[clang] [clang][dataflow] Fully support Environment construction for Stmt analysis. (PR #91616)

[via cfe-commits]

================
@@ -641,23 +656,20 @@ class Environment {
   /// (or the flow condition is overly constraining) or if the solver times out.
   bool allows(const Formula &) const;
 
-  /// Returns the `DeclContext` of the block being analysed, if any. Otherwise,
-  /// returns null.
-  const DeclContext *getDeclCtx() const { return CallStack.back(); }
-
   /// Returns the function currently being analyzed, or null if the code being
   /// analyzed isn't part of a function.
   const FunctionDecl *getCurrentFunc() const {
-    return dyn_cast<FunctionDecl>(getDeclCtx());
+    return CallStack.empty() ? InitialTargetFunc : CallStack.back();
   }
 
   /// Returns the size of the call stack.
   size_t callStackSize() const { return CallStack.size(); }
 
   /// Returns whether this `Environment` can be extended to analyze the given
   /// `Callee` (i.e. if `pushCall` can be used), with recursion disallowed and a
-  /// given `MaxDepth`.
-  bool canDescend(unsigned MaxDepth, const DeclContext *Callee) const;
+  /// given `MaxDepth`. Note that the `MaxDepth` does not count any initial
+  /// target function, which was not called.
+  bool canDescend(unsigned MaxDepth, const FunctionDecl *Callee) const;
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martinboehme wrote:

Suggestion (can't make this a suggested edit as I'm suggesting to change a line that this PR doesn't touch):

```cxx
  /// Returns whether this `Environment` can be extended to analyze the given
  /// `Callee` (i.e. if `pushCall` can be used).
  /// Recursion is not allowed. `MaxDepth` is the maximum size of the call stack
  /// (i.e. the maximum value that `callStackSize()` may assume after the call).
```

https://github.com/llvm/llvm-project/pull/91616