathResolution::resolvePath(this.getPath()) }
+
     /** Gets the tuple field that matches the `pos`th pattern of this pattern. */
     pragma[nomagic]
     TupleField getTupleField(int pos) {

rust/ql/lib/codeql/rust/frameworks/Poem.qll

@@ -16,8 +16,7 @@ private class PoemHandlerParam extends RemoteSource::Range {
     exists(TupleStructPat param, Type t |
       this.asPat().getPat() = param.getAField() and
       t = inferType(param) and
-      t.(StructType).asItemNode().(Addressable).getCanonicalPath() =
-        ["poem::web::query::Query", "poem::web::path::Path"]
+      param.getStruct().getCanonicalPath() = ["poem::web::query::Query", "poem::web::path::Path"]
     )
   }
 }