Introduce explicit notion of a BoundVariable

8 files changed, 61 insertions, 52 deletions

diff --git a/src/main/java/org/shedlang/compiler/ast/typed/BoundVariable.java b/src/main/java/org/shedlang/compiler/ast/typed/BoundVariable.java
new file mode 100644
index 00000000..dcd2d113
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/ast/typed/BoundVariable.java
@@ -0,0 +1,7 @@
+package org.shedlang.compiler.ast.typed;
+
+public record BoundVariable(String name) {
+    public static BoundVariable immutable(String name) {
+        return new BoundVariable(name);
+    }
+}
diff --git a/src/main/java/org/shedlang/compiler/ast/typed/TypedBlockNode.java b/src/main/java/org/shedlang/compiler/ast/typed/TypedBlockNode.java
index 9753f974..2b06755c 100644
--- a/src/main/java/org/shedlang/compiler/ast/typed/TypedBlockNode.java
+++ b/src/main/java/org/shedlang/compiler/ast/typed/TypedBlockNode.java
@@ -8,13 +8,13 @@ import org.shedlang.compiler.util.Lists;
 import java.util.List;
 
 /**
- * @param boundVariableNames The names of variables that are bound in the
- *                           block's scope, not including any children scopes
- *                           such as the bodies of <code>if</code> expressions.
+ * @param boundVariables The variables that are bound in the block's scope, not
+ *                       including any children scopes such as the bodies of
+ *                       <code>if</code> expressions.
  */
 public record TypedBlockNode(
     List<? extends TypedFunctionStatementNode> statements,
-    List<String> boundVariableNames,
+    List<BoundVariable> boundVariables,
     Source source
 ) implements TypedNode {
     public TypedFunctionStatementBehaviour behaviour() {
diff --git a/src/main/java/org/shedlang/compiler/ast/typed/TypedFunctionBodyNode.java b/src/main/java/org/shedlang/compiler/ast/typed/TypedFunctionBodyNode.java
index 01225d71..cae9cf43 100644
--- a/src/main/java/org/shedlang/compiler/ast/typed/TypedFunctionBodyNode.java
+++ b/src/main/java/org/shedlang/compiler/ast/typed/TypedFunctionBodyNode.java
@@ -11,8 +11,8 @@ public record TypedFunctionBodyNode(
     Type type,
     Source source
 ) implements TypedNode {
-    public List<String> boundVariableNames() {
-        return block.boundVariableNames();
+    public List<BoundVariable> boundVariables() {
+        return block.boundVariables();
     }
 
     public TypedFunctionStatementBehaviour behaviour() {
diff --git a/src/main/java/org/shedlang/compiler/ast/typed/TypedFunctionDefinitionNode.java b/src/main/java/org/shedlang/compiler/ast/typed/TypedFunctionDefinitionNode.java
index eb664e71..c1a28516 100644
--- a/src/main/java/org/shedlang/compiler/ast/typed/TypedFunctionDefinitionNode.java
+++ b/src/main/java/org/shedlang/compiler/ast/typed/TypedFunctionDefinitionNode.java
@@ -30,7 +30,7 @@ public record TypedFunctionDefinitionNode(
         String name,
         TypedFunctionSignatureNode.Builder signature,
         FreeVariables.Builder freeVariables,
-        PVector<String> boundVariableNames,
+        PVector<BoundVariable> boundVariables,
         PVector<TypedFunctionStatementNode> body,
         FunctionType type
     ) {
@@ -40,7 +40,7 @@ public record TypedFunctionDefinitionNode(
                 signature.build(),
                 new TypedFunctionBodyNode(
                     freeVariables.build(),
-                    new TypedBlockNode(body, boundVariableNames, Sources.NULL),
+                    new TypedBlockNode(body, boundVariables, Sources.NULL),
                     Types.UNIT,
                     Sources.NULL
                 ),
@@ -54,7 +54,7 @@ public record TypedFunctionDefinitionNode(
                 name,
                 this.signature,
                 this.freeVariables,
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body,
                 this.type
             );
@@ -65,10 +65,10 @@ public record TypedFunctionDefinitionNode(
                 this.name,
                 this.signature.addPositionalParam(name, type),
                 this.freeVariables,
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body,
                 this.type
-            ).addBoundVariable(name);
+            ).addBoundVariable(BoundVariable.immutable(name));
         }
 
