Add @safeinfer to allow var to be used locally.

releasenotes.md

@@ -18,6 +18,7 @@
 - Improve error message for missing `$endif`.
 - `foo[x][y] = b` now interpreted as `(*&foo[x])[y] = b` which allows overloads to do chained [] accesses.
 - Error if a stack allocated variable is too big (configurable with `--max-stack-object-size`).
+- Add `@safeinfer` to allow `var` to be used locally.
 
 ### Fixes
 - List.remove_at would incorrectly trigger ASAN.

src/compiler/compiler_internal.h

@@ -466,6 +466,7 @@ typedef struct VarDecl_
 	bool is_temp : 1;
 	bool copy_const : 1;
 	bool defaulted : 1;
+	bool safe_infer : 1;
 	union
 	{
 		Expr *init_expr;

src/compiler/enums.h

@@ -307,6 +307,7 @@ typedef enum
 	ATTRIBUTE_PUBLIC,
 	ATTRIBUTE_PURE,
 	ATTRIBUTE_REFLECT,
+	ATTRIBUTE_SAFEINFER,
 	ATTRIBUTE_SAFEMACRO,
 	ATTRIBUTE_SECTION,
 	ATTRIBUTE_STRUCTLIKE,

src/compiler/parse_global.c

@@ -857,7 +857,7 @@ Decl *parse_local_decl_after_type(ParseContext *c, TypeInfo *type)
 
 	bool is_cond;
 	if (!parse_attributes(c, &decl->attributes, NULL, NULL, &is_cond)) return poisoned_decl;
-	decl->is_cond = true;
+	decl->is_cond = is_cond;
 	if (tok_is(c, TOKEN_EQ))
 	{
 		if (!decl)
@@ -949,6 +949,8 @@ Decl *parse_var_decl(ParseContext *c)
 	// analyser. The runtime variables must have an initializer unlike the CT ones.
 	advance_and_verify(c, TOKEN_VAR);
 	Decl *decl;
+	bool is_cond;
+	SourceSpan span;
 	switch (c->tok)
 	{
 		case TOKEN_CONST_IDENT:
@@ -957,6 +959,8 @@ Decl *parse_var_decl(ParseContext *c)
 		case TOKEN_IDENT:
 			decl = decl_new_var_current(c, NULL, VARDECL_LOCAL);
 			advance(c);
+			if (!parse_attributes(c, &decl->attributes, NULL, NULL, &is_cond)) return poisoned_decl;
+			decl->is_cond = is_cond;
 			if (!tok_is(c, TOKEN_EQ))
 			{
 				PRINT_ERROR_HERE("'var' must always have an initial value, or the type cannot be inferred.");
@@ -966,16 +970,16 @@ Decl *parse_var_decl(ParseContext *c)
 			ASSIGN_EXPR_OR_RET(decl->var.init_expr, parse_expr(c), poisoned_decl);
 			break;
 		case TOKEN_CT_IDENT:
-			decl = decl_new_var_current(c, NULL, VARDECL_LOCAL_CT);
-			advance(c);
-			if (try_consume(c, TOKEN_EQ))
-			{
-				ASSIGN_EXPR_OR_RET(decl->var.init_expr, parse_expr(c), poisoned_decl);
-			}
-			break;
 		case TOKEN_CT_TYPE_IDENT:
-			decl = decl_new_var_current(c, NULL, VARDECL_LOCAL_CT_TYPE);
+			decl = decl_new_var_current(c, NULL, c->tok == TOKEN_CT_IDENT ? VARDECL_LOCAL_CT : VARDECL_LOCAL_CT_TYPE);
 			advance(c);
+			span = c->span;
+			if (!parse_attributes(c, &decl->attributes, NULL, NULL, &is_cond)) return poisoned_decl;
+			if (is_cond || decl->attributes)
+			{
+				print_error_at(span, "Attributes are not allowed on compile time variables.");
+				return poisoned_decl;
+			}
 			if (try_consume(c, TOKEN_EQ))
 			{
 				ASSIGN_EXPR_OR_RET(decl->var.init_expr, parse_expr(c), poisoned_decl);

