Rust: Add inline expectations test for type inference

Author: paldepind

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

@@ -5,6 +5,7 @@
  */
 
 private import codeql.rust.elements.internal.generated.Function
+private import codeql.rust.elements.Comment
 
 /**
  * INTERNAL: This module contains the customizable definition of `Function` and should not
@@ -26,5 +27,22 @@ module Impl {
    */
   class Function extends Generated::Function {
     override string toStringImpl() { result = "fn " + this.getName().getText() }
+
+    /**
+     * Gets a comment preceding this function.
+     *
+     * A comment is considered preceding if it occurs immediately before this
+     * function or if only other comments occur between the comment and this
+     * function.
+     */
+    Comment getPrecedingComment() {
+      result.getLocation().getFile() = this.getLocation().getFile() and
+      // When a function is preceded by comments its start line is the line of
+      // the first comment. Hence all relevant comments are found by including
+      // comments from the start line and up to the line with the function
+      // name.
+      this.getLocation().getStartLine() <= result.getLocation().getStartLine() and
+      result.getLocation().getStartLine() <= this.getName().getLocation().getStartLine()
+    }
   }
 }

rust/ql/lib/utils/test/InlineMadTest.qll

@@ -5,16 +5,7 @@ private module InlineMadTestLang implements InlineMadTestLangSig {
   class Callable = R::Function;
 
   string getComment(R::Function callable) {
-    exists(R::Comment comment |
-      result = comment.getCommentText() and
-      comment.getLocation().getFile() = callable.getLocation().getFile() and
-      // When a function is preceded by comments its start line is the line of
-      // the first comment. Hence all relevant comments are found by including
-      // comments from the start line and up to the line with the function
-      // name.
-      callable.getLocation().getStartLine() <= comment.getLocation().getStartLine() and
-      comment.getLocation().getStartLine() <= callable.getName().getLocation().getStartLine()
-    )
+    result = callable.getPrecedingComment().getCommentText()
   }
 }
 

rust/ql/test/library-tests/type-inference/loop/main.rs

@@ -9,6 +9,6 @@ trait T1<T>: T2<S<T>> {
 
 trait T2<T>: T1<S<T>> {
     fn bar(self) {
-        self.foo()
+        self.foo() // $ method=foo
     }
 }