From fbb25decf062349b0f28b3027d6be34a11f2a812 Mon Sep 17 00:00:00 2001
From: Bruce Hill <bruce@bruce-hill.com>
Date: Tue, 23 Apr 2024 12:50:30 -0400
Subject: Support struct literals as constants

---
 ast.c       | 24 ------------------------
 ast.h       |  1 -
 compile.c   |  4 ++--
 typecheck.c | 36 ++++++++++++++++++++++++++++++++++++
 typecheck.h |  1 +
 5 files changed, 39 insertions(+), 27 deletions(-)

diff --git a/ast.c b/ast.c
index 64464dc9..80681e10 100644
--- a/ast.c
+++ b/ast.c
@@ -196,28 +196,4 @@ bool is_idempotent(ast_t *ast)
     }
 }
 
-bool is_constant(ast_t *ast)
-{
-    switch (ast->tag) {
-    case Bool: case Int: case Num: case Nil: case TextLiteral: return true;
-    case TextJoin: {
-        auto text = Match(ast, TextJoin);
-        return !text->children || !text->children->next;
-    }
-    case Not: return is_constant(Match(ast, Not)->value);
-    case Negative: return is_constant(Match(ast, Negative)->value);
-    case BinaryOp: {
-        auto binop = Match(ast, BinaryOp);
-        switch (binop->op) {
-        case BINOP_UNKNOWN: case BINOP_POWER: case BINOP_CONCAT: case BINOP_MIN: case BINOP_MAX: case BINOP_CMP:
-            return false;
-        default:
-            return is_constant(binop->lhs) && is_constant(binop->rhs);
-        }
-    }
-    case Use: return true;
-    default: return false;
-    }
-}
-
 // vim: ts=4 sw=0 et cino=L2,l1,(0,W4,m1,\:0
diff --git a/ast.h b/ast.h
index 34c3ffa4..17ab7274 100644
--- a/ast.h
+++ b/ast.h
@@ -279,6 +279,5 @@ CORD type_ast_to_xml(type_ast_t *ast);
 int printf_ast(FILE *stream, const struct printf_info *info, const void *const args[]);
 ast_list_t *get_ast_children(ast_t *ast);
 bool is_idempotent(ast_t *ast);
-bool is_constant(ast_t *ast);
 
 // vim: ts=4 sw=0 et cino=L2,l1,(0,W4,m1,\:0
diff --git a/compile.c b/compile.c
index f8f2dfe2..09507212 100644
--- a/compile.c
+++ b/compile.c
@@ -1867,7 +1867,7 @@ void compile_namespace(env_t *env, const char *ns_name, ast_t *block)
             auto decl = Match(ast, Declare);
             type_t *t = get_type(ns_env, decl->value);
 
-            if (!is_constant(decl->value))
+            if (!is_constant(env, decl->value))
                 code_err(decl->value, "This value is supposed to be a compile-time constant, but I can't figure out how to make it one");
             CORD var_decl = CORD_all(compile_type(env, t), " ", compile(ns_env, decl->var), " = ", compile(ns_env, decl->value), ";\n");
             env->code->staticdefs = CORD_cat(env->code->staticdefs, var_decl);
@@ -2117,7 +2117,7 @@ module_code_t compile_file(ast_t *ast)
             type_t *t = get_type(env, decl->value);
             if (t->tag == AbortType || t->tag == VoidType)
                 code_err(stmt->ast, "You can't declare a variable with a %T value", t);
-            if (!is_constant(decl->value))
+            if (!is_constant(env, decl->value))
                 code_err(decl->value, "This value is not a valid constant initializer.");
 
             if (is_private) {
diff --git a/typecheck.c b/typecheck.c
index 72551d97..38071c21 100644
--- a/typecheck.c
+++ b/typecheck.c
@@ -953,4 +953,40 @@ type_t *parse_type_string(env_t *env, const char *str)
     return ast ? parse_type_ast(env, ast) : NULL;
 }
 
+bool is_constant(env_t *env, ast_t *ast)
+{
+    switch (ast->tag) {
+    case Bool: case Int: case Num: case Nil: case TextLiteral: return true;
+    case TextJoin: {
+        auto text = Match(ast, TextJoin);
+        return !text->children || !text->children->next;
+    }
+    case Not: return is_constant(env, Match(ast, Not)->value);
+    case Negative: return is_constant(env, Match(ast, Negative)->value);
+    case BinaryOp: {
+        auto binop = Match(ast, BinaryOp);
+        switch (binop->op) {
+        case BINOP_UNKNOWN: case BINOP_POWER: case BINOP_CONCAT: case BINOP_MIN: case BINOP_MAX: case BINOP_CMP:
+            return false;
+        default:
+            return is_constant(env, binop->lhs) && is_constant(env, binop->rhs);
+        }
+    }
+    case Use: return true;
+    case FunctionCall: {
+        // Constructors are allowed:
+        auto call = Match(ast, FunctionCall);
+        if (call->fn->tag != Var) return false;
+        binding_t *b = get_binding(env, Match(call->fn, Var)->name);
+        if (b == NULL || b->type->tag != TypeInfoType) return false;
+        for (arg_ast_t *arg = call->args; arg; arg = arg->next) {
+            if (!is_constant(env, arg->value))
+                return false;
+        }
+        return true;
+    }
+    default: return false;
+    }
+}
+
 // vim: ts=4 sw=0 et cino=L2,l1,(0,W4,m1,\:0
diff --git a/typecheck.h b/typecheck.h
index 295ac605..fd9f1f73 100644
--- a/typecheck.h
+++ b/typecheck.h
@@ -23,5 +23,6 @@ type_t *get_arg_ast_type(env_t *env, arg_ast_t *arg);
 bool can_be_mutated(env_t *env, ast_t *ast);
 type_t *parse_type_string(env_t *env, const char *str);
 type_t *get_method_type(env_t *env, ast_t *self, const char *name);
+bool is_constant(env_t *env, ast_t *ast);
 
 // vim: ts=4 sw=0 et cino=L2,l1,(0,W4,m1,\:0
-- 
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