src/compiler/sema_decls.c

@@ -3055,6 +3055,7 @@ static bool sema_analyse_attribute(SemaContext *context, ResolvedAttrData *attr_
 			[ATTRIBUTE_PURE] = ATTR_CALL,
 			[ATTRIBUTE_REFLECT] = ATTR_FUNC | ATTR_GLOBAL | ATTR_CONST | USER_DEFINED_TYPES,
 			[ATTRIBUTE_SAFEMACRO] = ATTR_MACRO,
+			[ATTRIBUTE_SAFEINFER] = ATTR_GLOBAL | ATTR_LOCAL,
 			[ATTRIBUTE_SECTION] = ATTR_FUNC | ATTR_CONST | ATTR_GLOBAL,
 			[ATTRIBUTE_STRUCTLIKE] = ATTR_DISTINCT,
 			[ATTRIBUTE_TAG] = ATTR_BITSTRUCT_MEMBER | ATTR_MEMBER | USER_DEFINED_TYPES | CALLABLE_TYPE,
@@ -3421,6 +3422,9 @@ static bool sema_analyse_attribute(SemaContext *context, ResolvedAttrData *attr_
 			decl->attr_nopadding = true;
 			decl->attr_compact = true;
 			break;
+		case ATTRIBUTE_SAFEINFER:
+			decl->var.safe_infer = true;
+			break;
 		case ATTRIBUTE_NOINIT:
 			decl->var.no_init = true;
 			break;
@@ -4651,9 +4655,9 @@ bool sema_analyse_var_decl(SemaContext *context, Decl *decl, bool local)
 			return decl_poison(decl);
 		}
 		ASSERT(!decl->var.no_init);
-		if (kind == VARDECL_LOCAL && !context_is_macro(context) && init_expr->expr_kind != EXPR_LAMBDA)
+		if (kind == VARDECL_LOCAL && !context_is_macro(context) && init_expr->expr_kind != EXPR_LAMBDA && !decl->var.safe_infer)
 		{
-			SEMA_ERROR(decl, "Defining a variable using 'var %s = ...' is only allowed inside a macro, or when defining a lambda.", decl->name);
+			SEMA_ERROR(decl, "Defining a variable using 'var %s = ...' is only allowed inside a macro, or when defining a lambda. You can override this by adding the attribute '@safeinfer' to the declaration.", decl->name);
 			return decl_poison(decl);
 		}
 		if (!sema_analyse_expr(context, init_expr)) return decl_poison(decl);

src/compiler/symtab.c

@@ -372,6 +372,7 @@ void symtab_init(uint32_t capacity)
 	attribute_list[ATTRIBUTE_PURE] = kw_at_pure;
 	attribute_list[ATTRIBUTE_PUBLIC] = KW_DEF("@public");
 	attribute_list[ATTRIBUTE_REFLECT] = KW_DEF("@reflect");
+	attribute_list[ATTRIBUTE_SAFEINFER] = KW_DEF("@safeinfer");
 	attribute_list[ATTRIBUTE_SAFEMACRO] = KW_DEF("@safemacro");
 	attribute_list[ATTRIBUTE_SECTION] = KW_DEF("@section");
 	attribute_list[ATTRIBUTE_STRUCTLIKE] = KW_DEF("@structlike");

test/test_suite/attributes/safe_infer.c3

@@ -0,0 +1,5 @@
+fn int main(String[] args)
+{
+	var y @safeinfer = 1;
+    return 0;
+}

test/test_suite/statements/big_locals.c3

@@ -1,6 +1,6 @@
 import std;
 fn int main(String[] args)
 {
-	int[1024 * 1024] x; // #error: The size of this local variable (4096 Kb) exceeds the maximum allowed stack object size (128 Kb)
+	int[1024 * 1024] x; // #error: The size of this local variable (4096 Kb) exceeds the maximum allowed
     return 0;
 }