Revert getACallee type change

ql/lib/semmle/go/Scopes.qll

@@ -371,7 +371,7 @@ class Function extends ValueEntity, @functionobject {
   DataFlow::CallNode getACall() {
     this = result.getTarget()
     or
-    this.(DeclaredFunction).getFuncDecl() = result.getACallee()
+    this = result.getACalleeIncludingExternals().asFunction()
   }
 
   /** Gets the declaration of this function, if any. */

ql/lib/semmle/go/dataflow/internal/DataFlowDispatch.qll

@@ -93,7 +93,7 @@ DataFlowCallable viableCallable(CallExpr ma) {
     else
       if isInterfaceMethodCall(call)
       then result = getRestrictedInterfaceTarget(call)
-      else result.getFuncDef() = call.getACallee()
+      else result = call.getACalleeIncludingExternals()
   )
 }
 

ql/lib/semmle/go/dataflow/internal/DataFlowNodes.qll

@@ -449,20 +449,26 @@ module Public {
      * For virtual calls, we look up possible targets in all types that implement the receiver
      * interface type.
      */
-    FuncDef getACallee() {
-      result = this.getTarget().(DeclaredFunction).getFuncDecl()
+    DataFlowCallable getACalleeIncludingExternals() {
+      result.asFunction() = this.getTarget()
       or
       exists(DataFlow::Node calleeSource | calleeSource = this.getACalleeSource() |
-        result = calleeSource.asExpr()
+        result.asFuncLit() = calleeSource.asExpr()
         or
         exists(Method declared, Method actual |
           calleeSource = declared.getARead() and
           actual.implements(declared) and
-          result = actual.(DeclaredFunction).getFuncDecl()
+          result.asFunction() = actual
         )
       )
     }
 
+    /**
+     * As `getACalleeIncludingExternals`, except excluding external functions (those for which
+     * we lack a definition, such as standard library functions).
+     */
+    FuncDef getACallee() { result = this.getACalleeIncludingExternals().getFuncDef() }
+
     /** Gets the name of the function or method being called, if it can be determined. */
     string getCalleeName() { result = expr.getTarget().getName() or result = expr.getCalleeName() }
 

ql/lib/semmle/go/security/UnsafeUnzipSymlinkCustomizations.qll

@@ -86,7 +86,7 @@ module UnsafeUnzipSymlink {
    * Gets a `CallNode` that may call `node`'s enclosing function.
    */
   private DataFlow::CallNode getACaller(DataFlow::CallNode node) {
-    result.getACallee().getFuncDef() = node.getRoot()
+    result.getACallee() = node.getRoot()
   }
 
   /**

ql/src/InconsistentCode/MissingErrorCheck.ql

@@ -26,9 +26,9 @@ predicate isNil(DataFlow::Node node) { node = Builtin::nil().getARead() }
  * `nil` for the pointer return value at some return site.
  */
 predicate calleeMayReturnNilWithError(DataFlow::CallNode call) {
-  not exists(call.getACallee().getFuncDef())
+  not exists(call.getACallee())
   or
-  exists(FuncDef callee | callee = call.getACallee().getFuncDef() |
+  exists(FuncDef callee | callee = call.getACallee() |
     not exists(callee.getBody())
     or
     exists(IR::ReturnInstruction ret, DataFlow::Node ptrReturn, DataFlow::Node errReturn |

ql/src/Security/CWE-322/InsecureHostKeyCallback.ql

@@ -31,7 +31,7 @@ class HostKeyCallbackFunc extends DataFlow::Node {
     (
       this instanceof DataFlow::FunctionNode
       or
-      exists(DataFlow::CallNode call | not exists(call.getACallee().getFuncDef().getBody()) |
+      exists(DataFlow::CallNode call | not exists(call.getACallee().getBody()) |
         this = call.getAResult()
       )
     )

ql/src/Security/CWE-601/BadRedirectCheck.ql

@@ -54,9 +54,7 @@ predicate isCleaned(DataFlow::Node nd) {
   isCleaned(nd.getAPredecessor())
   or
   exists(FuncDef f, FunctionInput inp | nd = inp.getExitNode(f) |
-    forex(DataFlow::CallNode call | call.getACallee().getFuncDef() = f |
-      isCleaned(inp.getEntryNode(call))
-    )
+    forex(DataFlow::CallNode call | call.getACallee() = f | isCleaned(inp.getEntryNode(call)))
   )
 }
 
@@ -89,9 +87,7 @@ predicate urlPath(DataFlow::Node nd) {
   urlPath(nd.getAPredecessor())
   or
   exists(FuncDef f, FunctionInput inp | nd = inp.getExitNode(f) |
-    forex(DataFlow::CallNode call | call.getACallee().getFuncDef() = f |
-      urlPath(inp.getEntryNode(call))
-    )
+    forex(DataFlow::CallNode call | call.getACallee() = f | urlPath(inp.getEntryNode(call)))
   )
 }
 

ql/test/library-tests/semmle/go/dataflow/CallGraph/getACall.ql

@@ -1,11 +1,11 @@
 import go
 
 query predicate missingCall(DeclaredFunction f, DataFlow::CallNode call) {
-  call.getACallee().asFunction() = f and
+  call.getACallee() = f.getFuncDecl() and
   not call = f.getACall()
 }
 
 query predicate spuriousCall(DeclaredFunction f, DataFlow::CallNode call) {
   call = f.getACall() and
-  not call.getACallee().asFunction() = f
+  exists(FuncDecl fd | fd = f.getFuncDecl() | not call.getACallee() = fd)
 }

ql/test/library-tests/semmle/go/dataflow/CallGraph/getACallee.ql

@@ -16,10 +16,10 @@ string metadata(Locatable l, string key) {
 
 query predicate missingCallee(DataFlow::CallNode call, FuncDef callee) {
   metadata(call.asExpr(), "callee") = metadata(callee, "name") and
-  not call.getACallee().getFuncDef() = callee
+  not call.getACallee() = callee
 }
 
 query predicate spuriousCallee(DataFlow::CallNode call, FuncDef callee) {
-  call.getACallee().getFuncDef() = callee and
+  call.getACallee() = callee and
   not metadata(call.asExpr(), "callee") = metadata(callee, "name")
 }

ql/test/library-tests/semmle/go/dataflow/ExternalFlowVarArgs/Flows.ql

@@ -12,7 +12,7 @@ class SummaryModelTest extends SummaryModelCsv {
         "github.com/nonexistent/test;;false;FunctionWithSliceParameter;;;ArrayElement of Argument[0];ReturnValue;value",
         "github.com/nonexistent/test;;false;FunctionWithVarArgsParameter;;;ArrayElement of Argument[0];ReturnValue;value",
         "github.com/nonexistent/test;;false;FunctionWithSliceOfStructsParameter;;;Field[github.com/nonexistent/test.A.Field] of ArrayElement of Argument[0];ReturnValue;value",
-        "github.com/nonexistent/test;;false;FunctionWithVarArgsOfStructsParameter;;;Field[github.com/nonexistent/test.A.Field] of ArrayElement of Argument[0];ReturnValue;value",
+        "github.com/nonexistent/test;;false;FunctionWithVarArgsOfStructsParameter;;;Field[github.com/nonexistent/test.A.Field] of ArrayElement of Argument[0];ReturnValue;value"
       ]
   }
 }