Merge pull request #21355 from hvitved/rust/type-inference-unify

Rust: Unify call resolution logic

Author: hvitved

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

@@ -33,5 +33,11 @@ module Impl {
         result = "impl " + trait + this.getSelfTy().toAbbreviatedString() + " { ... }"
       )
     }
+
+    /**
+     * Holds if this is an inherent `impl` block, that is, one that does not implement a trait.
+     */
+    pragma[nomagic]
+    predicate isInherent() { not this.hasTrait() }
   }
 }

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

@@ -6,7 +6,10 @@ module Impl {
 
   private newtype TArgumentPosition =
     TPositionalArgumentPosition(int i) {
-      i in [0 .. max([any(ParamList l).getNumberOfParams(), any(ArgList l).getNumberOfArgs()]) - 1]
+      // For the type `FunctionPosition` used by type inference, we work with function-call syntax
+      // adjusted positions, so a call like `x.m(a, b, c)` needs positions `0` through `3`; for this
+      // reason, there is no `- 1` after `max(...)` below.
+      i in [0 .. max([any(ParamList l).getNumberOfParams(), any(ArgList l).getNumberOfArgs()])]
     } or
     TSelfArgumentPosition() or
     TTypeQualifierArgumentPosition()

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

@@ -41,16 +41,19 @@ private predicate hasFirstNonTrivialTraitBound(TypeParamItemNode tp, Trait trait
  */
 pragma[nomagic]
 predicate isBlanketLike(ImplItemNode i, TypePath blanketSelfPath, TypeParam blanketTypeParam) {
-  blanketTypeParam = i.getBlanketImplementationTypeParam() and
-  blanketSelfPath.isEmpty()
-  or
-  exists(TypeMention tm, Type root, TypeParameter tp |
-    tm = i.(Impl).getSelfTy() and
-    complexSelfRoot(root, tp) and
-    tm.getType() = root and
-    tm.getTypeAt(blanketSelfPath) = TTypeParamTypeParameter(blanketTypeParam) and
-    blanketSelfPath = TypePath::singleton(tp) and
-    hasFirstNonTrivialTraitBound(blanketTypeParam, _)
+  i.(Impl).hasTrait() and
+  (
+    blanketTypeParam = i.getBlanketImplementationTypeParam() and
+    blanketSelfPath.isEmpty()
+    or
+    exists(TypeMention tm, Type root, TypeParameter tp |
+      tm = i.(Impl).getSelfTy() and
+      complexSelfRoot(root, tp) and
+      tm.getType() = root and
+      tm.getTypeAt(blanketSelfPath) = TTypeParamTypeParameter(blanketTypeParam) and
+      blanketSelfPath = TypePath::singleton(tp) and
+      hasFirstNonTrivialTraitBound(blanketTypeParam, _)
+    )
   )
 }
 

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

@@ -124,7 +124,8 @@ private predicate functionResolutionDependsOnArgumentCand(
     implHasSibling(impl, trait) and
     traitTypeParameterOccurrence(trait, _, functionName, pos, path, traitTp) and
     f = impl.getASuccessor(functionName) and
-    not pos.isSelfOrTypeQualifier()
+    not pos.isTypeQualifier() and
+    not (f instanceof Method and pos.asPosition() = 0)
   )
 }
 

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

@@ -6,17 +6,23 @@ private import TypeMention
 private import TypeInference
 
 private newtype TFunctionPosition =
-  TArgumentFunctionPosition(ArgumentPosition pos) or
+  TArgumentFunctionPosition(ArgumentPosition pos) { not pos.isSelf() } or
   TReturnFunctionPosition()
 
 /**
- * A position of a type related to a function.
+ * A function-call adjusted position of a type related to a function.
  *
- * Either `self`, `return`, or a positional parameter index.
+ * Either `return` or a positional parameter index, where `self` is translated
+ * to position `0` and subsequent positional parameters at index `i` are
+ * translated to position `i + 1`.
+ *
+ * Function-call adjusted positions are needed when resolving calls of the
+ * form `Foo::f(x_1, ..., x_n)`, where we do not know up front whether `f` is a
+ * method or a non-method, and hence we need to be able to match `x_1` against
+ * both a potential `self` parameter and a potential first positional parameter
+ * (and `x_2, ... x_n` against all subsequent positional parameters).
  */
 class FunctionPosition extends TFunctionPosition {
-  predicate isSelf() { this.asArgumentPosition().isSelf() }
-
   int asPosition() { result = this.asArgumentPosition().asPosition() }
 
   predicate isPosition() { exists(this.asPosition()) }
@@ -25,29 +31,18 @@ class FunctionPosition extends TFunctionPosition {
 
   predicate isTypeQualifier() { this.asArgumentPosition().isTypeQualifier() }
 
-  predicate isSelfOrTypeQualifier() { this.isSelf() or this.isTypeQualifier() }
-
   predicate isReturn() { this = TReturnFunctionPosition() }
 
