Take exhaustive match into account when checking for field initialization

.release-notes/issue-3616.md

@@ -0,0 +1,23 @@
+## Take exhaustive match into account when checking for field initialization
+
+Previously, exhaustive matches were handled after we verified that an object's fields were initialized. This lead to the code such as the following not passing compiler checks:
+
+```pony
+primitive Foo
+  fun apply() : (U32 | None) => 1
+
+type Bar is (U32 | None)
+
+actor Main
+  let bar : Bar
+
+  new create(env : Env) =>
+      match Foo()
+      | let result : U32 =>
+          bar = result
+      | None =>
+          bar = 0
+      end
+```
+
+Field initialization is now done in a later pass after exhaustiveness checking has been done.

src/libponyc/CMakeLists.txt

@@ -53,6 +53,7 @@ add_library(libponyc STATIC
     expr/postfix.c
     expr/reference.c
     options/options.c
+    pass/completeness.c
     pass/docgen.c
     pass/expr.c
     pass/finalisers.c

src/libponyc/pass/completeness.c

@@ -0,0 +1,53 @@
+#include "completeness.h"
+#include "ponyassert.h"
+
+static bool completeness_match(pass_opt_t* opt, ast_t* ast)
+{
+  (void)opt;
+  pony_assert(ast_id(ast) == TK_MATCH);
+  AST_GET_CHILDREN(ast, expr, cases, else_clause);
+
+  size_t branch_count = 0;
+
+  if(!ast_checkflag(cases, AST_FLAG_JUMPS_AWAY))
+  {
+    branch_count++;
+    ast_inheritbranch(ast, cases);
+  }
+
+  // An else_clause of TK_NONE doesn't cont as a branch because, we are after
+  // exhaustive match checking is done so, an else clause of TK_NONE means that
+  // we don't need the else and have an exhaustive match.
+  if(ast_id(else_clause) != TK_NONE &&
+    !ast_checkflag(else_clause, AST_FLAG_JUMPS_AWAY))
+  {
+    branch_count++;
+    ast_inheritbranch(ast, else_clause);
+  }
+
+  // If all branches jump away with no value, then we do too.
+  if(branch_count == 0)
+    ast_setflag(ast, AST_FLAG_JUMPS_AWAY);
+
+  ast_consolidate_branches(ast, branch_count);
+
+  // Push our symbol status to our parent scope.
+  ast_inheritstatus(ast_parent(ast), ast);
+
+  return true;
+}
+
+ast_result_t pass_completeness(ast_t** astp, pass_opt_t* options)
+{
+  ast_t* ast = *astp;
+
+  switch(ast_id(ast))
+  {
+    case TK_MATCH:
+      completeness_match(options, ast); break;
+    default:
+      {}
+  }
+
+  return AST_OK;
+}

src/libponyc/pass/completeness.h

@@ -0,0 +1,14 @@
+#ifndef PASS_COMPLETENESS_H
+#define PASS_COMPLETENESS_H
+
+#include <platform.h>
+#include "../ast/ast.h"
+#include "../pass/pass.h"
+
+PONY_EXTERN_C_BEGIN
+
+ast_result_t pass_completeness(ast_t** astp, pass_opt_t* options);
+
+PONY_EXTERN_C_END
+
+#endif

src/libponyc/pass/pass.c

@@ -8,6 +8,7 @@
 #include "traits.h"
 #include "refer.h"
 #include "expr.h"
+#include "completeness.h"
 #include "verify.h"
 #include "finalisers.h"
 #include "serialisers.h"
@@ -60,6 +61,7 @@ const char* pass_name(pass_id pass)
     case PASS_DOCS: return "docs";
     case PASS_REFER: return "refer";
     case PASS_EXPR: return "expr";
+    case PASS_COMPLETENESS: return "completeness";
     case PASS_VERIFY: return "verify";
     case PASS_FINALISER: return "final";
     case PASS_SERIALISER: return "serialise";
@@ -272,6 +274,13 @@ static bool ast_passes(ast_t** astp, pass_opt_t* options, pass_id last)
   if(is_program)
     plugin_visit_ast(*astp, options, PASS_EXPR);
 
+  if(!visit_pass(astp, options, last, &r, PASS_COMPLETENESS, NULL,
+    pass_completeness))
+    return r;
+
+  if(is_program)
+    plugin_visit_ast(*astp, options, PASS_COMPLETENESS);
+
   if(!visit_pass(astp, options, last, &r, PASS_VERIFY, NULL, pass_verify))
     return r;
 

src/libponyc/pass/pass.h

@@ -153,6 +153,14 @@ Also performs some "sugar" replacements that require knowledge of types.
 Mutates the AST extensively.
 
