From 97c2437d975f225784e0d6c16a737403c5a2fb47 Mon Sep 17 00:00:00 2001
From: Luna <git@l4.pm>
Date: Thu, 26 Sep 2019 16:04:11 -0300
Subject: [PATCH] add basic business logic for scopes

---
 src/comp_ctx.zig | 67 +++++++++++++++++++++++++++++++++++++++---------
 src/types.zig    | 16 ++++++++++--
 2 files changed, 69 insertions(+), 14 deletions(-)

diff --git a/src/comp_ctx.zig b/src/comp_ctx.zig
index ddb8e89..0668e8a 100644
--- a/src/comp_ctx.zig
+++ b/src/comp_ctx.zig
@@ -29,10 +29,31 @@ pub const SymbolUnderlyingType = union(SymbolUnderlyingTypeEnum) {
     Enum: []const u8,
 };
 
-pub const Scope = std.StringHashMap(SymbolUnderlyingType);
-pub const Environment = struct {
-    parent: *Environment,
-    scope: Scope,
+pub const Environment = std.StringHashMap(SymbolUnderlyingType);
+pub const Scope = struct {
+    parent: ?*Scope,
+    env: Environment,
+
+    allocator: *std.mem.Allocator,
+
+    pub fn create(allocator: *std.mem.Allocator, parent: ?*Scope) !*Scope {
+        var scope = try allocator.create(Scope);
+
+        scope.* = Scope{
+            .parent = scope,
+            .env = Environment.init(allocator),
+            .allocator = allocator,
+        };
+        return scope;
+    }
+
+    pub fn createChild(self: *@This()) !*Scope {
+        return try @This().create(self.allocator, self);
+    }
+
+    pub fn deinit(self: *const @This()) void {
+        self.env.deinit();
+    }
 };
 
 // functions, for our purposes, other than symbols, have:
@@ -45,12 +66,7 @@ pub const FunctionSymbol = struct {
     /// Parameters for a function are also a table instead of an ArrayList
     /// because we want to resolve identifiers to them.
     parameters: UnderlyingTypeMap,
-
-    // TODO rm
-    symbols: SymbolTable,
-
-    // use this instead
-    //env: *Environment,
+    scope: *Scope,
 
     /// Find a given identifier in the function. Can resolve to either a parameter
     pub fn findSymbol(self: *const @This(), identifier: []const u8) ?SymbolData {
@@ -103,6 +119,9 @@ pub const CompilationContext = struct {
     allocator: *std.mem.Allocator,
     symbol_table: SymbolTable,
 
+    current_function: ?*FunctionSymbol = null,
+    current_scope: ?*Scope = null,
+
     pub fn init(allocator: *std.mem.Allocator) CompilationContext {
         return CompilationContext{
             .allocator = allocator,
@@ -110,6 +129,30 @@ pub const CompilationContext = struct {
         };
     }
 
+    /// Create a new scope out of the current one and set it as the current.
+    pub fn bumpScope(self: *@This()) !void {
+        if (self.current_scope == null) {
+            @panic("can't bump scope from null");
+        }
+
+        var child = try self.current_scope.?.createChild();
+        self.current_scope = child;
+    }
+
+    /// Set a given scope as the current scope.
+    pub fn setScope(self: *@This(), scope: *Scope) void {
+        self.current_scope = scope;
+    }
+
+    /// "dump" the current scope, making the new current scope be its parent.
+    pub fn dumpScope(self: *@This()) void {
+        if (self.current_scope == null) {
+            @panic("can't dump scope from null");
+        }
+
+        self.current_scope = self.current_scope.?.parent;
+    }
+
     /// Solve a given type as a string into a SymbolUnderlyingTypeEnum
     /// This does not help if you want a full SymbolUnderlyingType, use
     /// solveType() for that.
@@ -157,7 +200,7 @@ pub const CompilationContext = struct {
         decl: ast.FnDecl,
         ret_type: SymbolUnderlyingType,
         param_types: TypeList,
-        symbols: SymbolTable,
+        scope: *Scope,
     ) !void {
         var type_map = UnderlyingTypeMap.init(self.allocator);
 
@@ -170,7 +213,7 @@ pub const CompilationContext = struct {
                 .decl = decl,
                 .return_type = ret_type,
                 .parameters = type_map,
-                .symbols = symbols,
+                .scope = scope,
             },
         });
     }
diff --git a/src/types.zig b/src/types.zig
index f5f031e..1d5cae0 100644
--- a/src/types.zig
+++ b/src/types.zig
@@ -262,12 +262,24 @@ pub const TypeSolver = struct {
                     try parameters.append(param_type.?);
                 }
 
-                // TODO scopes: bump scope
+                // for a function, we always create a new root scope for it
+                // and force-set it into the current context
+                var scope = try comp.Scope.create(self.allocator, null);
+                errdefer scope.deinit();
+
+                // we must always start from a null current scope,
+                // functions inside functions are not allowed
+                std.debug.assert(ctx.current_scope == null);
+                ctx.setScope(scope);
 
                 for (decl.body.toSlice()) |stmt| {
                     try self.stmtPass(ctx, stmt);
                 }
 
+                // it should be null when we dump from a function. always
+                ctx.dumpScope();
+                std.debug.assert(ctx.current_scope == null);
+
                 // TODO scopes: down scope
 
                 // TODO symbols and scope resolution, that's
@@ -278,7 +290,7 @@ pub const TypeSolver = struct {
                 // and everything else
 
                 if (ret_type != null and parameters.len == decl.params.len) {
-                    try ctx.insertFn(decl, ret_type.?, parameters, symbols);
+                    try ctx.insertFn(decl, ret_type.?, parameters, scope);
                 }
             },