-  /** Gets the corresponding position when `f` is invoked via a function call. */
-  bindingset[f]
-  FunctionPosition getFunctionCallAdjusted(Function f) {
-    this.isReturn() and
-    result = this
-    or
-    if f.hasSelfParam()
-    then
-      this.isSelf() and result.asPosition() = 0
-      or
-      result.asPosition() = this.asPosition() + 1
-    else result = this
-  }
-
   TypeMention getTypeMention(Function f) {
-    this.isSelf() and
-    result = getSelfParamTypeMention(f.getSelfParam())
-    or
-    result = f.getParam(this.asPosition()).getTypeRepr()
+    (
+      if f instanceof Method
+      then
+        result = f.getParam(this.asPosition() - 1).getTypeRepr()
+        or
+        result = getSelfParamTypeMention(f.getSelfParam()) and
+        this.asPosition() = 0
+      else result = f.getParam(this.asPosition()).getTypeRepr()
+    )
     or
     this.isReturn() and
     result = getReturnTypeMention(f)
@@ -197,8 +192,7 @@ class AssocFunctionType extends MkAssocFunctionType {
     exists(Function f, ImplOrTraitItemNode i, FunctionPosition pos | this.appliesTo(f, i, pos) |
       result = pos.getTypeMention(f)
       or
-      pos.isSelf() and
-      not f.hasSelfParam() and
+      pos.isTypeQualifier() and
       result = [i.(Impl).getSelfTy().(AstNode), i.(Trait).getName()]
     )
   }
@@ -209,7 +203,7 @@ class AssocFunctionType extends MkAssocFunctionType {
 }
 
 pragma[nomagic]
-private Trait getALookupTrait(Type t) {
+Trait getALookupTrait(Type t) {
   result = t.(TypeParamTypeParameter).getTypeParam().(TypeParamItemNode).resolveABound()
   or
   result = t.(SelfTypeParameter).getTrait()
@@ -310,10 +304,11 @@ signature module ArgsAreInstantiationsOfInputSig {
    * Holds if `f` inside `i` needs to have the type corresponding to type parameter
    * `tp` checked.
    *
-   * If `i` is an inherent implementation, `tp` is a type parameter of the type being
-   * implemented, otherwise `tp` is a type parameter of the trait (being implemented).
+   * `tp` is a type parameter of the trait being implemented by `f` or the trait to which
+   * `f` belongs.
    *
-   * `pos` is one of the positions in `f` in which the relevant type occours.
+   * `pos` is one of the function-call adjusted positions in `f` in which the relevant
+   * type occurs.
    */
   predicate toCheck(ImplOrTraitItemNode i, Function f, TypeParameter tp, FunctionPosition pos);
 
@@ -360,7 +355,7 @@ module ArgsAreInstantiationsOf<ArgsAreInstantiationsOfInputSig Input> {
   private newtype TCallAndPos =
     MkCallAndPos(Input::Call call, FunctionPosition pos) { exists(call.getArgType(pos, _)) }
 
-  /** A call tagged with a position. */
+  /** A call tagged with a function-call adjusted position. */
   private class CallAndPos extends MkCallAndPos {
     Input::Call call;
     FunctionPosition pos;
@@ -413,20 +408,21 @@ module ArgsAreInstantiationsOf<ArgsAreInstantiationsOfInputSig Input> {
 
   pragma[nomagic]
   private predicate argIsInstantiationOf(
-    Input::Call call, FunctionPosition pos, ImplOrTraitItemNode i, Function f, int rnk
+    Input::Call call, ImplOrTraitItemNode i, Function f, int rnk
   ) {
-    ArgIsInstantiationOfToIndex::argIsInstantiationOf(MkCallAndPos(call, pos), i, _) and
-    toCheckRanked(i, f, _, pos, rnk)
+    exists(FunctionPosition pos |
+      ArgIsInstantiationOfToIndex::argIsInstantiationOf(MkCallAndPos(call, pos), i, _) and
+      toCheckRanked(i, f, _, pos, rnk)
+    )
   }
 
   pragma[nomagic]
   private predicate argsAreInstantiationsOfToIndex(
     Input::Call call, ImplOrTraitItemNode i, Function f, int rnk
   ) {
-    exists(FunctionPosition pos |
-      argIsInstantiationOf(call, pos, i, f, rnk) and
-      call.hasTargetCand(i, f)
-    |
+    argIsInstantiationOf(call, i, f, rnk) and
+    call.hasTargetCand(i, f) and
+    (
       rnk = 0
       or
       argsAreInstantiationsOfToIndex(call, i, f, rnk - 1)