chore: bump version to 0.1.3

Adds spread operator for records, allowing concise record updates:
  let p2 = { ...p, x: 5.0 }

Changes across the full pipeline:
- Lexer: new DotDotDot (...) token
- AST: optional spread field on Record variant
- Parser: detect ... at start of record expression
- Typechecker: merge spread record fields with explicit overrides
- Interpreter: evaluate spread, overlay explicit fields
- JS backend: emit native JS spread syntax
- C backend: copy spread into temp, assign overrides
- Formatter, linter, LSP, symbol table: propagate spread

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -42,17 +42,45 @@ When making changes:
 7. **Fix language limitations**: If you encounter parser/type system limitations, fix them (without regressions on guarantees or speed)
 8. **Git commits**: Always use `--no-gpg-sign` flag
 
-### Post-work checklist (run after each major piece of work)
+### Post-work checklist (run after each committable change)
+
+**MANDATORY: Run the full validation script after every committable change:**
 ```bash
-nix develop --command cargo check       # No Rust errors
+./scripts/validate.sh
-nix develop --command cargo test        # All tests pass (currently 381)
-./target/release/lux check              # Type check + lint all .lux files
-./target/release/lux fmt                # Format all .lux files
-./target/release/lux lint               # Standalone lint pass
 ```
 
+This script runs ALL of the following checks and will fail if any regress:
+1. `cargo check` — no Rust compilation errors
+2. `cargo test` — all Rust tests pass (currently 387)
+3. `cargo build --release` — release binary builds
+4. `lux test` on every package (path, frontmatter, xml, rss, markdown) — all 286 package tests pass
+5. `lux check` on every package — type checking + lint passes
+
+If `validate.sh` is not available or you need to run manually:
+```bash
+nix develop --command cargo check       # No Rust errors
+nix develop --command cargo test        # All Rust tests pass
+nix develop --command cargo build --release  # Build release binary
+cd ../packages/path && ../../lang/target/release/lux test        # Package tests
+cd ../packages/frontmatter && ../../lang/target/release/lux test
+cd ../packages/xml && ../../lang/target/release/lux test
+cd ../packages/rss && ../../lang/target/release/lux test
+cd ../packages/markdown && ../../lang/target/release/lux test
+```
+
+**Do NOT commit if any check fails.** Fix the issue first.
+
 ### Commit after every piece of work
-**After completing each logical unit of work, commit immediately.** Do not let changes accumulate uncommitted across multiple features. Each commit should be a single logical change (one feature, one bugfix, etc.). Use `--no-gpg-sign` flag for all commits.
+**After completing each logical unit of work, commit immediately.** This is NOT optional — every fix, feature, or change MUST be committed right away. Do not let changes accumulate uncommitted across multiple features. Each commit should be a single logical change (one feature, one bugfix, etc.). Use `--no-gpg-sign` flag for all commits.
+
+**Commit workflow:**
+1. Make the change
+2. Run `./scripts/validate.sh` (all 13 checks must pass)
+3. `git add` the relevant files
+4. `git commit --no-gpg-sign -m "type: description"` (use conventional commits: fix/feat/chore/docs)
+5. Move on to the next task
+
+**Never skip committing.** If you fixed a bug, commit it. If you added a feature, commit it. If you updated docs, commit it. Do not batch unrelated changes into one commit.
 
 **IMPORTANT: Always verify Lux code you write:**
 - Run with interpreter: `./target/release/lux file.lux`
@@ -109,7 +137,7 @@ When working on any major task that involves writing Lux code, **document every
 ## Code Quality
 
 - Fix all compiler warnings before committing
-- Ensure all tests pass (currently 381 tests)
+- Ensure all tests pass (currently 387 tests)
 - Add new tests when adding features
 - Keep examples and documentation in sync
 

Cargo.lock

@@ -770,7 +770,7 @@ dependencies = [
 
 [[package]]
 name = "lux"
-version = "0.1.0"
+version = "0.1.2"
 dependencies = [
  "lsp-server",
  "lsp-types",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "lux"
-version = "0.1.0"
+version = "0.1.3"
 edition = "2021"
 description = "A functional programming language with first-class effects, schema evolution, and behavioral types"
 license = "MIT"

flake.nix

@@ -44,7 +44,7 @@
             printf "\n"
             printf "  \033[1;35m╦  ╦ ╦╦ ╦\033[0m\n"
             printf "  \033[1;35m║  ║ ║╔╣\033[0m\n"
-            printf "  \033[1;35m╩═╝╚═╝╩ ╩\033[0m  v0.1.0\n"
+            printf "  \033[1;35m╩═╝╚═╝╩ ╩\033[0m  v0.1.3\n"
             printf "\n"
             printf "  Functional language with first-class effects\n"
             printf "\n"
@@ -62,7 +62,7 @@
 
         packages.default = pkgs.rustPlatform.buildRustPackage {
           pname = "lux";
-          version = "0.1.0";
+          version = "0.1.3";
           src = ./.;
           cargoLock.lockFile = ./Cargo.lock;
 
@@ -79,7 +79,7 @@
           };
         in muslPkgs.rustPlatform.buildRustPackage {
           pname = "lux";
-          version = "0.1.0";
+          version = "0.1.3";
           src = ./.;
           cargoLock.lockFile = ./Cargo.lock;
 

scripts/release.sh

@@ -5,12 +5,20 @@ set -euo pipefail
 # Builds a static binary, generates changelog, and creates a Gitea release.
 #
 # Usage:
-#   ./scripts/release.sh [version]
+#   ./scripts/release.sh              # auto-bump patch (0.2.0 → 0.2.1)
+#   ./scripts/release.sh patch        # same as above
+#   ./scripts/release.sh minor        # bump minor (0.2.0 → 0.3.0)
+#   ./scripts/release.sh major        # bump major (0.2.0 → 1.0.0)
+#   ./scripts/release.sh v1.2.3       # explicit version
 #
 # Environment:
 #   GITEA_TOKEN - API token for git.qrty.ink (prompted if not set)
 #   GITEA_URL   - Gitea instance URL (default: https://git.qrty.ink)
 
