Rust: Fix bad join

[hvitved]

#19584 follow-up. The bad join appears to only happen when running the SummaryStats.ql query.

[2025-06-10 15:21:37] (83s) Tuple counts for TypeMention::PathTypeReprMention.aliasResolveTypeAt/1#dispred#ae16f47b#fbf#cpe#13/2@i5#5a5451wi after 57.7s:
                      205999      ~1028%     {3} r1 = JOIN `TypeMention::TypeMention.resolveTypeAt/1#dispred#a125c821#bff#reorder_1_0_2#prev_delta` WITH `_TypeAlias::Generated::TypeAlias.getTypeRepr/0#dispred#5fd7e521_TypeMention::PathTypeReprMention#a35__#join_rhs#1` ON FIRST 2 OUTPUT Rhs.2, Lhs.2 'result', Rhs.3 'this'
                                             {3}    | AND NOT `project#TypeMention::pathGetTypeParameter/2#fd301eed#2`(FIRST 2)
                      204000      ~982%      {2}    | SCAN OUTPUT In.2 'this', In.1 'result'

                      5499        ~448%      {7} r2 = JOIN `TypeMention::TypeMention.resolveTypeAt/1#dispred#a125c821#bff#reorder_0_2_1#prev_delta` WITH `_GenericArgList::GenericArgList.getTypeArg/1#dispred#1c780027_PathSegment::Generated::PathSegment.ge__#join_rhs#1` ON FIRST 1 OUTPUT Rhs.1, Rhs.2 'this', Rhs.3, Lhs.1 'result', _, Lhs.2, _
                                             {5}    | REWRITE WITH Tmp.4 := "", Tmp.6 := "", Out.4 := InverseAppend(Tmp.4,In.5,Tmp.6) KEEPING 5
                      2500        ~398%      {5}    | SCAN OUTPUT In.0, In.2, In.4, In.1 'this', In.3 'result'
                      0           ~0%        {2}    | JOIN WITH `TypeMention::TypeMention.resolveTypeAt/1#dispred#a125c821#bff#reorder_0_2_1#prev` ON FIRST 3 OUTPUT Lhs.3 'this', Lhs.4 'result'

                      9000        ~489%      {7} r3 = JOIN `TypeMention::TypeMention.resolveTypeAt/1#dispred#a125c821#bff#reorder_0_2_1#prev_delta` WITH `_PathSegment::Generated::PathSegment.getGenericArgList/0#dispred#e072653b__Path::Generated::Path.get__#join_rhs#1` ON FIRST 1 OUTPUT Rhs.1, Rhs.2 'this', Rhs.3, Lhs.1, _, Lhs.2, _
                                             {5}    | REWRITE WITH Tmp.4 := "", Tmp.6 := "", Out.4 := InverseAppend(In.5,Tmp.4,Tmp.6) KEEPING 5
                      5000        ~411%      {5}    | SCAN OUTPUT In.4, In.0, In.1 'this', In.2, In.3
                      10461919500 ~610%      {6}    | JOIN WITH `TypeMention::TypeMention.resolveTypeAt/1#dispred#a125c821#bff#reorder_1_0_2#prev` ON FIRST 1 OUTPUT Lhs.3, Rhs.1, Lhs.1, Lhs.2 'this', Lhs.4, Rhs.2 'result'
                      500         ~0%        {5}    | JOIN WITH `GenericArgList::GenericArgList.getTypeArg/1#dispred#1c780027_021#join_rhs` ON FIRST 2 OUTPUT Lhs.2, Rhs.2, Lhs.4, Lhs.3 'this', Lhs.5 'result'
                      0           ~0%        {2}    | JOIN WITH `TypeMention::pathGetTypeParameter/2#fd301eed` ON FIRST 3 OUTPUT Lhs.3 'this', Lhs.4 'result'

                      204000      ~982%      {2} r4 = r1 UNION r2 UNION r3
                      203964      ~982%      {2}    | AND NOT `TypeMention::PathTypeReprMention.aliasResolveTypeAt/1#dispred#ae16f47b#fbf#cpe#13#prev`(FIRST 2)
                                             return r4

DCA reports an average 75 % analysis time speedup.

[Copilot]

Pull Request Overview

This PR adds pragma[nomagic] annotations to two methods in the Rust CodeQL QLL files to improve join behavior when running the SummaryStats.ql query.

• Add pragma[nomagic] to PathTypeReprMention.aliasResolveTypeAt
• Add pragma[nomagic] to GenericArgListImpl.getTypeArg

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
rust/ql/lib/codeql/rust/internal/TypeMention.qll	Insert pragma[nomagic] before aliasResolveTypeAt
rust/ql/lib/codeql/rust/elements/internal/GenericArgListImpl.qll	Insert pragma[nomagic] before getTypeArg

Comments suppressed due to low confidence (2)

rust/ql/lib/codeql/rust/internal/TypeMention.qll:133

• The Javadoc comment above aliasResolveTypeAt is now separated from the method by the pragma. This may prevent the comment from being associated with the method in generated docs—consider moving the comment block above the pragma or placing the pragma before the comment.

pragma[nomagic]

rust/ql/lib/codeql/rust/elements/internal/GenericArgListImpl.qll:29

• The documentation comment for getTypeArg is now separated by the pragma, which may break its association with the method. Consider relocating the pragma or the comment so that the doc block immediately precedes the method signature.

pragma[nomagic]