add compile error for using outer scoped runtime variables

from a fn defined inside it. closes #876

src/all_types.hpp

@@ -2350,6 +2350,7 @@ struct IrInstructionVarPtr {
     IrInstruction base;
 
     ZigVar *var;
+    ScopeFnDef *crossed_fndef_scope;
 };
 
 struct IrInstructionCall {

src/analyze.cpp

@@ -3519,7 +3519,7 @@ ZigVar *add_variable(CodeGen *g, AstNode *source_node, Scope *parent_scope, Buf
     if (!type_is_invalid(value->type)) {
         variable_entry->align_bytes = get_abi_alignment(g, value->type);
 
-        ZigVar *existing_var = find_variable(g, parent_scope, name);
+        ZigVar *existing_var = find_variable(g, parent_scope, name, nullptr);
         if (existing_var && !existing_var->shadowable) {
             ErrorMsg *msg = add_node_error(g, source_node,
                     buf_sprintf("redeclaration of variable '%s'", buf_ptr(name)));
@@ -3726,12 +3726,16 @@ Tld *find_decl(CodeGen *g, Scope *scope, Buf *name) {
     return nullptr;
 }
 
-ZigVar *find_variable(CodeGen *g, Scope *scope, Buf *name) {
+ZigVar *find_variable(CodeGen *g, Scope *scope, Buf *name, ScopeFnDef **crossed_fndef_scope) {
+    ScopeFnDef *my_crossed_fndef_scope = nullptr;
     while (scope) {
         if (scope->id == ScopeIdVarDecl) {
             ScopeVarDecl *var_scope = (ScopeVarDecl *)scope;
-            if (buf_eql_buf(name, &var_scope->var->name))
+            if (buf_eql_buf(name, &var_scope->var->name)) {
+                if (crossed_fndef_scope != nullptr)
+                    *crossed_fndef_scope = my_crossed_fndef_scope;
                 return var_scope->var;
+            }
         } else if (scope->id == ScopeIdDecls) {
             ScopeDecls *decls_scope = (ScopeDecls *)scope;
             auto entry = decls_scope->decl_table.maybe_get(name);
@@ -3739,10 +3743,15 @@ ZigVar *find_variable(CodeGen *g, Scope *scope, Buf *name) {
                 Tld *tld = entry->value;
                 if (tld->id == TldIdVar) {
                     TldVar *tld_var = (TldVar *)tld;
-                    if (tld_var->var)
+                    if (tld_var->var) {
+                        if (crossed_fndef_scope != nullptr)
+                            *crossed_fndef_scope = nullptr;
                         return tld_var->var;
+                    }
                 }
             }
+        } else if (scope->id == ScopeIdFnDef) {
+            my_crossed_fndef_scope = (ScopeFnDef *)scope;
         }
         scope = scope->parent;
     }

src/analyze.hpp

@@ -48,7 +48,7 @@ bool type_has_bits(ZigType *type_entry);
 ImportTableEntry *add_source_file(CodeGen *g, PackageTableEntry *package, Buf *abs_full_path, Buf *source_code);
 
 
-ZigVar *find_variable(CodeGen *g, Scope *orig_context, Buf *name);
+ZigVar *find_variable(CodeGen *g, Scope *orig_context, Buf *name, ScopeFnDef **crossed_fndef_scope);
 Tld *find_decl(CodeGen *g, Scope *scope, Buf *name);
 void resolve_top_level_decl(CodeGen *g, Tld *tld, bool pointer_only, AstNode *source_node);
 bool type_is_codegen_pointer(ZigType *type);

src/ir.cpp

@@ -1114,15 +1114,22 @@ static IrInstruction *ir_build_bin_op_from(IrBuilder *irb, IrInstruction *old_in
     return new_instruction;
 }
 
-static IrInstruction *ir_build_var_ptr(IrBuilder *irb, Scope *scope, AstNode *source_node, ZigVar *var) {
+static IrInstruction *ir_build_var_ptr_x(IrBuilder *irb, Scope *scope, AstNode *source_node, ZigVar *var,
+        ScopeFnDef *crossed_fndef_scope)
+{
     IrInstructionVarPtr *instruction = ir_build_instruction<IrInstructionVarPtr>(irb, scope, source_node);
     instruction->var = var;
+    instruction->crossed_fndef_scope = crossed_fndef_scope;
 
     ir_ref_var(var);
 
     return &instruction->base;
 }
 
+static IrInstruction *ir_build_var_ptr(IrBuilder *irb, Scope *scope, AstNode *source_node, ZigVar *var) {
+    return ir_build_var_ptr_x(irb, scope, source_node, var, nullptr);
+}
+
 static IrInstruction *ir_build_elem_ptr(IrBuilder *irb, Scope *scope, AstNode *source_node, IrInstruction *array_ptr,
         IrInstruction *elem_index, bool safety_check_on, PtrLen ptr_len)
 {
@@ -3336,7 +3343,7 @@ static ZigVar *create_local_var(CodeGen *codegen, AstNode *node, Scope *parent_s
         buf_init_from_buf(&variable_entry->name, name);
 
         if (!skip_name_check) {
-            ZigVar *existing_var = find_variable(codegen, parent_scope, name);
+            ZigVar *existing_var = find_variable(codegen, parent_scope, name, nullptr);
             if (existing_var && !existing_var->shadowable) {
                 ErrorMsg *msg = add_node_error(codegen, node,
                         buf_sprintf("redeclaration of variable '%s'", buf_ptr(name)));
@@ -3799,9 +3806,10 @@ static IrInstruction *ir_gen_symbol(IrBuilder *irb, Scope *scope, AstNode *node,
         }
     }
 