+# cd to repo root (directory containing this script's parent)
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+cd "$SCRIPT_DIR/.."
+
 GITEA_URL="${GITEA_URL:-https://git.qrty.ink}"
 REPO_OWNER="blu"
 REPO_NAME="lux"
@@ -30,14 +38,33 @@ warn()  { printf "${YELLOW}!!${NC} %s\n" "$1"; }
 err()   { printf "${RED}error:${NC} %s\n" "$1" >&2; exit 1; }
 
 # --- Determine version ---
-VERSION="${1:-}"
+CURRENT=$(grep '^version' Cargo.toml | head -1 | sed 's/.*"\(.*\)".*/\1/')
-if [ -z "$VERSION" ]; then
+BUMP="${1:-patch}"
-    VERSION=$(grep '^version' Cargo.toml | head -1 | sed 's/.*"\(.*\)".*/\1/')
+
-    info "Version from Cargo.toml: v$VERSION"
+bump_version() {
-fi
+    local ver="$1" part="$2"
-# Ensure v prefix
+    IFS='.' read -r major minor patch <<< "$ver"
-[[ "$VERSION" == v* ]] || VERSION="v$VERSION"
+    case "$part" in
-TAG="$VERSION"
+        major) echo "$((major + 1)).0.0" ;;
+        minor) echo "$major.$((minor + 1)).0" ;;
+        patch) echo "$major.$minor.$((patch + 1))" ;;
+        *)     echo "$part" ;;  # treat as explicit version
+    esac
+}
+
+case "$BUMP" in
+    major|minor|patch)
+        VERSION=$(bump_version "$CURRENT" "$BUMP")
+        info "Bumping $BUMP: $CURRENT → $VERSION"
+        ;;
+    *)
+        # Explicit version — strip v prefix if present
+        VERSION="${BUMP#v}"
+        info "Explicit version: $VERSION"
+        ;;
+esac
+
+TAG="v$VERSION"
 
 # --- Check for clean working tree ---
 if [ -n "$(git status --porcelain)" ]; then
@@ -50,7 +77,18 @@ fi
 
 # --- Check if tag already exists ---
 if git rev-parse "$TAG" >/dev/null 2>&1; then
-    err "Tag $TAG already exists. Bump version in Cargo.toml or choose a different version."
+    err "Tag $TAG already exists. Choose a different version."
+fi
+
+# --- Update version in source files ---
+if [ "$VERSION" != "$CURRENT" ]; then
+    info "Updating version in Cargo.toml and flake.nix..."
+    sed -i "0,/^version = \"$CURRENT\"/s//version = \"$VERSION\"/" Cargo.toml
+    sed -i "s/version = \"$CURRENT\";/version = \"$VERSION\";/g" flake.nix
+    sed -i "s/v$CURRENT/v$VERSION/g" flake.nix
+    git add Cargo.toml flake.nix
+    git commit --no-gpg-sign -m "chore: bump version to $VERSION"
+    ok "Version updated and committed"
 fi
 
 # --- Generate changelog ---
@@ -64,7 +102,7 @@ else
     info "First release — summarizing recent commits:"
 fi
 
-CHANGELOG=$(git log "$RANGE" --pretty=format:"- %s" --no-merges 2>/dev/null | head -50)
+CHANGELOG=$(git log "$RANGE" --pretty=format:"- %s" --no-merges 2>/dev/null | head -50 || true)
 if [ -z "$CHANGELOG" ]; then
     CHANGELOG="- Initial release"
 fi

scripts/validate.sh

@@ -0,0 +1,73 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Lux Full Validation Script
+# Runs all checks: Rust tests, package tests, type checking, formatting, linting.
+# Run after every committable change to ensure no regressions.
+
+# cd to repo root (directory containing this script's parent)
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+cd "$SCRIPT_DIR/.."
+
+LUX="$(pwd)/target/release/lux"
+PACKAGES_DIR="$(pwd)/../packages"
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+CYAN='\033[0;36m'
+BOLD='\033[1m'
+NC='\033[0m'
+
+FAILED=0
+TOTAL=0
+
+step() {
+    TOTAL=$((TOTAL + 1))
+    printf "${CYAN}[%d]${NC} %s... " "$TOTAL" "$1"
+}
+
+ok() { printf "${GREEN}ok${NC} %s\n" "${1:-}"; }
+fail() { printf "${RED}FAIL${NC} %s\n" "${1:-}"; FAILED=$((FAILED + 1)); }
+
+# --- Rust checks ---
+step "cargo check"
+if nix develop --command cargo check 2>&1 | grep -q "Finished"; then ok; else fail; fi
+
+step "cargo test"
+OUTPUT=$(nix develop --command cargo test 2>&1 || true)
+RESULT=$(echo "$OUTPUT" | grep "test result:" || echo "no result")
+if echo "$RESULT" | grep -q "0 failed"; then ok "$RESULT"; else fail "$RESULT"; fi
+
+# --- Build release binary ---
+step "cargo build --release"
+if nix develop --command cargo build --release 2>&1 | grep -q "Finished"; then ok; else fail; fi
+
+# --- Package tests ---
+for pkg in path frontmatter xml rss markdown; do
+    PKG_DIR="$PACKAGES_DIR/$pkg"
+    if [ -d "$PKG_DIR" ]; then
+        step "lux test ($pkg)"
+        OUTPUT=$(cd "$PKG_DIR" && "$LUX" test 2>&1 || true)
+        RESULT=$(echo "$OUTPUT" | grep "passed" | tail -1 || echo "no result")
+        if echo "$RESULT" | grep -q "passed"; then ok "$RESULT"; else fail "$RESULT"; fi
+    fi
+done
+
+# --- Lux check on packages ---
+for pkg in path frontmatter xml rss markdown; do
+    PKG_DIR="$PACKAGES_DIR/$pkg"
+    if [ -d "$PKG_DIR" ]; then
+        step "lux check ($pkg)"
+        OUTPUT=$(cd "$PKG_DIR" && "$LUX" check 2>&1 || true)
+        RESULT=$(echo "$OUTPUT" | grep "passed" | tail -1 || echo "no result")
+        if echo "$RESULT" | grep -q "passed"; then ok; else fail "$RESULT"; fi
+    fi
+done
+
+# --- Summary ---
+printf "\n${BOLD}═══ Validation Summary ═══${NC}\n"
+if [ $FAILED -eq 0 ]; then
+    printf "${GREEN}All %d checks passed.${NC}\n" "$TOTAL"
+else
+    printf "${RED}%d/%d checks failed.${NC}\n" "$FAILED" "$TOTAL"
+    exit 1
+fi

