Rust: Model async return types as dyn Future

Author: hvitved

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

@@ -520,7 +520,7 @@ private predicate typeEquality(AstNode n1, TypePath prefix1, AstNode n2, TypePat
     n2 = be.getStmtList().getTailExpr() and
     if be.isAsync()
     then
-      prefix1 = TypePath::singleton(getFutureOutputTypeParameter()) and
+      prefix1 = TypePath::singleton(getDynFutureOutputTypeParameter()) and
       prefix2.isEmpty()
     else (
       prefix1.isEmpty() and
@@ -940,7 +940,7 @@ private module CallExprBaseMatchingInput implements MatchingInputSig {
         or
         exists(TypePath suffix |
           result = this.resolveRetType(suffix) and
-          path = TypePath::cons(getFutureOutputTypeParameter(), suffix)
+          path = TypePath::cons(getDynFutureOutputTypeParameter(), suffix)
         )
       else result = this.resolveRetType(path)
     }
@@ -1426,16 +1426,22 @@ private Type inferLiteralType(LiteralExpr le, TypePath path, boolean certain) {
   certain = true
 }
 
+// always exists because of the mention in `builtins/mentions.rs`
 pragma[nomagic]
-private TraitType getFutureTraitType() { result.getTrait() instanceof FutureTrait }
+private DynTraitType getFutureTraitType() { result.getTrait() instanceof FutureTrait }
 
 pragma[nomagic]
 private AssociatedTypeTypeParameter getFutureOutputTypeParameter() {
   result.getTypeAlias() = any(FutureTrait ft).getOutputType()
 }
 
 pragma[nomagic]
-private TraitType inferAsyncBlockExprRootType(AsyncBlockExpr abe) {
+private DynTraitTypeParameter getDynFutureOutputTypeParameter() {
+  result = TDynTraitTypeParameter(any(FutureTrait ft).getOutputType())
+}
+
+pragma[nomagic]
+private DynTraitType inferAsyncBlockExprRootType(AsyncBlockExpr abe) {
   // `typeEquality` handles the non-root case
   exists(abe) and
   result = getFutureTraitType()
@@ -1773,7 +1779,7 @@ private Type inferClosureExprType(AstNode n, TypePath path) {
   exists(ClosureExpr ce |
     n = ce and
     path.isEmpty() and
-    result = TDynTraitType(any(FnOnceTrait t))
+    result = TDynTraitType(any(FnOnceTrait t)) // always exists because of the mention in `builtins/mentions.rs`
     or
     n = ce and
     path = TypePath::singleton(TDynTraitTypeParameter(any(FnOnceTrait t).getTypeParam())) and