-    ZigVar *var = find_variable(irb->codegen, scope, variable_name);
+    ScopeFnDef *crossed_fndef_scope;
+    ZigVar *var = find_variable(irb->codegen, scope, variable_name, &crossed_fndef_scope);
     if (var) {
-        IrInstruction *var_ptr = ir_build_var_ptr(irb, scope, node, var);
+        IrInstruction *var_ptr = ir_build_var_ptr_x(irb, scope, node, var, crossed_fndef_scope);
         if (lval == LValPtr)
             return var_ptr;
         else
@@ -5822,7 +5830,9 @@ static IrInstruction *ir_gen_asm_expr(IrBuilder *irb, Scope *scope, AstNode *nod
             output_types[i] = return_type;
         } else {
             Buf *variable_name = asm_output->variable_name;
-            ZigVar *var = find_variable(irb->codegen, scope, variable_name);
+            // TODO there is some duplication here with ir_gen_symbol. I need to do a full audit of how
+            // inline assembly works. https://github.com/ziglang/zig/issues/215
+            ZigVar *var = find_variable(irb->codegen, scope, variable_name, nullptr);
             if (var) {
                 output_vars[i] = var;
             } else {
@@ -14157,17 +14167,26 @@ static ZigType *ir_analyze_instruction_phi(IrAnalyze *ira, IrInstructionPhi *phi
     return resolved_type;
 }
 
-static ZigType *ir_analyze_var_ptr(IrAnalyze *ira, IrInstruction *instruction,
+static ZigType *ir_analyze_var_ptr(IrAnalyze *ira, IrInstruction *instruction, ZigVar *var) {
-        ZigVar *var)
-{
     IrInstruction *result = ir_get_var_ptr(ira, instruction, var);
     ir_link_new_instruction(result, instruction);
     return result->value.type;
 }
 
-static ZigType *ir_analyze_instruction_var_ptr(IrAnalyze *ira, IrInstructionVarPtr *var_ptr_instruction) {
+static ZigType *ir_analyze_instruction_var_ptr(IrAnalyze *ira, IrInstructionVarPtr *instruction) {
-    ZigVar *var = var_ptr_instruction->var;
+    ZigVar *var = instruction->var;
-    return ir_analyze_var_ptr(ira, &var_ptr_instruction->base, var);
+    IrInstruction *result = ir_get_var_ptr(ira, &instruction->base, var);
+    if (instruction->crossed_fndef_scope != nullptr && !instr_is_comptime(result)) {
+        ErrorMsg *msg = ir_add_error(ira, &instruction->base,
+            buf_sprintf("'%s' not accessible from inner function", buf_ptr(&var->name)));
+        add_error_note(ira->codegen, msg, instruction->crossed_fndef_scope->base.source_node,
+                buf_sprintf("crossed function definition here"));
+        add_error_note(ira->codegen, msg, var->decl_node,
+                buf_sprintf("declared here"));
+        return ira->codegen->builtin_types.entry_invalid;
+    }
+    ir_link_new_instruction(result, &instruction->base);
+    return result->value.type;
 }
 
 static ZigType *adjust_ptr_align(CodeGen *g, ZigType *ptr_type, uint32_t new_align) {

test/cases/fn.zig

@@ -176,3 +176,18 @@ test "pass by non-copying value as method, at comptime" {
         assert(pt.addPointCoords() == 3);
     }
 }
+
+fn outer(y: u32) fn (u32) u32 {
+    const Y = @typeOf(y);
+    const st = struct {
+        fn get(z: u32) u32 {
+            return z + @sizeOf(Y);
+        }
+    };
+    return st.get;
+}
+
+test "return inner function which references comptime variable of outer function" {
+    var func = outer(10);
+    assert(func(3) == 7);
+}

test/compile_errors.zig

@@ -1,6 +1,26 @@
 const tests = @import("tests.zig");
 
 pub fn addCases(cases: *tests.CompileErrorContext) void {
+    cases.add(
+        "accessing runtime parameter from outer function",
+        \\fn outer(y: u32) fn (u32) u32 {
+        \\    const st = struct {
+        \\        fn get(z: u32) u32 {
+        \\            return z + y;
+        \\        }
+        \\    };
+        \\    return st.get;
+        \\}
+        \\export fn entry() void {
+        \\    var func = outer(10);
+        \\    var x = func(3);
+        \\}
+    ,
+        ".tmp_source.zig:4:24: error: 'y' not accessible from inner function",
+        ".tmp_source.zig:3:28: note: crossed function definition here",
+        ".tmp_source.zig:1:10: note: declared here",
+    );
+
     cases.add(
         "non int passed to @intToFloat",
         \\export fn entry() void {