Add redeclaration checks for functions and locals

Closes #1.

2 files changed, 54 insertions, 0 deletions

diff --git a/decl.go b/decl.go
new file mode 100644
index 0000000..179acb2
--- /dev/null
+++ b/decl.go
@@ -0,0 +1,28 @@
+// SPDX-FileCopyrightText: 2024 Himbeer <himbeer@disroot.org>
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package main
+
+var funcs = map[string]struct{}{}
+var localConsts = map[string]map[string]string{}
+var localMuts = map[string]map[string]struct{}{}
+
+func isDeclared(name string, toplevel bool) bool {
+	if toplevel {
+		return isDeclaredToplevel(name)
+	}
+
+	return isDeclaredLocal(currentFunc, name)
+}
+
+func isDeclaredToplevel(name string) bool {
+	_, ok := funcs[name]
+	return ok
+}
+
+func isDeclaredLocal(function string, local string) bool {
+	_, constant := localConsts[function][local]
+	_, mutable := localMuts[function][local]
+	return constant || mutable
+}
diff --git a/generate.go b/generate.go
index 3fa09f7..511ce05 100644
--- a/generate.go
+++ b/generate.go
@@ -11,6 +11,8 @@ import (
 	"strings"
 )
 
+var currentFunc string
+
 var funcRegIndex int
 
 func allocReg() string {
@@ -61,6 +63,7 @@ func generate(root *rootExpr, w io.Writer, errs chan<- error) {
 	for _, toplevel := range root.toplevels {
 		if err := generateToplevel(toplevel, w); err != nil {
 			errs <- err
+			select {}
 		}
 	}
 
@@ -77,8 +80,19 @@ func generateToplevel(toplevel expression, w io.Writer) error {
 }
 
 func generateFunction(function *functionExpr, w io.Writer) error {
+	if isDeclared(function.name, true) {
+		return errAlreadyDeclared{name: function.name, line: function.line()}
+	}
+
 	resetRegs()
 
+	currentFunc = function.name
+	defer func() { currentFunc = "" }()
+
+	funcs[currentFunc] = struct{}{}
+	localConsts[currentFunc] = map[string]string{}
+	localMuts[currentFunc] = map[string]struct{}{}
+
 	if function.link != defaultLinkage {
 		fmt.Fprintf(w, "%s ", function.link)
 	}
@@ -129,21 +143,33 @@ func generateReturnStmt(stmt *returnStmt, w io.Writer) error {
 }
 
 func generateConstStmt(stmt *constStmt, toplevel bool, w io.Writer) error {
+	if isDeclared(stmt.name, toplevel) {
+		return errAlreadyDeclared{name: stmt.name, line: stmt.line()}
+	}
+
 	value, err := stmt.initial.generate(w)
 	if err != nil {
 		return err
 	}
 
+	localConsts[currentFunc][stmt.name] = value
+
 	fmt.Fprintf(w, "%%%s =w add %s, 0\n", stmt.name, value)
 	return nil
 }
 
 func generateMutStmt(stmt *mutStmt, toplevel bool, w io.Writer) error {
+	if isDeclared(stmt.name, toplevel) {
+		return errAlreadyDeclared{name: stmt.name, line: stmt.line()}
+	}
+
 	value, err := stmt.initial.generate(w)
 	if err != nil {
 		return err
 	}
 
+	localMuts[currentFunc][stmt.name] = struct{}{}
+
 	fmt.Fprintf(w, "%%%s =l alloc4 4\n", stmt.name)
 	fmt.Fprintf(w, "storew %s, %%%s\n", value, stmt.name)
 	return nil