src/ast.rs

@@ -541,7 +541,9 @@ pub enum Expr {
         span: Span,
     },
     /// Record literal: { name: "Alice", age: 30 }
+    /// With optional spread: { ...base, name: "Bob" }
     Record {
+        spread: Option<Box<Expr>>,
         fields: Vec<(Ident, Expr)>,
         span: Span,
     },
@@ -622,6 +624,7 @@ pub enum BinaryOp {
     Or,
     // Other
     Pipe,   // |>
+    Concat, // ++
 }
 
 impl fmt::Display for BinaryOp {
@@ -641,6 +644,7 @@ impl fmt::Display for BinaryOp {
             BinaryOp::And => write!(f, "&&"),
             BinaryOp::Or => write!(f, "||"),
             BinaryOp::Pipe => write!(f, "|>"),
+            BinaryOp::Concat => write!(f, "++"),
         }
     }
 }

src/codegen/c_backend.rs

@@ -730,10 +730,10 @@ impl CBackend {
                 }
 
                 // Check for string concatenation - use lux_string_concat instead of +
-                if matches!(op, BinaryOp::Add) {
+                if matches!(op, BinaryOp::Add | BinaryOp::Concat) {
                     let left_is_string = self.infer_expr_type(left).as_deref() == Some("LuxString");
                     let right_is_string = self.infer_expr_type(right).as_deref() == Some("LuxString");
-                    if left_is_string || right_is_string {
+                    if left_is_string || right_is_string || matches!(op, BinaryOp::Concat) {
                         return Ok(format!("lux_string_concat({}, {})", l, r));
                     }
                 }
@@ -858,6 +858,7 @@ impl CBackend {
         self.writeln("#include <stdio.h>");
         self.writeln("#include <stdlib.h>");
         self.writeln("#include <string.h>");
+        self.writeln("#include <math.h>");
         self.writeln("");
         self.writeln("// === Lux Runtime Types ===");
         self.writeln("");
@@ -2839,8 +2840,18 @@ impl CBackend {
                     }
                 }
 
+                // String concatenation for ++ and +
+                if matches!(op, BinaryOp::Add | BinaryOp::Concat) {
+                    let left_is_string = self.infer_expr_type(left).as_deref() == Some("LuxString");
+                    let right_is_string = self.infer_expr_type(right).as_deref() == Some("LuxString");
+                    if left_is_string || right_is_string || matches!(op, BinaryOp::Concat) {
+                        return Ok(format!("lux_string_concat({}, {})", l, r));
+                    }
+                }
+
                 let op_str = match op {
                     BinaryOp::Add => "+",
+                    BinaryOp::Concat => unreachable!("handled above"),
                     BinaryOp::Sub => "-",
                     BinaryOp::Mul => "*",
                     BinaryOp::Div => "/",
@@ -3019,6 +3030,10 @@ impl CBackend {
                             self.register_rc_var(&temp, "LuxString");
                             return Ok(temp);
                         }
+                        // Math module
+                        if module_name.name == "Math" {
+                            return self.emit_math_operation(&field.name, args);
+                        }
                         // Check for user-defined module function
                         let key = (module_name.name.clone(), field.name.clone());
                         if let Some(c_name) = self.module_functions.get(&key).cloned() {
@@ -3382,6 +3397,11 @@ impl CBackend {
                     }
                 }
 
+                // Math module (treated as effect by parser but handled as direct C calls)
+                if effect.name == "Math" {
+                    return self.emit_math_operation(&operation.name, args);
+                }
+
                 // Built-in Console effect
                 if effect.name == "Console" {
                     if operation.name == "print" {
@@ -3844,13 +3864,35 @@ impl CBackend {
                 }
             }
 
-            Expr::Record { fields, .. } => {
+            Expr::Record {
-                let field_strs: Result<Vec<_>, _> = fields.iter().map(|(name, val)| {
+                spread, fields, ..
+            } => {
+                if let Some(spread_expr) = spread {
+                    // Evaluate spread source, then override fields
+                    let base = self.emit_expr(spread_expr)?;
+                    if fields.is_empty() {
+                        Ok(base)
+                    } else {
+                        // Copy spread into a temp, then override fields
+                        let temp = format!("_spread_{}", self.fresh_name());
+                        self.writeln(&format!("__auto_type {} = {};", temp, base));
+                        for (name, val) in fields {
+                            let v = self.emit_expr(val)?;
+                            self.writeln(&format!("{}.{} = {};", temp, name.name, v));
+                        }
+                        Ok(temp)
+                    }
+                } else {
+                    let field_strs: Result<Vec<_>, _> = fields
+                        .iter()
+                        .map(|(name, val)| {
                             let v = self.emit_expr(val)?;
                             Ok(format!(".{} = {}", name.name, v))
-                }).collect();
+                        })
+                        .collect();
                     Ok(format!("{{ {} }}", field_strs?.join(", ")))
                 }
+            }
 
