From ee3d75f1f230ae05803db83ce387eb8b79bc1d95 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Mon, 31 Jul 2023 22:13:28 +0100
Subject: Extract Variable to be top-level interface

---
 .../compiler/typechecker/EnvironmentBuilder.java      | 10 +++++-----
 .../shedlang/compiler/typechecker/TypeChecker.java    | 10 +++++-----
 .../compiler/typechecker/TypeCheckerContext.java      | 15 +--------------
 .../org/shedlang/compiler/typechecker/Variable.java   | 19 +++++++++++++++++++
 4 files changed, 30 insertions(+), 24 deletions(-)
 create mode 100644 src/main/java/org/shedlang/compiler/typechecker/Variable.java

(limited to 'src/main/java')

diff --git a/src/main/java/org/shedlang/compiler/typechecker/EnvironmentBuilder.java b/src/main/java/org/shedlang/compiler/typechecker/EnvironmentBuilder.java
index 53853305..c30c745a 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/EnvironmentBuilder.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/EnvironmentBuilder.java
@@ -11,9 +11,9 @@ import java.util.List;
 public class EnvironmentBuilder {
     public static final EnvironmentBuilder EMPTY = new EnvironmentBuilder(Empty.map());
 
-    private PMap<String, TypeCheckerContext.Variable> environment;
+    private PMap<String, Variable> environment;
 
-    private EnvironmentBuilder(PMap<String, TypeCheckerContext.Variable> environment) {
+    private EnvironmentBuilder(PMap<String, Variable> environment) {
         this.environment = environment;
     }
 
@@ -31,17 +31,17 @@ public class EnvironmentBuilder {
         if (environment.containsKey(name)) {
             throw new DuplicateVariableName(name, source);
         }
-        return new EnvironmentBuilder(environment.plus(name, new TypeCheckerContext.Variable.Undefined()));
+        return new EnvironmentBuilder(environment.plus(name, new Variable.Undefined()));
     }
 
-    public EnvironmentBuilder add(String name, TypeCheckerContext.Variable variable, Source source) {
+    public EnvironmentBuilder add(String name, Variable variable, Source source) {
         if (environment.containsKey(name)) {
             throw new DuplicateVariableName(name, source);
         }
         return new EnvironmentBuilder(environment.plus(name, variable));
     }
 
-    public PMap<String, TypeCheckerContext.Variable> build() {
+    public PMap<String, Variable> build() {
         return environment;
     }
 
diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
index ee35fa1f..5377f562 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
@@ -49,10 +49,10 @@ public class TypeChecker {
         }
 
         return switch (type.get()) {
-            case TypeCheckerContext.Variable.Defined defined ->
+            case Variable.Defined defined ->
                 defined.type();
 
-            case TypeCheckerContext.Variable.Undefined undefined ->
+            case Variable.Undefined undefined ->
                 throw new ReferenceBeforeDefinitionError(name, source);
         };
     }
@@ -64,10 +64,10 @@ public class TypeChecker {
             }
 
             return switch (type.get()) {
-                case TypeCheckerContext.Variable.Defined defined ->
+                case Variable.Defined defined ->
                     defined.type();
 
-                case TypeCheckerContext.Variable.Undefined undefined ->
+                case Variable.Undefined undefined ->
                     throw new ReferenceBeforeDefinitionError(name, source);
             };
         });
@@ -458,7 +458,7 @@ public class TypeChecker {
         for (var param : typedParams.all()) {
             bodyEnvironment = bodyEnvironment.add(
                 param.name(),
-                TypeCheckerContext.defined(param.type().value()),
+                Variable.defined(param.type().value()),
                 param.source()
             );
         }
diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeCheckerContext.java b/src/main/java/org/shedlang/compiler/typechecker/TypeCheckerContext.java
index d6a10d35..30778094 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeCheckerContext.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeCheckerContext.java
@@ -30,19 +30,6 @@ public class TypeCheckerContext {
         ))
     );
 
-    public sealed interface Variable {
-        record Undefined() implements Variable {}
-        record Defined(Type type) implements Variable {}
-    }
-
-    public static Variable defined(Type type) {
-        return new Variable.Defined(type);
-    }
-
-    public static Variable undefined() {
-        return new Variable.Undefined();
-    }
-
     private sealed interface StackElement {
         boolean isBoundInElement(String name);
         StackElement withFreeVariable(String name, Source referenceSource);
@@ -152,7 +139,7 @@ public class TypeCheckerContext {
 
     public TypeCheckerContext enterNamespaceWithDefinedVariables(PMap<String, Type> variables) {
         var environment = variables.entrySet().stream()
-            .map(x -> Map.entry(x.getKey(), TypeCheckerContext.defined(x.getValue())))
+            .map(x -> Map.entry(x.getKey(), Variable.defined(x.getValue())))
             .collect(PCollectors.toMap());
 
         return enterNamespace(environment);
diff --git a/src/main/java/org/shedlang/compiler/typechecker/Variable.java b/src/main/java/org/shedlang/compiler/typechecker/Variable.java
new file mode 100644
index 00000000..7fd7ca23
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/typechecker/Variable.java
@@ -0,0 +1,19 @@
+package org.shedlang.compiler.typechecker;
+
+import org.shedlang.compiler.types.Type;
+
+public sealed interface Variable {
+    static Variable defined(Type type) {
+        return new Variable.Defined(type);
+    }
+
+    static Variable undefined() {
+        return new Variable.Undefined();
+    }
+
+    record Undefined() implements Variable {
+    }
+
+    record Defined(Type type) implements Variable {
+    }
+}
-- 
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