fix[lang]: fix certain varinfo comparisons (#4164)

for `VarInfo`s which are declared in memory, the `VarInfo`
initialization is missing `decl_node`, and therefore different
variables with the same type get detected as overlapping in loop
iterator modification detection. this commit properly initializes
memory `VarInfo`s with the appropriate `decl_node`.

---------

Co-authored-by: cyberthirst <[email protected]>

tests/functional/codegen/features/iteration/test_for_in_list.py

@@ -897,3 +897,36 @@ def foo():
         compile_code(main, input_bundle=input_bundle)
 
     assert e.value._message == "Cannot modify loop variable `queue`"
+
+
+def test_iterator_modification_memory(get_contract):
+    code = """
+@external
+def foo() -> DynArray[uint256, 10]:
+    # check VarInfos are distinguished by decl_node when they have same type
+    alreadyDone: DynArray[uint256, 10] = []
+    _assets: DynArray[uint256, 10] = [1, 2, 3, 4, 3, 2, 1]
+    for a: uint256 in _assets:
+        if a in alreadyDone:
+            continue
+        alreadyDone.append(a)
+    return alreadyDone
+    """
+    c = get_contract(code)
+    assert c.foo() == [1, 2, 3, 4]
+
+
+def test_iterator_modification_func_arg(get_contract):
+    code = """
+@internal
+def boo(a: DynArray[uint256, 12] = [], b: DynArray[uint256, 12] = []) -> DynArray[uint256, 12]:
+    for i: uint256 in a:
+        b.append(i)
+    return b
+
+@external
+def foo() -> DynArray[uint256, 12]:
+    return self.boo([1, 2, 3])
+    """
+    c = get_contract(code)
+    assert c.foo() == [1, 2, 3]

tests/unit/ast/test_ast_dict.py

@@ -1255,7 +1255,13 @@ def qux2():
         {
             "annotation": {"ast_type": "Name", "id": "uint256"},
             "ast_type": "AnnAssign",
-            "target": {"ast_type": "Name", "id": "x"},
+            "target": {
+                "ast_type": "Name",
+                "id": "x",
+                "variable_reads": [
+                    {"name": "x", "decl_node": {"node_id": 15, "source_id": 0}, "access_path": []}
+                ],
+            },
             "value": {
                 "ast_type": "Attribute",
                 "attr": "counter",
@@ -1300,7 +1306,13 @@ def qux2():
         {
             "annotation": {"ast_type": "Name", "id": "uint256"},
             "ast_type": "AnnAssign",
-            "target": {"ast_type": "Name", "id": "x"},
+            "target": {
+                "ast_type": "Name",
+                "id": "x",
+                "variable_reads": [
+                    {"name": "x", "decl_node": {"node_id": 35, "source_id": 0}, "access_path": []}
+                ],
+            },
             "value": {
                 "ast_type": "Attribute",
                 "attr": "counter",
@@ -1317,7 +1329,13 @@ def qux2():
         {
             "annotation": {"ast_type": "Name", "id": "uint256"},
             "ast_type": "AnnAssign",
-            "target": {"ast_type": "Name", "id": "y"},
+            "target": {
+                "ast_type": "Name",
+                "id": "y",
+                "variable_reads": [
+                    {"name": "y", "decl_node": {"node_id": 44, "source_id": 0}, "access_path": []}
+                ],
+            },
             "value": {
                 "ast_type": "Attribute",
                 "attr": "counter",

vyper/semantics/analysis/base.py

@@ -257,7 +257,10 @@ def to_dict(self):
         # map SUBSCRIPT_ACCESS to `"$subscript_access"` (which is an identifier
         # which can't be constructed by the user)
         path = ["$subscript_access" if s is self.SUBSCRIPT_ACCESS else s for s in self.path]
-        varname = var.decl_node.target.id
+        if isinstance(var.decl_node, vy_ast.arg):
+            varname = var.decl_node.arg
+        else:
+            varname = var.decl_node.target.id
 
         decl_node = var.decl_node.get_id_dict()
         ret = {"name": varname, "decl_node": decl_node, "access_path": path}

vyper/semantics/analysis/local.py

@@ -317,7 +317,7 @@ def analyze(self):
 
         for arg in self.func.arguments:
             self.namespace[arg.name] = VarInfo(
-                arg.typ, location=location, modifiability=modifiability
+                arg.typ, location=location, modifiability=modifiability, decl_node=arg.ast_source
             )
 
         for node in self.fn_node.body:
@@ -363,7 +363,7 @@ def visit_AnnAssign(self, node):
         # validate the value before adding it to the namespace
         self.expr_visitor.visit(node.value, typ)
 
-        self.namespace[name] = VarInfo(typ, location=DataLocation.MEMORY)
+        self.namespace[name] = VarInfo(typ, location=DataLocation.MEMORY, decl_node=node)
 
         self.expr_visitor.visit(node.target, typ)
 
@@ -575,7 +575,7 @@ def visit_For(self, node):
             target_name = node.target.target.id
             # maybe we should introduce a new Modifiability: LOOP_VARIABLE
             self.namespace[target_name] = VarInfo(
-                target_type, modifiability=Modifiability.RUNTIME_CONSTANT
+                target_type, modifiability=Modifiability.RUNTIME_CONSTANT, decl_node=node.target
             )
 
             self.expr_visitor.visit(node.target.target, target_type)