             Expr::Field { object, field, .. } => {
                 let obj = self.emit_expr(object)?;
@@ -3919,6 +3961,64 @@ impl CBackend {
         }
     }
 
+    /// Emit code for Math module operations (Math.sin, Math.cos, etc.)
+    fn emit_math_operation(&mut self, op: &str, args: &[Expr]) -> Result<String, CGenError> {
+        match op {
+            "abs" => {
+                let x = self.emit_expr(&args[0])?;
+                Ok(format!("fabs({})", x))
+            }
+            "min" => {
+                let a = self.emit_expr(&args[0])?;
+                let b = self.emit_expr(&args[1])?;
+                Ok(format!("fmin({}, {})", a, b))
+            }
+            "max" => {
+                let a = self.emit_expr(&args[0])?;
+                let b = self.emit_expr(&args[1])?;
+                Ok(format!("fmax({}, {})", a, b))
+            }
+            "sqrt" => {
+                let x = self.emit_expr(&args[0])?;
+                Ok(format!("sqrt({})", x))
+            }
+            "pow" => {
+                let base = self.emit_expr(&args[0])?;
+                let exp = self.emit_expr(&args[1])?;
+                Ok(format!("pow({}, {})", base, exp))
+            }
+            "floor" => {
+                let x = self.emit_expr(&args[0])?;
+                Ok(format!("(int64_t)floor({})", x))
+            }
+            "ceil" => {
+                let x = self.emit_expr(&args[0])?;
+                Ok(format!("(int64_t)ceil({})", x))
+            }
+            "round" => {
+                let x = self.emit_expr(&args[0])?;
+                Ok(format!("(int64_t)round({})", x))
+            }
+            "sin" => {
+                let x = self.emit_expr(&args[0])?;
+                Ok(format!("sin({})", x))
+            }
+            "cos" => {
+                let x = self.emit_expr(&args[0])?;
+                Ok(format!("cos({})", x))
+            }
+            "atan2" => {
+                let y = self.emit_expr(&args[0])?;
+                let x = self.emit_expr(&args[1])?;
+                Ok(format!("atan2({}, {})", y, x))
+            }
+            _ => Err(CGenError {
+                message: format!("Math.{} not supported in C backend", op),
+                span: None,
+            }),
+        }
+    }
+
     /// Emit code for List module operations (List.map, List.filter, etc.)
     fn emit_list_operation(&mut self, op: &str, args: &[Expr]) -> Result<String, CGenError> {
         match op {
@@ -5821,7 +5921,10 @@ impl CBackend {
                 }
                 self.collect_free_vars(body, &inner_bound, free);
             }
-            Expr::Record { fields, .. } => {
+            Expr::Record { spread, fields, .. } => {
+                if let Some(spread_expr) = spread {
+                    self.collect_free_vars(spread_expr, bound, free);
+                }
                 for (_, val) in fields {
                     self.collect_free_vars(val, bound, free);
                 }

src/codegen/js_backend.rs

@@ -909,13 +909,16 @@ impl JsBackend {
         let val = self.emit_expr(&let_decl.value)?;
         let var_name = &let_decl.name.name;
 
-        // Check if this is a run expression (often results in undefined)
+        if var_name == "_" {
-        // We still want to execute it for its side effects
+            // Wildcard binding: just execute for side effects
+            self.writeln(&format!("{};", val));
+        } else {
             self.writeln(&format!("const {} = {};", var_name, val));
 
             // Register the variable for future use
             self.var_substitutions
                 .insert(var_name.clone(), var_name.clone());
+        }
 
         Ok(())
     }
@@ -954,12 +957,17 @@ impl JsBackend {
                 let r = self.emit_expr(right)?;
 
                 // Check for string concatenation
-                if matches!(op, BinaryOp::Add) {
+                if matches!(op, BinaryOp::Add | BinaryOp::Concat) {
                     if self.is_string_expr(left) || self.is_string_expr(right) {
                         return Ok(format!("({} + {})", l, r));
                     }
                 }
 
+                // ++ on lists: use .concat()
+                if matches!(op, BinaryOp::Concat) {
+                    return Ok(format!("{}.concat({})", l, r));
+                }
+
                 let op_str = match op {
                     BinaryOp::Add => "+",
                     BinaryOp::Sub => "-",
@@ -974,6 +982,7 @@ impl JsBackend {
                     BinaryOp::Ge => ">=",
                     BinaryOp::And => "&&",
                     BinaryOp::Or => "||",
+                    BinaryOp::Concat => unreachable!("handled above"),
                     BinaryOp::Pipe => {
                         // Pipe operator: x |> f becomes f(x)
                         return Ok(format!("{}({})", r, l));
@@ -1034,6 +1043,11 @@ impl JsBackend {
                 name, value, body, ..
             } => {
                 let val = self.emit_expr(value)?;
+
+                if name.name == "_" {
+                    // Wildcard binding: just execute for side effects
+                    self.writeln(&format!("{};", val));
+                } else {
                     let var_name = format!("{}_{}", name.name, self.fresh_name());
 
                     self.writeln(&format!("const {} = {};", var_name, val));
@@ -1041,11 +1055,14 @@ impl JsBackend {
                     // Add substitution
                     self.var_substitutions
                         .insert(name.name.clone(), var_name.clone());
+                }
 
                 let body_result = self.emit_expr(body)?;
 
