Rust: Type inference for ? expressions

Author: hvitved

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

@@ -6,6 +6,7 @@ private import Type
 private import Type as T
 private import TypeMention
 private import codeql.typeinference.internal.TypeInference
+private import codeql.rust.frameworks.stdlib.Stdlib
 
 class Type = T::Type;
 
@@ -891,6 +892,17 @@ private Type inferRefExprType(Expr e, TypePath path) {
   )
 }
 
+pragma[nomagic]
+private Type inferTryExprType(TryExpr te, TypePath path) {
+  exists(TypeParam tp |
+    result = inferType(te.getExpr(), TypePath::cons(TTypeParamTypeParameter(tp), path))
+  |
+    tp = any(ResultEnum r).getGenericParamList().getGenericParam(0)
+    or
+    tp = any(OptionEnum o).getGenericParamList().getGenericParam(0)
+  )
+}
+
 cached
 private module Cached {
   private import codeql.rust.internal.CachedStages
@@ -1008,6 +1020,8 @@ private module Cached {
     result = inferFieldExprType(n, path)
     or
     result = inferRefExprType(n, path)
+    or
+    result = inferTryExprType(n, path)
   }
 }
 

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

@@ -957,22 +957,22 @@ mod try_expressions {
 
     // Simple function using ? operator with same error types
     fn try_same_error() -> Result<S1, S1> {
-        let x = Result::Ok(S1)?; // $ MISSING: type=x:S1
+        let x = Result::Ok(S1)?; // $ type=x:S1
         Result::Ok(S1)
     }
 
     // Function using ? operator with different error types that need conversion
     fn try_convert_error() -> Result<S1, S2> {
         let x = Result::Ok(S1);
-        let y = x?; // $ MISSING: type=y:S1
+        let y = x?; // $ type=y:S1
         Result::Ok(S1)
     }
 
     // Chained ? operations
     fn try_chained() -> Result<S1, S2> {
         let x = Result::Ok(Result::Ok(S1));
         // First ? returns Result<S1, S2>, second ? returns S1
-        let y = x?.map(|s| s)?; // $ MISSING: method=map
+        let y = x?.map(|s| s)?; // $ method=map
         Result::Ok(S1)
     }
 

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

@@ -1018,8 +1018,10 @@ inferType
 | main.rs:959:43:962:5 | { ... } |  | file://:0:0:0:0 | Result |
 | main.rs:959:43:962:5 | { ... } | E | main.rs:952:5:953:14 | S1 |
 | main.rs:959:43:962:5 | { ... } | T | main.rs:952:5:953:14 | S1 |
+| main.rs:960:13:960:13 | x |  | main.rs:952:5:953:14 | S1 |
 | main.rs:960:17:960:30 | ...::Ok(...) |  | file://:0:0:0:0 | Result |
 | main.rs:960:17:960:30 | ...::Ok(...) | T | main.rs:952:5:953:14 | S1 |
+| main.rs:960:17:960:31 | TryExpr |  | main.rs:952:5:953:14 | S1 |
 | main.rs:960:28:960:29 | S1 |  | main.rs:952:5:953:14 | S1 |
 | main.rs:961:9:961:22 | ...::Ok(...) |  | file://:0:0:0:0 | Result |
 | main.rs:961:9:961:22 | ...::Ok(...) | E | main.rs:952:5:953:14 | S1 |
@@ -1033,8 +1035,10 @@ inferType
 | main.rs:966:17:966:30 | ...::Ok(...) |  | file://:0:0:0:0 | Result |
 | main.rs:966:17:966:30 | ...::Ok(...) | T | main.rs:952:5:953:14 | S1 |
 | main.rs:966:28:966:29 | S1 |  | main.rs:952:5:953:14 | S1 |
+| main.rs:967:13:967:13 | y |  | main.rs:952:5:953:14 | S1 |
 | main.rs:967:17:967:17 | x |  | file://:0:0:0:0 | Result |
 | main.rs:967:17:967:17 | x | T | main.rs:952:5:953:14 | S1 |
+| main.rs:967:17:967:18 | TryExpr |  | main.rs:952:5:953:14 | S1 |
 | main.rs:968:9:968:22 | ...::Ok(...) |  | file://:0:0:0:0 | Result |
 | main.rs:968:9:968:22 | ...::Ok(...) | E | main.rs:955:5:956:14 | S2 |
 | main.rs:968:9:968:22 | ...::Ok(...) | T | main.rs:952:5:953:14 | S1 |
@@ -1054,6 +1058,9 @@ inferType
 | main.rs:975:17:975:17 | x |  | file://:0:0:0:0 | Result |
 | main.rs:975:17:975:17 | x | T | file://:0:0:0:0 | Result |
 | main.rs:975:17:975:17 | x | T.T | main.rs:952:5:953:14 | S1 |
+| main.rs:975:17:975:18 | TryExpr |  | file://:0:0:0:0 | Result |
+| main.rs:975:17:975:18 | TryExpr | T | main.rs:952:5:953:14 | S1 |
+| main.rs:975:17:975:29 | ... .map(...) |  | file://:0:0:0:0 | Result |
 | main.rs:976:9:976:22 | ...::Ok(...) |  | file://:0:0:0:0 | Result |
 | main.rs:976:9:976:22 | ...::Ok(...) | E | main.rs:955:5:956:14 | S2 |
 | main.rs:976:9:976:22 | ...::Ok(...) | T | main.rs:952:5:953:14 | S1 |
@@ -1064,11 +1071,15 @@ inferType
 | main.rs:980:69:987:5 | { ... } |  | file://:0:0:0:0 | Result |
 | main.rs:980:69:987:5 | { ... } | E | main.rs:952:5:953:14 | S1 |
 | main.rs:980:69:987:5 | { ... } | T | main.rs:980:20:980:27 | T |
+| main.rs:981:13:981:17 | value |  | main.rs:980:20:980:27 | T |
 | main.rs:981:21:981:25 | input |  | file://:0:0:0:0 | Result |
 | main.rs:981:21:981:25 | input | E | main.rs:952:5:953:14 | S1 |
 | main.rs:981:21:981:25 | input | T | main.rs:980:20:980:27 | T |
+| main.rs:981:21:981:26 | TryExpr |  | main.rs:980:20:980:27 | T |
 | main.rs:982:22:982:38 | ...::Ok(...) |  | file://:0:0:0:0 | Result |
+| main.rs:982:22:982:38 | ...::Ok(...) | T | main.rs:980:20:980:27 | T |
 | main.rs:982:22:985:10 | ... .and_then(...) |  | file://:0:0:0:0 | Result |
+| main.rs:982:33:982:37 | value |  | main.rs:980:20:980:27 | T |
 | main.rs:982:53:985:9 | { ... } |  | file://:0:0:0:0 | Result |
 | main.rs:982:53:985:9 | { ... } | E | main.rs:952:5:953:14 | S1 |
 | main.rs:984:13:984:34 | ...::Ok::<...>(...) |  | file://:0:0:0:0 | Result |