         public TypedFunctionDefinitionNode.Builder addNamedParam(String name, TypedTypeLevelExpressionNode<Type> type) {
@@ -76,10 +76,10 @@ public record TypedFunctionDefinitionNode(
                 this.name,
                 this.signature.addNamedParam(name, type),
                 this.freeVariables,
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body,
                 this.type
-            ).addBoundVariable(name);
+            ).addBoundVariable(BoundVariable.immutable(name));
         }
 
         public TypedFunctionDefinitionNode.Builder withEffect(TypedTypeLevelExpressionNode<Effect> effect) {
@@ -87,7 +87,7 @@ public record TypedFunctionDefinitionNode(
                 this.name,
                 this.signature.withEffect(effect),
                 this.freeVariables,
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body,
                 this.type
             );
@@ -98,7 +98,7 @@ public record TypedFunctionDefinitionNode(
                 this.name,
                 this.signature.withReturnType(returnType),
                 this.freeVariables,
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body,
                 this.type
             );
@@ -109,18 +109,18 @@ public record TypedFunctionDefinitionNode(
                 this.name,
                 this.signature,
                 this.freeVariables.plus(freeVariable, Sources.NULL),
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body,
                 this.type
             );
         }
 
-        public Builder addBoundVariable(String name) {
+        public Builder addBoundVariable(BoundVariable boundVariable) {
             return new TypedFunctionDefinitionNode.Builder(
                 this.name,
                 this.signature,
                 this.freeVariables,
-                this.boundVariableNames.plus(name),
+                this.boundVariables.plus(boundVariable),
                 this.body,
                 this.type
             );
@@ -131,7 +131,7 @@ public record TypedFunctionDefinitionNode(
                 this.name,
                 this.signature,
                 this.freeVariables,
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body.plus(statement),
                 this.type
             );
diff --git a/src/main/java/org/shedlang/compiler/ast/typed/TypedFunctionExpressionNode.java b/src/main/java/org/shedlang/compiler/ast/typed/TypedFunctionExpressionNode.java
index e11c35d0..fd53a26d 100644
--- a/src/main/java/org/shedlang/compiler/ast/typed/TypedFunctionExpressionNode.java
+++ b/src/main/java/org/shedlang/compiler/ast/typed/TypedFunctionExpressionNode.java
@@ -27,7 +27,7 @@ public record TypedFunctionExpressionNode(
     public record Builder(
         TypedFunctionSignatureNode.Builder signature,
         FreeVariables.Builder freeVariables,
-        PVector<String> boundVariableNames,
+        PVector<BoundVariable> boundVariables,
         PVector<TypedFunctionStatementNode> body,
         FunctionType type
     ) {
@@ -36,7 +36,7 @@ public record TypedFunctionExpressionNode(
                 signature.build(),
                 new TypedFunctionBodyNode(
                     freeVariables.build(),
-                    new TypedBlockNode(body, boundVariableNames, Sources.NULL),
+                    new TypedBlockNode(body, boundVariables, Sources.NULL),
                     Types.UNIT,
                     Sources.NULL
                 ),
@@ -49,27 +49,27 @@ public record TypedFunctionExpressionNode(
             return new Builder(
                 this.signature.addPositionalParam(name, type),
                 this.freeVariables,
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body,
                 this.type
-            ).addBoundVariable(name);
+            ).addBoundVariable(BoundVariable.immutable(name));
         }
 
         public Builder addNamedParam(String name, TypedTypeLevelExpressionNode<Type> type) {
             return new Builder(
                 this.signature.addNamedParam(name, type),
                 this.freeVariables,
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body,
                 this.type
-            ).addBoundVariable(name);
+            ).addBoundVariable(BoundVariable.immutable(name));
         }
 