                 // Remove substitution
+                if name.name != "_" {
                     self.var_substitutions.remove(&name.name);
+                }
 
                 Ok(body_result)
             }
@@ -1066,6 +1083,10 @@ impl JsBackend {
                         let arg = self.emit_expr(&args[0])?;
                         return Ok(format!("String({})", arg));
                     }
+                    if ident.name == "print" {
+                        let arg = self.emit_expr(&args[0])?;
+                        return Ok(format!("console.log({})", arg));
+                    }
                 }
 
                 let arg_strs: Result<Vec<_>, _> = args.iter().map(|a| self.emit_expr(a)).collect();
@@ -1228,27 +1249,36 @@ impl JsBackend {
                         }
                         Statement::Let { name, value, .. } => {
                             let val = self.emit_expr(value)?;
-                            let var_name = format!("{}_{}", name.name, self.fresh_name());
+                            if name.name == "_" {
+                                self.writeln(&format!("{};", val));
+                            } else {
+                                let var_name =
+                                    format!("{}_{}", name.name, self.fresh_name());
                                 self.writeln(&format!("const {} = {};", var_name, val));
                                 self.var_substitutions
                                     .insert(name.name.clone(), var_name.clone());
                             }
                         }
                     }
+                }
 
                 // Emit result
                 self.emit_expr(result)
             }
 
-            Expr::Record { fields, .. } => {
+            Expr::Record {
-                let field_strs: Result<Vec<_>, _> = fields
+                spread, fields, ..
-                    .iter()
+            } => {
-                    .map(|(name, expr)| {
+                let mut parts = Vec::new();
+                if let Some(spread_expr) = spread {
+                    let spread_code = self.emit_expr(spread_expr)?;
+                    parts.push(format!("...{}", spread_code));
+                }
+                for (name, expr) in fields {
                     let val = self.emit_expr(expr)?;
-                        Ok(format!("{}: {}", name.name, val))
+                    parts.push(format!("{}: {}", name.name, val));
-                    })
+                }
-                    .collect();
+                Ok(format!("{{ {} }}", parts.join(", ")))
-                Ok(format!("{{ {} }}", field_strs?.join(", ")))
             }
 
             Expr::Tuple { elements, .. } => {
@@ -2338,7 +2368,7 @@ impl JsBackend {
                 }
             }
             Expr::BinaryOp { op, left, right, .. } => {
-                matches!(op, BinaryOp::Add)
+                matches!(op, BinaryOp::Add | BinaryOp::Concat)
                     && (self.is_string_expr(left) || self.is_string_expr(right))
             }
             _ => false,

src/formatter.rs

@@ -688,15 +688,17 @@ impl Formatter {
                         .join(", ")
                 )
             }
-            Expr::Record { fields, .. } => {
+            Expr::Record {
-                format!(
+                spread, fields, ..
-                    "{{ {} }}",
+            } => {
-                    fields
+                let mut parts = Vec::new();
-                        .iter()
+                if let Some(spread_expr) = spread {
-                        .map(|(name, val)| format!("{}: {}", name.name, self.format_expr(val)))
+                    parts.push(format!("...{}", self.format_expr(spread_expr)));
-                        .collect::<Vec<_>>()
+                }
-                        .join(", ")
+                for (name, val) in fields {
-                )
+                    parts.push(format!("{}: {}", name.name, self.format_expr(val)));
+                }
+                format!("{{ {} }}", parts.join(", "))
             }
             Expr::EffectOp { effect, operation, args, .. } => {
                 format!(
@@ -753,6 +755,7 @@ impl Formatter {
             BinaryOp::Ge => ">=",
             BinaryOp::And => "&&",
             BinaryOp::Or => "||",
+            BinaryOp::Concat => "++",
             BinaryOp::Pipe => "|>",
         }
     }

src/interpreter.rs

@@ -74,6 +74,9 @@ pub enum BuiltinFn {
     MathFloor,
     MathCeil,
     MathRound,
+    MathSin,
+    MathCos,
+    MathAtan2,
 
     // Additional List operations
     ListIsEmpty,
@@ -1072,6 +1075,9 @@ impl Interpreter {
             ("floor".to_string(), Value::Builtin(BuiltinFn::MathFloor)),
             ("ceil".to_string(), Value::Builtin(BuiltinFn::MathCeil)),
             ("round".to_string(), Value::Builtin(BuiltinFn::MathRound)),
+            ("sin".to_string(), Value::Builtin(BuiltinFn::MathSin)),
+            ("cos".to_string(), Value::Builtin(BuiltinFn::MathCos)),
+            ("atan2".to_string(), Value::Builtin(BuiltinFn::MathAtan2)),
         ]));
         env.define("Math", math_module);
 
@@ -1115,11 +1121,50 @@ impl Interpreter {
     /// Execute a program
     pub fn run(&mut self, program: &Program) -> Result<Value, RuntimeError> {
         let mut last_value = Value::Unit;
+        let mut has_main_let = false;
 
         for decl in &program.declarations {
+            // Track if there's a top-level `let main = ...`
+            if let Declaration::Let(let_decl) = decl {
+                if let_decl.name.name == "main" {
+                    has_main_let = true;
+                }
+            }
             last_value = self.eval_declaration(decl)?;
         }
 
+        // Auto-invoke main if it was defined as a let binding with a function value
+        if has_main_let {
+            if let Some(main_val) = self.global_env.get("main") {
+                if let Value::Function(ref closure) = main_val {
+                    if closure.params.is_empty() {
+                        let span = Span { start: 0, end: 0 };
+                        let mut result = self.eval_call(main_val.clone(), vec![], span)?;
+                        // Trampoline loop
+                        loop {
+                            match result {
+                                EvalResult::Value(v) => {
+                                    last_value = v;
+                                    break;
+                                }
+                                EvalResult::Effect(req) => {
+                                    last_value = self.handle_effect(req)?;
+                                    break;
+                                }
+                                EvalResult::TailCall { func, args, span } => {
+                                    result = self.eval_call(func, args, span)?;
+                                }
+                                EvalResult::Resume(v) => {
+                                    last_value = v;
+                                    break;
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
         Ok(last_value)
     }
 
