3 files changed, 164 insertions, 0 deletions

diff --git a/checker/src/main/java/lv/enes/orang/checker/Checker.java b/checker/src/main/java/lv/enes/orang/checker/Checker.java
new file mode 100644
index 0000000..446d3f1
--- /dev/null
+++ b/checker/src/main/java/lv/enes/orang/checker/Checker.java
@@ -0,0 +1,146 @@
+package lv.enes.orang.checker;
+
+import lv.enes.orang.ast.*;
+import lv.enes.orang.core.ImmutableScope;
+import lv.enes.orang.core.Scope;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class Checker implements ExpressionVisitor<Void, CheckerException>, StatementVisitor<Checker, CheckerException> {
+        private final Scope<Boolean> definitions;
+
+        public static <E> Checker of(Map<String, E> builtins) {
+                var boolMap = builtins.keySet()
+                                .stream()
+                                .<Map<String, Boolean>>collect(
+                                                HashMap::new,
+                                                (map, elem) -> map.put(elem, true),
+                                                Map::putAll
+                                );
+                return new Checker(ImmutableScope.of(boolMap));
+        }
+
+        private Checker(Scope<Boolean> definitions) {
+                this.definitions = definitions;
+        }
+
+        @Override
+        public Void visitArray(ArrayExpression array) throws CheckerException {
+                for (var expr : array.items()) {
+                        visit(expr);
+                }
+                return null;
+        }
+
+        @Override
+        public Void visitBoolean(BooleanLiteral expr) {
+                // Always ok
+                return null;
+        }
+
+        @Override
+        public Void visitBinaryExpression(BinaryExpression expr) throws CheckerException {
+                visit(expr.lhs());
+                visit(expr.rhs());
+                return null;
+        }
+
+        @Override
+        public Void visitCallExpression(CallExpression expr) throws CheckerException {
+                visit(expr.callee());
+                visit(expr.arg());
+                return null;
+        }
+
+        @Override
+        public Checker visitDefinition(Definition def) throws CheckerException {
+                if (definitions.hasDefinition(def.name())) {
+                        throw new CheckerException(STR."Top-level definition '\{def.name()}' redefined!");
+                }
+                return new Checker(ImmutableScope.of(definitions, def.name(), true));
+        }
+
+        @Override
+        public Void visitDoExpression(DoExpression expr) throws CheckerException {
+                for (var child : expr.body()) {
+                        visit(child);
+                }
+                return null;
+        }
+
+        @Override
+        public Checker visitExpression(ExpressionStatement expr) throws CheckerException {
+                visit(expr.expr());
+                return this;
+        }
+
+        @Override
+        public Void visitFnExpression(FnExpression expr) throws CheckerException {
+                var args = new HashMap<String, Boolean>();
+                for (var arg : expr.args()) {
+                        args.put(arg.name, true);
+                }
+                new Checker(ImmutableScope.of(definitions, args)).visit(expr.body());
+                return null;
+        }
+
+        @Override
+        public Void visitIfElseExpression(IfElseExpression expr) throws CheckerException {
+                visit(expr.condition());
+                visit(expr.trueBranch());
+                visit(expr.falseBranch());
+                return null;
+        }
+
+        @Override
+        public Void visitIntLiteral(IntLiteral expr) {
+                // Always ok
+                return null;
+        }
+
+        @Override
+        public Void visitLetInExpression(LetInExpression expr) throws CheckerException {
+                var locals = new HashMap<String, Boolean>();
+                for (var local : expr.bindings()) {
+                        locals.put(local.name(), true);
+                }
+                new Checker(ImmutableScope.of(definitions, locals)).visit(expr.body());
+                return null;
+        }
+
+        @Override
+        public Checker visitProgram(Program program) throws CheckerException {
+                var checker = this;
+                for (var stmt : program.statements()) {
+                        checker = checker.visit(stmt);
+                }
+                return checker;
+        }
+
+        @Override
+        public Void visitStringLiteral(StringLiteral expr) {
+                // Always ok
+                return null;
+        }
+
+        @Override
+        public Void visitUnaryExpression(UnaryExpression expr) throws CheckerException {
+                visit(expr.child());
+                return null;
+        }
+
+        @Override
+        public Void visitVariable(VariableExpression expr) throws CheckerException {
+                if (!definitions.hasDefinition(expr.name())) {
+                        throw new CheckerException(STR."Variable named '\{expr.name()}' not defined!");
+                }
+                return null;
+        }
+
+        @Override
+        public Void visitVoidExpression() {
+                // Always ok
+                return null;
+        }
+}
diff --git a/checker/src/main/java/lv/enes/orang/checker/CheckerException.java b/checker/src/main/java/lv/enes/orang/checker/CheckerException.java
new file mode 100644
index 0000000..9354f27
--- /dev/null
+++ b/checker/src/main/java/lv/enes/orang/checker/CheckerException.java
@@ -0,0 +1,9 @@
+package lv.enes.orang.checker;
+
+import lv.enes.orang.core.OrangException;
+
+public class CheckerException extends OrangException {
+        public CheckerException(String message) {
+                super(message);
+        }
+}
diff --git a/checker/src/main/java/module-info.java b/checker/src/main/java/module-info.java
new file mode 100644
index 0000000..6e5fa47
--- /dev/null
+++ b/checker/src/main/java/module-info.java
@@ -0,0 +1,9 @@
+module lv.enes.orang.checker {
+        exports lv.enes.orang.checker;
+
+        requires lv.enes.orang.ast;
+        requires lv.enes.orang.core;
+        requires lv.enes.orang.utils;
+
+        requires static lombok;
+}
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