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

@@ -3728,9 +3728,9 @@ inferType
 | main.rs:1915:25:1917:5 | { ... } |  | main.rs:1909:5:1909:14 | S1 |
 | main.rs:1916:9:1916:10 | S1 |  | main.rs:1909:5:1909:14 | S1 |
 | main.rs:1919:41:1921:5 | { ... } |  | main.rs:1919:16:1919:39 | ImplTraitTypeRepr |
-| main.rs:1920:9:1920:20 | { ... } |  | {EXTERNAL LOCATION} | trait Future |
+| main.rs:1920:9:1920:20 | { ... } |  | {EXTERNAL LOCATION} | dyn Future |
 | main.rs:1920:9:1920:20 | { ... } |  | main.rs:1919:16:1919:39 | ImplTraitTypeRepr |
-| main.rs:1920:9:1920:20 | { ... } | Output | main.rs:1909:5:1909:14 | S1 |
+| main.rs:1920:9:1920:20 | { ... } | dyn(Output) | main.rs:1909:5:1909:14 | S1 |
 | main.rs:1920:17:1920:18 | S1 |  | main.rs:1909:5:1909:14 | S1 |
 | main.rs:1929:13:1929:42 | SelfParam |  | {EXTERNAL LOCATION} | Pin |
 | main.rs:1929:13:1929:42 | SelfParam | Ptr | file://:0:0:0:0 | & |
@@ -3745,22 +3745,22 @@ inferType
 | main.rs:1936:41:1938:5 | { ... } |  | main.rs:1936:16:1936:39 | ImplTraitTypeRepr |
 | main.rs:1937:9:1937:10 | S2 |  | main.rs:1923:5:1923:14 | S2 |
 | main.rs:1937:9:1937:10 | S2 |  | main.rs:1936:16:1936:39 | ImplTraitTypeRepr |
-| main.rs:1941:9:1941:12 | f1(...) |  | {EXTERNAL LOCATION} | trait Future |
-| main.rs:1941:9:1941:12 | f1(...) | Output | main.rs:1909:5:1909:14 | S1 |
+| main.rs:1941:9:1941:12 | f1(...) |  | {EXTERNAL LOCATION} | dyn Future |
+| main.rs:1941:9:1941:12 | f1(...) | dyn(Output) | main.rs:1909:5:1909:14 | S1 |
 | main.rs:1941:9:1941:18 | await ... |  | main.rs:1909:5:1909:14 | S1 |
 | main.rs:1942:9:1942:12 | f2(...) |  | main.rs:1919:16:1919:39 | ImplTraitTypeRepr |
 | main.rs:1942:9:1942:18 | await ... |  | main.rs:1909:5:1909:14 | S1 |
 | main.rs:1943:9:1943:12 | f3(...) |  | main.rs:1936:16:1936:39 | ImplTraitTypeRepr |
 | main.rs:1943:9:1943:18 | await ... |  | main.rs:1909:5:1909:14 | S1 |
 | main.rs:1944:9:1944:10 | S2 |  | main.rs:1923:5:1923:14 | S2 |
 | main.rs:1944:9:1944:16 | await S2 |  | main.rs:1909:5:1909:14 | S1 |
-| main.rs:1945:13:1945:13 | b |  | {EXTERNAL LOCATION} | trait Future |
-| main.rs:1945:13:1945:13 | b | Output | main.rs:1909:5:1909:14 | S1 |
-| main.rs:1945:17:1945:28 | { ... } |  | {EXTERNAL LOCATION} | trait Future |
-| main.rs:1945:17:1945:28 | { ... } | Output | main.rs:1909:5:1909:14 | S1 |
+| main.rs:1945:13:1945:13 | b |  | {EXTERNAL LOCATION} | dyn Future |
+| main.rs:1945:13:1945:13 | b | dyn(Output) | main.rs:1909:5:1909:14 | S1 |
+| main.rs:1945:17:1945:28 | { ... } |  | {EXTERNAL LOCATION} | dyn Future |
+| main.rs:1945:17:1945:28 | { ... } | dyn(Output) | main.rs:1909:5:1909:14 | S1 |
 | main.rs:1945:25:1945:26 | S1 |  | main.rs:1909:5:1909:14 | S1 |
-| main.rs:1946:9:1946:9 | b |  | {EXTERNAL LOCATION} | trait Future |
-| main.rs:1946:9:1946:9 | b | Output | main.rs:1909:5:1909:14 | S1 |
+| main.rs:1946:9:1946:9 | b |  | {EXTERNAL LOCATION} | dyn Future |
+| main.rs:1946:9:1946:9 | b | dyn(Output) | main.rs:1909:5:1909:14 | S1 |
 | main.rs:1946:9:1946:15 | await b |  | main.rs:1909:5:1909:14 | S1 |
 | main.rs:1957:15:1957:19 | SelfParam |  | file://:0:0:0:0 | & |
 | main.rs:1957:15:1957:19 | SelfParam | &T | main.rs:1956:5:1958:5 | Self [trait Trait1] |
@@ -4954,7 +4954,7 @@ inferType
 | main.rs:2565:5:2565:60 | ...::g(...) |  | main.rs:72:5:72:21 | Foo |
 | main.rs:2565:20:2565:38 | ...::Foo {...} |  | main.rs:72:5:72:21 | Foo |
 | main.rs:2565:41:2565:59 | ...::Foo {...} |  | main.rs:72:5:72:21 | Foo |
-| main.rs:2581:5:2581:15 | ...::f(...) |  | {EXTERNAL LOCATION} | trait Future |
+| main.rs:2581:5:2581:15 | ...::f(...) |  | {EXTERNAL LOCATION} | dyn Future |
 | pattern_matching.rs:13:26:133:1 | { ... } |  | {EXTERNAL LOCATION} | Option |
 | pattern_matching.rs:13:26:133:1 | { ... } | T | file://:0:0:0:0 | () |
 | pattern_matching.rs:14:9:14:13 | value |  | {EXTERNAL LOCATION} | Option |

rust/tools/builtins/mentions.rs

@@ -0,0 +1,6 @@
+// Type mentions required by type inference
+
+use std::future::Future;
+fn mention_dyn_future<T>(f: &dyn Future<Output = T>) {}
+
+fn mention_dyn_fn_once<F>(f: &dyn FnOnce() -> F) {}