Add closure expressions to Rust AST

6 files changed, 163 insertions, 1 deletions

diff --git a/hobgoblin/src/output/lang/rust/ast.hob b/hobgoblin/src/output/lang/rust/ast.hob
index d1c7097..18b5978 100644
--- a/hobgoblin/src/output/lang/rust/ast.hob
+++ b/hobgoblin/src/output/lang/rust/ast.hob
@@ -127,6 +127,7 @@ sum RustExpression {
     variant RustBlockExpression;
     variant RustBoolLiteral;
     variant RustCallExpression;
+    variant RustClosureExpression;
     variant RustFieldExpression;
     variant RustIfExpression;
     variant RustIntegerLiteral;
@@ -177,6 +178,11 @@ struct RustCallExpression {
     field args: List[RustExpression];
 }
 
+struct RustClosureExpression {
+    field params: List[RustPattern];
+    field body: RustExpression;
+}
+
 struct RustFieldExpression {
     field containerOperand: RustExpression;
     field fieldName: RustIdentifier;
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriter.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriter.java
index 3f3f3d8..d894253 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriter.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriter.java
@@ -335,6 +335,10 @@ public class RustWriter implements AutoCloseable {
                 this.writeCallExpression(callExpression);
             }
 
+            case RustClosureExpression closureExpression -> {
+                this.writeClosureExpression(closureExpression);
+            }
+
             case RustFieldExpression fieldExpression -> {
                 this.writeFieldExpression(fieldExpression);
             }
@@ -414,6 +418,7 @@ public class RustWriter implements AutoCloseable {
             case RustBlockExpression _ -> RustPrecedence.PRIMARY;
             case RustBoolLiteral _ -> RustPrecedence.PRIMARY;
             case RustCallExpression _ -> RustPrecedence.FUNCTION_CALLS;
+            case RustClosureExpression _ -> RustPrecedence.PRIMARY;
             case RustFieldExpression _ -> RustPrecedence.FIELD_EXPRESSIONS;
             case RustIfExpression _ -> RustPrecedence.PRIMARY;
             case RustIntegerLiteral _ -> RustPrecedence.PRIMARY;
@@ -522,6 +527,25 @@ public class RustWriter implements AutoCloseable {
         this.writer.write(")");
     }
 
+    private void writeClosureExpression(
+        RustClosureExpression closureExpression
+    ) throws IOException {
+        this.writer.write("|");
+
+        writeWithSeparator(
+            closureExpression.params(),
+            this::writePattern,
+            () -> {
+                this.writer.write(", ");
+            }
+        );
+
+        this.writer.write("| ");
+
+        this.writeTopLevelExpression(closureExpression.body());
+    }
+
+
     private void writeFieldExpression(RustFieldExpression fieldExpression) throws IOException {
         this.writeSubExpression(fieldExpression.containerOperand(), precedence(fieldExpression), true);
         this.writer.write(".");
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustClosureExpression.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustClosureExpression.java
new file mode 100644
index 0000000..2322750
--- /dev/null
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustClosureExpression.java
@@ -0,0 +1,48 @@
+// Generated by hobgoblin.
+
+package org.zwobble.hobgoblin.compiler.output.lang.rust.ast;
+
+// Custom area start: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression imports
+// Custom area end: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression imports
+
+public record RustClosureExpression(java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustPattern> params, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustExpression body) implements org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustExpression {
+    public static org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression.Builder arbitrary() {
+        return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression.Builder(java.util.List.of(), org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustBlockExpression.arbitrary().build());
+    }
+
+    public record Builder(java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustPattern> params, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustExpression body) implements org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustExpression.Builder {
+        public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression build() {
+            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression(params, body);
+        }
+
+        public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression.Builder withParams(java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustPattern> params) {
+            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression.Builder(params, body);
+        }
+
+        public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression.Builder addParam(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustPattern param) {
+            var params = new java.util.ArrayList<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustPattern>(this.params);
+            params.add(param);
+            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression.Builder(params, body);
+        }
+
+        public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression.Builder addParam(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustPattern.Builder param) {
+            var params = new java.util.ArrayList<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustPattern>(this.params);
+            params.add(param.build());
+            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression.Builder(params, body);
+        }
+
+        public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression.Builder withBody(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustExpression body) {
+            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression.Builder(params, body);
+        }
+
+        public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression.Builder withBody(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustExpression.Builder body) {
+            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression.Builder(params, body.build());
+        }
+
+        // Custom area start: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression.Builder body
+        // Custom area end: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression.Builder body
+    }
+
+    // Custom area start: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression body
+    // Custom area end: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression body
+}
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustExpression.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustExpression.java
index 8e55bc4..5f51d5e 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustExpression.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustExpression.java
@@ -5,7 +5,7 @@ package org.zwobble.hobgoblin.compiler.output.lang.rust.ast;
 // Custom area start: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustExpression imports
 // Custom area end: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustExpression imports
 