@@ -1525,8 +1570,28 @@ impl Interpreter {
                 self.eval_expr_tail(result, &block_env, tail)
             }
 
-            Expr::Record { fields, .. } => {
+            Expr::Record {
+                spread, fields, ..
+            } => {
                 let mut record = HashMap::new();
+
+                // If there's a spread, evaluate it and start with its fields
+                if let Some(spread_expr) = spread {
+                    let spread_val = self.eval_expr(spread_expr, env)?;
+                    if let Value::Record(spread_fields) = spread_val {
+                        record = spread_fields;
+                    } else {
+                        return Err(RuntimeError {
+                            message: format!(
+                                "Spread expression must evaluate to a record, got {}",
+                                spread_val.type_name()
+                            ),
+                            span: Some(expr.span()),
+                        });
+                    }
+                }
+
+                // Override with explicit fields
                 for (name, expr) in fields {
                     let val = self.eval_expr(expr, env)?;
                     record.insert(name.name.clone(), val);
@@ -1599,6 +1664,18 @@ impl Interpreter {
                     span: Some(span),
                 }),
             },
+            BinaryOp::Concat => match (left, right) {
+                (Value::String(a), Value::String(b)) => Ok(Value::String(a + &b)),
+                (Value::List(a), Value::List(b)) => {
+                    let mut result = a;
+                    result.extend(b);
+                    Ok(Value::List(result))
+                }
+                (l, r) => Err(RuntimeError {
+                    message: format!("Cannot concatenate {} and {}", l.type_name(), r.type_name()),
+                    span: Some(span),
+                }),
+            },
             BinaryOp::Sub => match (left, right) {
                 (Value::Int(a), Value::Int(b)) => Ok(Value::Int(a - b)),
                 (Value::Float(a), Value::Float(b)) => Ok(Value::Float(a - b)),
@@ -2463,6 +2540,45 @@ impl Interpreter {
                 }
             }
 
+            BuiltinFn::MathSin => {
+                if args.len() != 1 {
+                    return Err(err("Math.sin requires 1 argument"));
+                }
+                match &args[0] {
+                    Value::Float(n) => Ok(EvalResult::Value(Value::Float(n.sin()))),
+                    Value::Int(n) => Ok(EvalResult::Value(Value::Float((*n as f64).sin()))),
+                    v => Err(err(&format!("Math.sin expects number, got {}", v.type_name()))),
+                }
+            }
+
+            BuiltinFn::MathCos => {
+                if args.len() != 1 {
+                    return Err(err("Math.cos requires 1 argument"));
+                }
+                match &args[0] {
+                    Value::Float(n) => Ok(EvalResult::Value(Value::Float(n.cos()))),
+                    Value::Int(n) => Ok(EvalResult::Value(Value::Float((*n as f64).cos()))),
+                    v => Err(err(&format!("Math.cos expects number, got {}", v.type_name()))),
+                }
+            }
+
+            BuiltinFn::MathAtan2 => {
+                if args.len() != 2 {
+                    return Err(err("Math.atan2 requires 2 arguments: y, x"));
+                }
+                let y = match &args[0] {
+                    Value::Float(n) => *n,
+                    Value::Int(n) => *n as f64,
+                    v => return Err(err(&format!("Math.atan2 expects number, got {}", v.type_name()))),
+                };
+                let x = match &args[1] {
+                    Value::Float(n) => *n,
+                    Value::Int(n) => *n as f64,
+                    v => return Err(err(&format!("Math.atan2 expects number, got {}", v.type_name()))),
+                };
+                Ok(EvalResult::Value(Value::Float(y.atan2(x))))
+            }
+
             // Additional List operations
             BuiltinFn::ListIsEmpty => {
                 let list = Self::expect_arg_1::<Vec<Value>>(&args, "List.isEmpty", span)?;
@@ -5044,6 +5160,7 @@ mod tests {
         // Create a simple migration that adds a field
         // Migration: old.name -> { name: old.name, email: "unknown" }
         let migration_body = Expr::Record {
+            spread: None,
             fields: vec![
                 (
                     Ident::new("name", Span::default()),

src/lexer.rs

@@ -70,6 +70,7 @@ pub enum TokenKind {
 
     // Operators
     Plus,       // +
+    PlusPlus,   // ++
     Minus,      // -
     Star,       // *
     Slash,      // /
@@ -89,6 +90,7 @@ pub enum TokenKind {
     Arrow,      // =>
     ThinArrow,  // ->
     Dot,        // .
+    DotDotDot,  // ...
     Colon,      // :
     ColonColon, // ::
     Comma,      // ,
@@ -160,6 +162,7 @@ impl fmt::Display for TokenKind {
             TokenKind::True => write!(f, "true"),
             TokenKind::False => write!(f, "false"),
             TokenKind::Plus => write!(f, "+"),
+            TokenKind::PlusPlus => write!(f, "++"),
             TokenKind::Minus => write!(f, "-"),
             TokenKind::Star => write!(f, "*"),
             TokenKind::Slash => write!(f, "/"),
@@ -179,6 +182,7 @@ impl fmt::Display for TokenKind {
             TokenKind::Arrow => write!(f, "=>"),
             TokenKind::ThinArrow => write!(f, "->"),
             TokenKind::Dot => write!(f, "."),
+            TokenKind::DotDotDot => write!(f, "..."),
             TokenKind::Colon => write!(f, ":"),
             TokenKind::ColonColon => write!(f, "::"),
             TokenKind::Comma => write!(f, ","),
@@ -268,7 +272,14 @@ impl<'a> Lexer<'a> {
 