         public Builder withEffect(TypedTypeLevelExpressionNode<Effect> effect) {
             return new Builder(
                 this.signature.withEffect(effect),
                 this.freeVariables,
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body,
                 this.type
             );
@@ -79,7 +79,7 @@ public record TypedFunctionExpressionNode(
             return new Builder(
                 this.signature.withReturnType(returnType),
                 this.freeVariables,
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body,
                 this.type
             );
@@ -89,17 +89,17 @@ public record TypedFunctionExpressionNode(
             return new Builder(
                 this.signature,
                 this.freeVariables.plus(freeVariable, Sources.NULL),
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body,
                 this.type
             );
         }
 
-        public Builder addBoundVariable(String name) {
+        public Builder addBoundVariable(BoundVariable boundVariable) {
             return new Builder(
                 this.signature,
                 this.freeVariables,
-                this.boundVariableNames.plus(name),
+                this.boundVariables.plus(boundVariable),
                 this.body,
                 this.type
             );
@@ -109,7 +109,7 @@ public record TypedFunctionExpressionNode(
             return new Builder(
                 this.signature,
                 this.freeVariables,
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body.plus(statement),
                 this.type
             );
diff --git a/src/main/java/org/shedlang/compiler/ast/typed/TypedTryHandlerMethodNode.java b/src/main/java/org/shedlang/compiler/ast/typed/TypedTryHandlerMethodNode.java
index 14253c67..e9cbd4d8 100644
--- a/src/main/java/org/shedlang/compiler/ast/typed/TypedTryHandlerMethodNode.java
+++ b/src/main/java/org/shedlang/compiler/ast/typed/TypedTryHandlerMethodNode.java
@@ -30,7 +30,7 @@ public record TypedTryHandlerMethodNode(
         String name,
         TypedFunctionSignatureNode.Builder signature,
         FreeVariables.Builder freeVariables,
-        PVector<String> boundVariableNames,
+        PVector<BoundVariable> boundVariables,
         PVector<TypedFunctionStatementNode> body,
         FunctionType type
     ) {
@@ -40,7 +40,7 @@ public record TypedTryHandlerMethodNode(
                 signature.build().params(),
                 new TypedFunctionBodyNode(
                     freeVariables.build(),
-                    new TypedBlockNode(body, boundVariableNames, Sources.NULL),
+                    new TypedBlockNode(body, boundVariables, Sources.NULL),
                     Types.UNIT,
                     Sources.NULL
                 ),
@@ -54,7 +54,7 @@ public record TypedTryHandlerMethodNode(
                 name,
                 this.signature,
                 this.freeVariables,
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body,
                 this.type
             );
@@ -65,10 +65,10 @@ public record TypedTryHandlerMethodNode(
                 this.name,
                 this.signature.addPositionalParam(name, type),
                 this.freeVariables,
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body,
                 this.type
-            ).addBoundVariable(name);
+            ).addBoundVariable(BoundVariable.immutable(name));
         }
 
         public TypedTryHandlerMethodNode.Builder addNamedParam(String name, TypedTypeLevelExpressionNode<Type> type) {
@@ -76,10 +76,10 @@ public record TypedTryHandlerMethodNode(
                 this.name,
                 this.signature.addNamedParam(name, type),
                 this.freeVariables,
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body,
                 this.type
-            ).addBoundVariable(name);
+            ).addBoundVariable(BoundVariable.immutable(name));
         }
 
         public Builder addFreeVariable(String freeVariable) {
@@ -87,18 +87,18 @@ public record TypedTryHandlerMethodNode(
                 this.name,
                 this.signature,
                 this.freeVariables.plus(freeVariable, Sources.NULL),
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body,
                 this.type
             );
         }
 
