Rust: Restrict type propagation into receivers

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

@@ -778,13 +778,6 @@ private predicate typeEquality(AstNode n1, TypePath prefix1, AstNode n2, TypePat
   prefix1 = TypePath::singleton(getArrayTypeParameter()) and
   prefix2.isEmpty()
   or
-  exists(Struct s |
-    n2 = [n1.(RangeExpr).getStart(), n1.(RangeExpr).getEnd()] and
-    prefix1 = TypePath::singleton(TTypeParamTypeParameter(s.getGenericParamList().getATypeParam())) and
-    prefix2.isEmpty() and
-    s = getRangeType(n1)
-  )
-  or
   exists(ClosureExpr ce, int index |
     n1 = ce and
     n2 = ce.getParam(index).getPat() and
@@ -829,6 +822,12 @@ private predicate lubCoercion(AstNode parent, AstNode child, TypePath prefix) {
   bodyReturns(parent, child) and
   strictcount(Expr e | bodyReturns(parent, e)) > 1 and
   prefix.isEmpty()
+  or
+  exists(Struct s |
+    child = [parent.(RangeExpr).getStart(), parent.(RangeExpr).getEnd()] and
+    prefix = TypePath::singleton(TTypeParamTypeParameter(s.getGenericParamList().getATypeParam())) and
+    s = getRangeType(parent)
+  )
 }
 
 /**
@@ -1031,10 +1030,10 @@ private module StructExprMatchingInput implements MatchingInputSig {
 private module StructExprMatching = Matching<StructExprMatchingInput>;
 
 pragma[nomagic]
-private Type inferStructExprType0(AstNode n, boolean isReturn, TypePath path) {
+private Type inferStructExprType0(AstNode n, FunctionPosition pos, TypePath path) {
   exists(StructExprMatchingInput::Access a, StructExprMatchingInput::AccessPosition apos |
     n = a.getNodeAt(apos) and
-    if apos.isStructPos() then isReturn = true else isReturn = false
+    if apos.isStructPos() then pos.isReturn() else pos.asPosition() = 0 // the actual position doesn't matter, as long as it is positional
   |
     result = StructExprMatching::inferAccessType(a, apos, path)
     or
@@ -1113,6 +1112,25 @@ private Trait getCallExprTraitQualifier(CallExpr ce) {
  * Provides functionality related to context-based typing of calls.
  */
 private module ContextTyping {
+  /**
+   * Holds if `f` mentions type parameter `tp` at some non-return position,
+   * possibly via a constraint on another mentioned type parameter.
+   */
+  pragma[nomagic]
+  private predicate assocFunctionMentionsTypeParameterAtNonRetPos(
+    ImplOrTraitItemNode i, Function f, TypeParameter tp
+  ) {
+    exists(FunctionPosition nonRetPos |
+      not nonRetPos.isReturn() and
+      tp = getAssocFunctionTypeAt(f, i, nonRetPos, _)
+    )
+    or
+    exists(TypeParameter mid |
+      assocFunctionMentionsTypeParameterAtNonRetPos(i, f, mid) and
+      tp = getATypeParameterConstraint(mid, _)
+    )
+  }
+
   /**
    * Holds if the return type of the function `f` inside `i` at `path` is type
    * parameter `tp`, and `tp` does not appear in the type of any parameter of
@@ -1129,12 +1147,7 @@ private module ContextTyping {
   ) {
     pos.isReturn() and
     tp = getAssocFunctionTypeAt(f, i, pos, path) and
-    not exists(FunctionPosition nonResPos | not nonResPos.isReturn() |
-      tp = getAssocFunctionTypeAt(f, i, nonResPos, _)
-      or
-      // `Self` types in traits implicitly mention all type parameters of the trait
-      getAssocFunctionTypeAt(f, i, nonResPos, _) = TSelfTypeParameter(i)
-    )
+    not assocFunctionMentionsTypeParameterAtNonRetPos(i, f, tp)
   }
 
   /**
@@ -1184,7 +1197,7 @@ private module ContextTyping {
   pragma[nomagic]
   private predicate hasUnknownType(AstNode n) { hasUnknownTypeAt(n, _) }
 
-  signature Type inferCallTypeSig(AstNode n, boolean isReturn, TypePath path);
+  signature Type inferCallTypeSig(AstNode n, FunctionPosition pos, TypePath path);
 