         let kind = match c {
             // Single-character tokens
-            '+' => TokenKind::Plus,
+            '+' => {
+                if self.peek() == Some('+') {
+                    self.advance();
+                    TokenKind::PlusPlus
+                } else {
+                    TokenKind::Plus
+                }
+            }
             '*' => TokenKind::Star,
             '%' => TokenKind::Percent,
             '(' => TokenKind::LParen,
@@ -364,7 +375,22 @@ impl<'a> Lexer<'a> {
                     TokenKind::Pipe
                 }
             }
-            '.' => TokenKind::Dot,
+            '.' => {
+                if self.peek() == Some('.') {
+                    // Check for ... (need to peek past second dot)
+                    // We look at source directly since we can only peek one ahead
+                    let next_next = self.source[self.pos..].chars().nth(1);
+                    if next_next == Some('.') {
+                        self.advance(); // consume second '.'
+                        self.advance(); // consume third '.'
+                        TokenKind::DotDotDot
+                    } else {
+                        TokenKind::Dot
+                    }
+                } else {
+                    TokenKind::Dot
+                }
+            }
             ':' => {
                 if self.peek() == Some(':') {
                     self.advance();

src/linter.rs

@@ -513,7 +513,10 @@ impl Linter {
             Expr::Field { object, .. } | Expr::TupleIndex { object, .. } => {
                 self.collect_refs_expr(object);
             }
-            Expr::Record { fields, .. } => {
+            Expr::Record { spread, fields, .. } => {
+                if let Some(spread_expr) = spread {
+                    self.collect_refs_expr(spread_expr);
+                }
                 for (_, val) in fields {
                     self.collect_refs_expr(val);
                 }

src/lsp.rs

@@ -1571,7 +1571,10 @@ fn collect_call_site_hints(
                 collect_call_site_hints(source, e, param_names, hints);
             }
         }
-        Expr::Record { fields, .. } => {
+        Expr::Record { spread, fields, .. } => {
+            if let Some(spread_expr) = spread {
+                collect_call_site_hints(source, spread_expr, param_names, hints);
+            }
             for (_, e) in fields {
                 collect_call_site_hints(source, e, param_names, hints);
             }

src/main.rs

@@ -37,7 +37,7 @@ use std::borrow::Cow;
 use std::collections::HashSet;
 use typechecker::TypeChecker;
 
-const VERSION: &str = "0.1.0";
+const VERSION: &str = env!("CARGO_PKG_VERSION");
 
 const HELP: &str = r#"
 Lux - A functional language with first-class effects
@@ -902,6 +902,7 @@ fn compile_to_c(path: &str, output_path: Option<&str>, run_after: bool, emit_c:
         .args(["-O2", "-o"])
         .arg(&output_bin)
         .arg(&temp_c)
+        .arg("-lm")
         .output();
 
     match compile_result {

src/parser.rs

@@ -1558,6 +1558,7 @@ impl Parser {
         loop {
             let op = match self.peek_kind() {
                 TokenKind::Plus => BinaryOp::Add,
+                TokenKind::PlusPlus => BinaryOp::Concat,
                 TokenKind::Minus => BinaryOp::Sub,
                 _ => break,
             };
@@ -2207,6 +2208,11 @@ impl Parser {
             }));
         }
 
+        // Check for record spread: { ...expr, field: val }
+        if matches!(self.peek_kind(), TokenKind::DotDotDot) {
+            return self.parse_record_expr_rest(start);
+        }
+
         // Check if it's a record (ident: expr) or block
         if matches!(self.peek_kind(), TokenKind::Ident(_)) {
             let lookahead = self.tokens.get(self.pos + 1).map(|t| &t.kind);
@@ -2221,6 +2227,20 @@ impl Parser {
 
     fn parse_record_expr_rest(&mut self, start: Span) -> Result<Expr, ParseError> {
         let mut fields = Vec::new();
+        let mut spread = None;
+
+        // Check for spread: { ...expr, ... }
+        if self.check(TokenKind::DotDotDot) {
+            self.advance(); // consume ...
+            let spread_expr = self.parse_expr()?;
+            spread = Some(Box::new(spread_expr));
+
+            self.skip_newlines();
+            if self.check(TokenKind::Comma) {
+                self.advance();
+            }
+            self.skip_newlines();
+        }
 
         while !self.check(TokenKind::RBrace) {
             let name = self.parse_ident()?;
@@ -2237,7 +2257,11 @@ impl Parser {
 
         self.expect(TokenKind::RBrace)?;
         let span = start.merge(self.previous_span());
-        Ok(Expr::Record { fields, span })
+        Ok(Expr::Record {
+            spread,
+            fields,
+            span,
+        })
     }
 
     fn parse_block_rest(&mut self, start: Span) -> Result<Expr, ParseError> {

src/symbol_table.rs

@@ -527,7 +527,10 @@ impl SymbolTable {
                     self.visit_expr(e, scope_idx);
                 }
             }
-            Expr::Record { fields, .. } => {
+            Expr::Record { spread, fields, .. } => {
+                if let Some(spread_expr) = spread {
+                    self.visit_expr(spread_expr, scope_idx);
+                }
                 for (_, e) in fields {
                     self.visit_expr(e, scope_idx);
                 }

