Parameterized impl declarations (#1189)

* parameterized impls, first step

* bug fixes, comments, etc.

* added another test case, fix a bug in impl lookup

* simplify tests, removing tuple stuff

* don't create impl bindings for -bound implicit parameters

* remove a redundant 'private'

* CamelCase

* add missing backtick

* add a comment

executable_semantics/syntax/lexer.lpp

@@ -60,6 +60,7 @@ EXTERNAL             "external"
 FALSE                "false"
 FN                   "fn"
 FN_TYPE              "__Fn"
+FORALL               "forall"
 IF                   "if"
 IMPL                 "impl"
 IMPORT               "import"
@@ -162,6 +163,7 @@ string_literal        \"([^\\\"\n\v\f\r]|\\.)*\"
 {FALSE}               { return SIMPLE_TOKEN(FALSE);               }
 {FN_TYPE}             { return SIMPLE_TOKEN(FN_TYPE);             }
 {FN}                  { return SIMPLE_TOKEN(FN);                  }
+{FORALL}              { return SIMPLE_TOKEN(FORALL);              }
 {IF}                  { return SIMPLE_TOKEN(IF);                  }
 {IMPL}                { return SIMPLE_TOKEN(IMPL);                }
 {IMPORT}              { return SIMPLE_TOKEN(IMPORT);              }

executable_semantics/syntax/parser.ypp

@@ -141,6 +141,7 @@
 %type <Nonnull<Expression*>> expression
 %type <Nonnull<GenericBinding*>> generic_binding
 %type <std::vector<Nonnull<AstNode*>>> deduced_params
+%type <std::vector<Nonnull<AstNode*>>> impl_deduced_params
 %type <std::vector<Nonnull<AstNode*>>> deduced_param_list
 %type <Nonnull<Pattern*>> pattern
 %type <Nonnull<Pattern*>> non_expression_pattern
@@ -198,6 +199,7 @@
   FALSE
   FN
   FN_TYPE
+  FORALL
   IF
   IMPL
   IMPORT
@@ -810,6 +812,12 @@ deduced_params:
 | LEFT_SQUARE_BRACKET deduced_param_list RIGHT_SQUARE_BRACKET
     { $$ = $2; }
 ;
+impl_deduced_params:
+  // Empty
+    { $$ = std::vector<Nonnull<AstNode*>>(); }
+| FORALL LEFT_SQUARE_BRACKET deduced_param_list RIGHT_SQUARE_BRACKET
+    { $$ = $3; }
+;
 receiver:
   // Empty
     { $$ = std::nullopt; }
@@ -908,8 +916,17 @@ declaration:
           arena -> New<GenericBinding>(context.source_loc(), "Self", ty_ty);
       $$ = arena->New<InterfaceDeclaration>(context.source_loc(), $2, self, $4);
     }
-| impl_kind IMPL expression AS expression LEFT_CURLY_BRACE declaration_list RIGHT_CURLY_BRACE
-    { $$ = arena->New<ImplDeclaration>(context.source_loc(), $1, $3, $5, $7); }
+| impl_kind IMPL impl_deduced_params expression AS expression LEFT_CURLY_BRACE declaration_list RIGHT_CURLY_BRACE
+    {
+      ErrorOr<ImplDeclaration*> impl = ImplDeclaration::Create(
+          arena, context.source_loc(), $1, $4, $6, $3, $8);
+      if (impl.ok()) {
+        $$ = *impl;
+      } else {
+        context.RecordSyntaxError(impl.error().message());
+        YYERROR;
+      }
+    }
 ;
 impl_kind:
   // Internal