Rust: Fix bad join

Author: Private Tech Event

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

@@ -4,6 +4,7 @@
  * INTERNAL: Do not use.
  */
 
+private import codeql.files.FileSystem
 private import codeql.rust.elements.internal.generated.Function
 private import codeql.rust.elements.Comment
 
@@ -28,6 +29,30 @@ module Impl {
  class Function extends Generated::Function {
  override string toStringImpl() { result = "fn " + this.getName().getText() }
 
+ pragma[nomagic]
+ private predicate hasPotentialCommentAt(File f, int line) {
+ f = 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.
+ line in [this.getLocation().getStartLine() .. this.getName().getLocation().getStartLine()]
+ }
+
+ /**
+ * 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 getAPrecedingComment() {
+ exists(File f, int line |
+ this.hasPotentialCommentAt(f, line) and
+ result.getLocation().hasLocationFileInfo(f, line, _, _, _)
+ )
+ }
+
  /**
  * Gets a comment preceding this function.
  *

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

@@ -5,7 +5,7 @@ private module InlineMadTestLang implements InlineMadTestLangSig {
  class Callable = R::Function;
 
  string getComment(R::Function callable) {
- result = callable.getPrecedingComment().getCommentText()
+ result = callable.getAPrecedingComment().getCommentText()
  }
 }
 

rust/ql/test/library-tests/type-inference/type-inference.ql

@@ -11,9 +11,9 @@ module ResolveTest implements TestSig {
  string getARelevantTag() { result = ["method", "fieldof"] }
 
  private predicate functionHasValue(Function f, string value) {
- f.getPrecedingComment().getCommentText() = value
+ f.getAPrecedingComment().getCommentText() = value
  or
- not exists(f.getPrecedingComment()) and
+ not exists(f.getAPrecedingComment()) and
  value = f.getName().getText()
  }