-public sealed interface RustExpression permits org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustArrayRepeatExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustBinaryExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustBlockExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustBoolLiteral, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustCallExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustFieldExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustIfExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustIntegerLiteral, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustIteratorLoopExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustMatchExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustPath, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustPrefixExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustRangeExpr, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustTryPropagationExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustTupleExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustVecRepeatExpression {
+public sealed interface RustExpression permits org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustArrayRepeatExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustBinaryExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustBlockExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustBoolLiteral, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustCallExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustFieldExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustIfExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustIntegerLiteral, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustIteratorLoopExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustMatchExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustPath, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustPrefixExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustRangeExpr, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustTryPropagationExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustTupleExpression, org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustVecRepeatExpression {
     public interface Builder {
         public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustExpression build();
 
diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriterTests.java b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriterTests.java
index 1d04b72..481d99e 100644
--- a/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriterTests.java
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriterTests.java
@@ -564,6 +564,45 @@ public class RustWriterTests {
         assertThat(string, equalTo("f(x, y)"));
     }
 
+    // === Closure expressions ===
+
+    @Test
+    public void closureExpressionWithNoParams() throws IOException {
+        var rust = RustClosureExpression.arbitrary()
+            .withBody(RustPath.of("a"))
+            .build();
+
+        var string = write(writer -> writer.writeTopLevelExpression(rust));
+
+        assertThat(string, equalTo("|| a"));
+    }
+
+    @Test
+    public void closureExpressionWithOneParam() throws IOException {
+        var rust = RustClosureExpression.arbitrary()
+            .addParam(RustIdentifierPattern.arbitrary().withVariableName(RustIdentifier.of("a")))
+            .withBody(RustPath.of("a"))
+            .build();
+
+        var string = write(writer -> writer.writeTopLevelExpression(rust));
+
+        assertThat(string, equalTo("|a| a"));
+    }
+
+    @Test
+    public void closureExpressionWithMultipleParams() throws IOException {
+        var rust = RustClosureExpression.arbitrary()
+            .addParam(RustIdentifierPattern.arbitrary().withVariableName(RustIdentifier.of("a")))
+            .addParam(RustIdentifierPattern.arbitrary().withVariableName(RustIdentifier.of("b")))
+            .addParam(RustIdentifierPattern.arbitrary().withVariableName(RustIdentifier.of("c")))
+            .withBody(RustPath.of("a"))
+            .build();
+
+        var string = write(writer -> writer.writeTopLevelExpression(rust));
+
+        assertThat(string, equalTo("|a, b, c| a"));
+    }
+
     // === Field expressions ===
 
     @Test
diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustClosureExpressionMatcher.java b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustClosureExpressionMatcher.java
new file mode 100644
index 0000000..d50cc13
--- /dev/null
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustClosureExpressionMatcher.java
@@ -0,0 +1,45 @@
+// Generated by hobgoblin.
+
+package org.zwobble.hobgoblin.compiler.output.lang.rust.ast;
+
+// Custom area start: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpressionMatcher imports
+// Custom area end: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpressionMatcher imports
+
+public class RustClosureExpressionMatcher implements org.zwobble.precisely.Matcher<java.lang.Object> {
+    public static org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpressionMatcher isRustClosureExpression() {
+        return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpressionMatcher(java.util.List.of());
+    }
+
+    private final java.util.List<org.zwobble.precisely.Matcher<? super org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression>> submatchers;
+
+    private RustClosureExpressionMatcher(java.util.List<org.zwobble.precisely.Matcher<? super org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression>> submatchers) {
+        this.submatchers = submatchers;
+    }
+
+    public org.zwobble.precisely.MatchResult match(java.lang.Object actual) {
+        return this.toMatcher().match(actual);
+    }
+
+    public org.zwobble.precisely.TextTree describe() {
+        return this.toMatcher().describe();
+    }
+
+    private org.zwobble.precisely.Matcher<java.lang.Object> toMatcher() {
+        return org.zwobble.precisely.Matchers.instanceOf(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression.class, this.submatchers);
+    }
+
+    public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpressionMatcher withParams(org.zwobble.precisely.Matcher<? super java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustPattern>> params) {
+        var submatchers = new java.util.ArrayList<org.zwobble.precisely.Matcher<? super org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression>>(this.submatchers);
+        submatchers.add(org.zwobble.precisely.Matchers.has("params", org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression::params, params));
+        return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpressionMatcher(submatchers);
+    }
+
+    public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpressionMatcher withBody(org.zwobble.precisely.Matcher<? super org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustExpression> body) {
+        var submatchers = new java.util.ArrayList<org.zwobble.precisely.Matcher<? super org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression>>(this.submatchers);
+        submatchers.add(org.zwobble.precisely.Matchers.has("body", org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpression::body, body));
+        return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpressionMatcher(submatchers);
+    }
+
+    // Custom area start: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpressionMatcher body
+    // Custom area end: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustClosureExpressionMatcher body
+}