-        public Builder addBoundVariable(String name) {
+        public Builder addBoundVariable(BoundVariable boundVariable) {
             return new TypedTryHandlerMethodNode.Builder(
                 this.name,
                 this.signature,
                 this.freeVariables,
-                this.boundVariableNames.plus(name),
+                this.boundVariables.plus(boundVariable),
                 this.body,
                 this.type
             );
@@ -109,7 +109,7 @@ public record TypedTryHandlerMethodNode(
                 this.name,
                 this.signature,
                 this.freeVariables,
-                this.boundVariableNames,
+                this.boundVariables,
                 this.body.plus(statement),
                 this.type
             );
diff --git a/src/main/java/org/shedlang/compiler/stackir/StackCompiler.java b/src/main/java/org/shedlang/compiler/stackir/StackCompiler.java
index 8110e6da..885e26e4 100644
--- a/src/main/java/org/shedlang/compiler/stackir/StackCompiler.java
+++ b/src/main/java/org/shedlang/compiler/stackir/StackCompiler.java
@@ -217,7 +217,7 @@ public class StackCompiler {
         Source source,
         Context context
     ) {
-        context = context.enterBlock(body.boundVariableNames());
+        context = context.enterBlock(body.boundVariables());
 
         var c = context;
 
@@ -355,7 +355,7 @@ public class StackCompiler {
         Context context
     ) {
         if (conditionalBranches.isEmpty()) {
-            context = context.enterBlock(elseBody.boundVariableNames());
+            context = context.enterBlock(elseBody.boundVariables());
             context = compileBlockWithYield(elseBody, context);
             var elseInstructions = context.instructions;
             context = context.exitBlock();
@@ -366,7 +366,7 @@ public class StackCompiler {
             var conditionalBranch = conditionalBranches.get(0);
             context = compileExpression(conditionalBranch.condition(), context);
 
-            context = context.enterBlock(conditionalBranch.body().boundVariableNames());
+            context = context.enterBlock(conditionalBranch.body().boundVariables());
             context = compileBlockWithYield(conditionalBranch.body(), context);
             var ifTrueInstructions = context.instructions;
             context = context.exitBlock();
@@ -622,7 +622,7 @@ public class StackCompiler {
             context = compileTryHandlerMethod(handlerMethod, context);
         }
 
-        context = context.enterBlock(node.body().boundVariableNames());
+        context = context.enterBlock(node.body().boundVariables());
         context = compileBlockWithYield(node.body(), context);
         var bodyInstructions = context.instructions;
         context = context.exitBlock();
@@ -674,7 +674,7 @@ public class StackCompiler {
         var switchCases = new ArrayList<SwitchInstruction.Case>();
 
         for (var whenCase : node.cases()) {
-            context = context.enterBlock(whenCase.body().boundVariableNames());
+            context = context.enterBlock(whenCase.body().boundVariables());
             context = compileBlockWithYield(whenCase.body(), context);
             var caseBodyInstructions = context.instructions;
             context = context.exitBlock();
@@ -696,7 +696,7 @@ public class StackCompiler {
     }
 
     private static Context compileWhile(TypedWhileNode node, Context context) {
-        context = context.enterBlock(node.body().boundVariableNames());
+        context = context.enterBlock(node.body().boundVariables());
         context = compileBlockWithoutYield(node.body(), context);
         var ifTrueInstructions = context.instructions;
         context = context.exitBlock();
@@ -754,7 +754,7 @@ public class StackCompiler {
             this.shedVariablesByName = shedVariablesByName;
         }
 
-        public Context enterBlock(List<String> shedVariableNames) {
+        public Context enterBlock(List<BoundVariable> shedVariables) {
             var context = new Context(
                 this.instructionsStack.plus(this.instructions),
                 P.vector(),
@@ -763,8 +763,8 @@ public class StackCompiler {
                 this.shedVariablesByName
             );
 
-            for (var shedVariableName : shedVariableNames) {
-                context = context.addShedVariable(shedVariableName);
+            for (var shedVariable : shedVariables) {
+                context = context.addShedVariable(shedVariable.name());
             }
 
             return context;
diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
index 9963ee56..1ea3b680 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
@@ -225,7 +225,9 @@ public class TypeChecker {
 
         var typed = new TypedBlockNode(
             typedStatements,
-            declaredVariableNames,
+            declaredVariableNames.stream()
+                .map(BoundVariable::new)
+                .toList(),
             untyped.source()
         );