Use symbol table from definition scope when looking up references from default method bodies

.release-notes/4027.md

@@ -0,0 +1,7 @@
+## Use symbol table from definition scope when looking up references from default method bodies
+
+Previously, symbols from default method bodies were only looked up in the local scope of the file into which they were included. This resulted in compilation errors if said symbol wasn't available in the local scope.
+
+Issues [#3737](https://github.com/ponylang/ponyc/issues/3737) and [#2150](https://github.com/ponylang/ponyc/issues/2150) were both examples of this problem.
+
+We've updated definition lookup to check if the enclosing method is provided by a trait or interface and if it is, to also check to definition scope for any needed symbols.

src/libponyc/ast/ast.c

@@ -1892,6 +1892,33 @@ void ast_extract_children(ast_t* parent, size_t child_count,
   }
 }
 
+ast_t* ast_get_provided_symbol_definition(ast_t* ast,
+  const char* name, sym_status_t* status)
+{
+  // The definition isn't in the local scope. let's check to see if our
+  // parent has a provided method body from a trait or interface. If yes,
+  // then we will find our definition.
+  ast_t* def = NULL;
+  bool found = false;
+
+  while(ast != NULL && !found)
+  {
+    if((ast_id(ast) == TK_FUN) || (ast_id(ast) == TK_BE))
+    {
+      // Methods with defaults provided by a trait/interface store the ast
+      // of the provided body in the ast data.
+      ast_t* body_donor = (ast_t *)ast_data(ast);
+      if (body_donor != NULL)
+        def = ast_get(body_donor, name, status);
+      found = true;
+    }
+
+    ast = ast_parent(ast);
+  }
+
+  return def;
+}
+
 static void ast_signature_serialise_trace(pony_ctx_t* ctx, void* object)
 {
   ast_t* ast = (ast_t*)object;

src/libponyc/ast/ast.h

@@ -213,6 +213,9 @@ void ast_extract_children(ast_t* parent, size_t child_count,
       children); \
   }
 
+ast_t* ast_get_provided_symbol_definition(ast_t* ast,
+  const char* name, sym_status_t* status);
+
 pony_type_t* ast_signature_pony_type();
 
 pony_type_t* ast_nominal_pkg_id_signature_pony_type();

src/libponyc/pass/names.c

@@ -319,6 +319,9 @@ bool names_nominal(pass_opt_t* opt, ast_t* scope, ast_t** astp, bool expr)
   }
 
   ast_t* def = ast_get(r_scope, name, NULL);
+  if(def == NULL)
+    def = ast_get_provided_symbol_definition(ast, name, NULL);
+
   bool r = true;
 
   if(def == NULL)

src/libponyc/pass/refer.c

@@ -435,9 +435,10 @@ bool refer_reference(pass_opt_t* opt, ast_t** astp)
     return true;
   }
 
-  // Everything we reference must be in scope, so we can use ast_get for lookup.
   sym_status_t status;
-  ast_t* def = ast_get(ast, ast_name(ast_child(ast)), &status);
+  ast_t* def = ast_get(ast, name, &status);
+  if(def == NULL)
+    def = ast_get_provided_symbol_definition(ast, name, &status);
 
   // If nothing was found, we fail, but also try to suggest an alternate name.
   if(def == NULL)

test/libponyc-run/regression-2150/bar.pony

@@ -0,0 +1,8 @@
+class Bar[T: Stringable #read] is Foo[T]
+  let _t: T
+
+  new create(t: T) =>
+    _t = t
+
+  fun foo(): this->T =>
+    _t

test/libponyc-run/regression-2150/foo.pony

@@ -0,0 +1,7 @@
+use "debug"
+
+trait Foo[T: Stringable #read]
+  fun foo(): this->T
+
+  fun bar() =>
+    Debug.out(foo().string())

test/libponyc-run/regression-2150/main.pony

@@ -0,0 +1,4 @@
+actor Main
+  new create(env: Env) =>
+    let b = Bar[I32](123)
+    b.bar()

test/libponyc-run/regression-3737/lib/lib.pony

@@ -0,0 +1,4 @@
+primitive LibPrimitive
+
+trait LibTrait
+  fun foo(): LibPrimitive => LibPrimitive

test/libponyc-run/regression-3737/main.pony

@@ -0,0 +1,5 @@
+use l = "./lib"
+
+actor Main is l.LibTrait
+  new create(env: Env) =>
+    None