   /**
    * Given a predicate `inferCallType` for inferring the type of a call at a given
@@ -1194,19 +1207,34 @@ private module ContextTyping {
    */
   module CheckContextTyping<inferCallTypeSig/3 inferCallType> {
     pragma[nomagic]
-    private Type inferCallTypeFromContextCand(AstNode n, TypePath prefix, TypePath path) {
-      result = inferCallType(n, false, path) and
+    private Type inferCallNonReturnType(AstNode n, FunctionPosition pos, TypePath path) {
+      result = inferCallType(n, pos, path) and
+      not pos.isReturn()
+    }
+
+    pragma[nomagic]
+    private Type inferCallNonReturnType(
+      AstNode n, FunctionPosition pos, TypePath prefix, TypePath path
+    ) {
+      result = inferCallNonReturnType(n, pos, path) and
       hasUnknownType(n) and
       prefix = path.getAPrefix()
     }
 
     pragma[nomagic]
     Type check(AstNode n, TypePath path) {
-      result = inferCallType(n, true, path)
+      result = inferCallType(n, any(FunctionPosition pos | pos.isReturn()), path)
       or
-      exists(TypePath prefix |
-        result = inferCallTypeFromContextCand(n, prefix, path) and
+      exists(FunctionPosition pos, TypePath prefix |
+        result = inferCallNonReturnType(n, pos, prefix, path) and
         hasUnknownTypeAt(n, prefix)
+      |
+        pos.isPosition()
+        or
+        // Never propagate type information directly into the receiver, since its type
+        // must already have been known in order to resolve the call
+        pos.isSelf() and
+        not prefix.isEmpty()
       )
     }
   }
@@ -2607,12 +2635,9 @@ private Type inferMethodCallType0(
 }
 
 pragma[nomagic]
-private Type inferMethodCallTypeNonSelf(AstNode n, boolean isReturn, TypePath path) {
-  exists(MethodCallMatchingInput::AccessPosition apos |
-    result = inferMethodCallType0(_, apos, n, _, path) and
-    not apos.isSelf() and
-    if apos.isReturn() then isReturn = true else isReturn = false
-  )
+private Type inferMethodCallTypeNonSelf(AstNode n, FunctionPosition pos, TypePath path) {
+  result = inferMethodCallType0(_, pos, n, _, path) and
+  not pos.isSelf()
 }
 
 /**
@@ -2664,11 +2689,11 @@ private Type inferMethodCallTypeSelf(AstNode n, DerefChain derefChain, TypePath
   )
 }
 
-private Type inferMethodCallTypePreCheck(AstNode n, boolean isReturn, TypePath path) {
-  result = inferMethodCallTypeNonSelf(n, isReturn, path)
+private Type inferMethodCallTypePreCheck(AstNode n, FunctionPosition pos, TypePath path) {
+  result = inferMethodCallTypeNonSelf(n, pos, path)
   or
   result = inferMethodCallTypeSelf(n, DerefChain::nil(), path) and
-  isReturn = false
+  pos.isSelf()
 }
 
 /**
@@ -3301,14 +3326,11 @@ private module NonMethodCallMatchingInput implements MatchingInputSig {
 private module NonMethodCallMatching = Matching<NonMethodCallMatchingInput>;
 
 pragma[nomagic]
-private Type inferNonMethodCallType0(AstNode n, boolean isReturn, TypePath path) {
-  exists(NonMethodCallMatchingInput::Access a, NonMethodCallMatchingInput::AccessPosition apos |
-    n = a.getNodeAt(apos) and
-    if apos.isReturn() then isReturn = true else isReturn = false
-  |
-    result = NonMethodCallMatching::inferAccessType(a, apos, path)
+private Type inferNonMethodCallType0(AstNode n, FunctionPosition pos, TypePath path) {
+  exists(NonMethodCallMatchingInput::Access a | n = a.getNodeAt(pos) |
+    result = NonMethodCallMatching::inferAccessType(a, pos, path)
     or
-    a.hasUnknownTypeAt(apos, path) and
+    a.hasUnknownTypeAt(pos, path) and
     result = TUnknownType()
   )
 }
@@ -3379,11 +3401,10 @@ private module OperationMatchingInput implements MatchingInputSig {
 private module OperationMatching = Matching<OperationMatchingInput>;
 
 pragma[nomagic]
-private Type inferOperationType0(AstNode n, boolean isReturn, TypePath path) {
-  exists(OperationMatchingInput::Access a, OperationMatchingInput::AccessPosition apos |
-    n = a.getNodeAt(apos) and
-    result = OperationMatching::inferAccessType(a, apos, path) and
-    if apos.isReturn() then isReturn = true else isReturn = false
+private Type inferOperationType0(AstNode n, FunctionPosition pos, TypePath path) {
+  exists(OperationMatchingInput::Access a |
+    n = a.getNodeAt(pos) and
+    result = OperationMatching::inferAccessType(a, pos, path)
   )
 }
 