 
+* Completeness pass (AST)
+
+Does fixup of the AST that needs to be done after the expression pass and before
+verification.
+
+Mutates the AST.
+
+
 * Verify pass (AST)
 
 Perform various checks that are not required for type resolution, and are not
@@ -218,6 +226,7 @@ typedef enum pass_id
   PASS_DOCS,
   PASS_REFER,
   PASS_EXPR,
+  PASS_COMPLETENESS,
   PASS_VERIFY,
   PASS_FINALISER,
   PASS_SERIALISER,
@@ -245,6 +254,7 @@ typedef enum pass_id
     "    =docs\n" \
     "    =refer\n" \
     "    =expr\n" \
+    "    =completeness\n" \
     "    =verify\n" \
     "    =final\n" \
     "    =serialise\n" \

src/libponyc/pass/refer.c

@@ -1258,49 +1258,6 @@ static bool refer_pre_new(pass_opt_t* opt, ast_t* ast)
   return true;
 }
 
-static bool refer_new(pass_opt_t* opt, ast_t* ast)
-{
-  pony_assert(ast_id(ast) == TK_NEW);
-
-  ast_t* members = ast_parent(ast);
-  ast_t* member = ast_child(members);
-  bool result = true;
-
-  while(member != NULL)
-  {
-    switch(ast_id(member))
-    {
-      case TK_FVAR:
-      case TK_FLET:
-      case TK_EMBED:
-      {
-        sym_status_t status;
-        ast_t* id = ast_child(member);
-        ast_t* def = ast_get(ast, ast_name(id), &status);
-
-        if((def != member) || (status != SYM_DEFINED))
-        {
-          ast_error(opt->check.errors, def,
-            "field left undefined in constructor");
-          result = false;
-        }
-
-        break;
-      }
-
-      default: {}
-    }
-
-    member = ast_sibling(member);
-  }
-
-  if(!result)
-    ast_error(opt->check.errors, ast,
-      "constructor with undefined fields is here");
-
-  return result;
-}
-
 static bool refer_local(pass_opt_t* opt, ast_t* ast)
 {
   pony_assert(ast != NULL);
@@ -1843,7 +1800,6 @@ ast_result_t pass_refer(ast_t** astp, pass_opt_t* options)
     case TK_CONSUME:   r = refer_consume(options, ast); break;
 
     case TK_THIS:      r = refer_this(options, ast); break;
-    case TK_NEW:       r = refer_new(options, ast); break;
     case TK_VAR:
     case TK_LET:       r = refer_local(options, ast); break;
 

src/libponyc/verify/fun.c

@@ -487,6 +487,51 @@ static bool show_partiality(pass_opt_t* opt, ast_t* ast)
   return false;
 }
 
+bool verify_fields_are_defined_in_constructor(pass_opt_t* opt, ast_t* ast)
+{
+  bool result = true;
+
+  if(ast_id(ast) != TK_NEW)
+    return result;
+
+  ast_t* members = ast_parent(ast);
+  ast_t* member = ast_child(members);
+
+  while(member != NULL)
+  {
+    switch(ast_id(member))
+    {
+      case TK_FVAR:
+      case TK_FLET:
+      case TK_EMBED:
+      {
+        sym_status_t status;
+        ast_t* id = ast_child(member);
+        ast_t* def = ast_get(ast, ast_name(id), &status);
+
+        if((def != member) || (status != SYM_DEFINED))
+        {
+          ast_error(opt->check.errors, def,
+            "field left undefined in constructor");
+          result = false;
+        }
+
+        break;
+      }
+
+      default: {}
+    }
+
+    member = ast_sibling(member);
+  }
+
+  if(!result)
+    ast_error(opt->check.errors, ast,
+      "constructor with undefined fields is here");
+
+  return result;
+}
+
 bool verify_fun(pass_opt_t* opt, ast_t* ast)
 {
   pony_assert((ast_id(ast) == TK_BE) || (ast_id(ast) == TK_FUN) ||
@@ -498,7 +543,8 @@ bool verify_fun(pass_opt_t* opt, ast_t* ast)
     !verify_main_runtime_override_defaults(opt, ast) ||
     !verify_primitive_init(opt, ast) ||
     !verify_any_final(opt, ast) ||
-    !verify_any_serialise(opt, ast))
+    !verify_any_serialise(opt, ast) ||
+    !verify_fields_are_defined_in_constructor(opt, ast))
     return false;
 
   // Check partial functions.

src/libponyc/verify/fun.h

@@ -8,6 +8,7 @@
 PONY_EXTERN_C_BEGIN
 
 bool verify_fun(pass_opt_t* opt, ast_t* ast);
+bool verify_fields_are_defined_in_constructor(pass_opt_t* opt, ast_t* ast);
 
 PONY_EXTERN_C_END
 

test/libponyc-run/regression-3615/main.pony

@@ -0,0 +1,15 @@
+primitive Foo
+  fun apply() : (U32 | None) => 1
+
+type Bar is (U32 | None)
+
+actor Main
+  let bar : Bar
+
+  new create(env : Env) =>
+      match Foo()
+      | let result : U32 =>
+          bar = result
+      | None =>
+          bar = 0
+      end