@@ -3716,11 +3737,13 @@ private module AwaitSatisfiesConstraintInput implements SatisfiesConstraintInput
   }
 }
 
+private module AwaitSatisfiesConstraint =
+  SatisfiesConstraint<AwaitTarget, AwaitSatisfiesConstraintInput>;
+
 pragma[nomagic]
 private Type inferAwaitExprType(AstNode n, TypePath path) {
   exists(TypePath exprPath |
-    SatisfiesConstraint<AwaitTarget, AwaitSatisfiesConstraintInput>::satisfiesConstraintType(n.(AwaitExpr)
-          .getExpr(), _, exprPath, result) and
+    AwaitSatisfiesConstraint::satisfiesConstraintType(n.(AwaitExpr).getExpr(), _, exprPath, result) and
     exprPath.isCons(getFutureOutputTypeParameter(), path)
   )
 }
@@ -3922,13 +3945,15 @@ private AssociatedTypeTypeParameter getIntoIteratorItemTypeParameter() {
   result = getAssociatedTypeTypeParameter(any(IntoIteratorTrait t).getItemType())
 }
 
+private module ForIterableSatisfiesConstraint =
+  SatisfiesConstraint<ForIterableExpr, ForIterableSatisfiesConstraintInput>;
+
 pragma[nomagic]
 private Type inferForLoopExprType(AstNode n, TypePath path) {
   // type of iterable -> type of pattern (loop variable)
   exists(ForExpr fe, TypePath exprPath, AssociatedTypeTypeParameter tp |
     n = fe.getPat() and
-    SatisfiesConstraint<ForIterableExpr, ForIterableSatisfiesConstraintInput>::satisfiesConstraintType(fe.getIterable(),
-      _, exprPath, result) and
+    ForIterableSatisfiesConstraint::satisfiesConstraintType(fe.getIterable(), _, exprPath, result) and
     exprPath.isCons(tp, path)
   |
     tp = getIntoIteratorItemTypeParameter()
@@ -3963,10 +3988,12 @@ private module InvokedClosureSatisfiesConstraintInput implements
   }
 }
 
+private module InvokedClosureSatisfiesConstraint =
+  SatisfiesConstraint<InvokedClosureExpr, InvokedClosureSatisfiesConstraintInput>;
+
 /** Gets the type of `ce` when viewed as an implementation of `FnOnce`. */
 private Type invokedClosureFnTypeAt(InvokedClosureExpr ce, TypePath path) {
-  SatisfiesConstraint<InvokedClosureExpr, InvokedClosureSatisfiesConstraintInput>::satisfiesConstraintType(ce,
-    _, path, result)
+  InvokedClosureSatisfiesConstraint::satisfiesConstraintType(ce, _, path, result)
 }
 
 /**

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

@@ -2740,6 +2740,7 @@ mod blanket_impl;
 mod closure;
 mod dereference;
 mod dyn_type;
+mod regressions;
 
 fn main() {
     field_access::f(); // $ target=f

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

@@ -0,0 +1,34 @@
+mod regression1 {
+
+    pub struct S<T>(T);
+
+    pub enum E {
+        V { vec: Vec<E> },
+    }
+
+    impl<T> From<S<T>> for Option<T> {
+        fn from(s: S<T>) -> Self {
+            Some(s.0) // $ fieldof=S
+        }
+    }
+
+    pub fn f() -> E {
+        let mut vec_e = Vec::new(); // $ target=new
+        let mut opt_e = None;
+
+        let e = E::V { vec: Vec::new() }; // $ target=new
+
+        if let Some(e) = opt_e {
+            vec_e.push(e); // $ target=push
+        }
+        opt_e = e.into(); // $ target=into
+
+        #[rustfmt::skip]
+        let _ = if let Some(last) = vec_e.pop() // $ target=pop
+        {
+            opt_e = last.into(); // $ target=into
+        };
+
+        opt_e.unwrap() // $ target=unwrap
+    }
+}