src/typechecker.rs

@@ -339,7 +339,10 @@ fn references_params(expr: &Expr, params: &[&str]) -> bool {
         Expr::Lambda { body, .. } => references_params(body, params),
         Expr::Tuple { elements, .. } => elements.iter().any(|e| references_params(e, params)),
         Expr::List { elements, .. } => elements.iter().any(|e| references_params(e, params)),
-        Expr::Record { fields, .. } => fields.iter().any(|(_, e)| references_params(e, params)),
+        Expr::Record { spread, fields, .. } => {
+            spread.as_ref().is_some_and(|s| references_params(s, params))
+                || fields.iter().any(|(_, e)| references_params(e, params))
+        }
         Expr::Match { scrutinee, arms, .. } => {
             references_params(scrutinee, params)
                 || arms.iter().any(|a| references_params(&a.body, params))
@@ -516,8 +519,9 @@ fn has_recursive_calls(func_name: &str, body: &Expr) -> bool {
         Expr::Tuple { elements, .. } | Expr::List { elements, .. } => {
             elements.iter().any(|e| has_recursive_calls(func_name, e))
         }
-        Expr::Record { fields, .. } => {
+        Expr::Record { spread, fields, .. } => {
-            fields.iter().any(|(_, e)| has_recursive_calls(func_name, e))
+            spread.as_ref().is_some_and(|s| has_recursive_calls(func_name, s))
+                || fields.iter().any(|(_, e)| has_recursive_calls(func_name, e))
         }
         Expr::Field { object, .. } | Expr::TupleIndex { object, .. } => has_recursive_calls(func_name, object),
         Expr::Let { value, body, .. } => {
@@ -672,6 +676,7 @@ fn generate_auto_migration_expr(
 
     // Build the record expression
     Some(Expr::Record {
+        spread: None,
         fields: field_exprs,
         span,
     })
@@ -1536,7 +1541,7 @@ impl TypeChecker {
         // Use the declared type if present, otherwise use inferred
         let final_type = if let Some(ref type_expr) = let_decl.typ {
             let declared = self.resolve_type(type_expr);
-            if let Err(e) = unify(&inferred, &declared) {
+            if let Err(e) = unify_with_env(&inferred, &declared, &self.env) {
                 self.errors.push(TypeError {
                     message: format!(
                         "Variable '{}' has type {}, but declared type is {}: {}",
@@ -1744,7 +1749,11 @@ impl TypeChecker {
                 span,
             } => self.infer_block(statements, result, *span),
 
-            Expr::Record { fields, span } => self.infer_record(fields, *span),
+            Expr::Record {
+                spread,
+                fields,
+                span,
+            } => self.infer_record(spread.as_deref(), fields, *span),
 
             Expr::Tuple { elements, span } => self.infer_tuple(elements, *span),
 
@@ -1783,7 +1792,7 @@ impl TypeChecker {
         match op {
             BinaryOp::Add => {
                 // Add supports both numeric types and string concatenation
-                if let Err(e) = unify(&left_type, &right_type) {
+                if let Err(e) = unify_with_env(&left_type, &right_type, &self.env) {
                     self.errors.push(TypeError {
                         message: format!("Operands of '{}' must have same type: {}", op, e),
                         span,
@@ -1804,9 +1813,32 @@ impl TypeChecker {
                 }
             }
 
+            BinaryOp::Concat => {
+                // Concat (++) supports strings and lists
+                if let Err(e) = unify_with_env(&left_type, &right_type, &self.env) {
+                    self.errors.push(TypeError {
+                        message: format!("Operands of '++' must have same type: {}", e),
+                        span,
+                    });
+                }
+                match &left_type {
+                    Type::String | Type::List(_) | Type::Var(_) => left_type,
+                    _ => {
+                        self.errors.push(TypeError {
+                            message: format!(
+                                "Operator '++' requires String or List operands, got {}",
+                                left_type
+                            ),
+                            span,
+                        });
+                        Type::Error
+                    }
+                }
+            }
+
             BinaryOp::Sub | BinaryOp::Mul | BinaryOp::Div | BinaryOp::Mod => {
                 // Arithmetic: both operands must be same numeric type
-                if let Err(e) = unify(&left_type, &right_type) {
+                if let Err(e) = unify_with_env(&left_type, &right_type, &self.env) {
                     self.errors.push(TypeError {
                         message: format!("Operands of '{}' must have same type: {}", op, e),
                         span,
@@ -1830,7 +1862,7 @@ impl TypeChecker {
 
             BinaryOp::Eq | BinaryOp::Ne => {
                 // Equality: operands must have same type
-                if let Err(e) = unify(&left_type, &right_type) {
+                if let Err(e) = unify_with_env(&left_type, &right_type, &self.env) {
                     self.errors.push(TypeError {
                         message: format!("Operands of '{}' must have same type: {}", op, e),
                         span,
@@ -1841,7 +1873,7 @@ impl TypeChecker {
 
             BinaryOp::Lt | BinaryOp::Le | BinaryOp::Gt | BinaryOp::Ge => {
                 // Comparison: operands must be same orderable type
-                if let Err(e) = unify(&left_type, &right_type) {
+                if let Err(e) = unify_with_env(&left_type, &right_type, &self.env) {
                     self.errors.push(TypeError {
                         message: format!("Operands of '{}' must have same type: {}", op, e),
                         span,
@@ -1852,13 +1884,13 @@ impl TypeChecker {
 
             BinaryOp::And | BinaryOp::Or => {
                 // Logical: both must be Bool
-                if let Err(e) = unify(&left_type, &Type::Bool) {
+                if let Err(e) = unify_with_env(&left_type, &Type::Bool, &self.env) {
                     self.errors.push(TypeError {
                         message: format!("Left operand of '{}' must be Bool: {}", op, e),
                         span: left.span(),
                     });
                 }
-                if let Err(e) = unify(&right_type, &Type::Bool) {
+                if let Err(e) = unify_with_env(&right_type, &Type::Bool, &self.env) {
                     self.errors.push(TypeError {
                         message: format!("Right operand of '{}' must be Bool: {}", op, e),
                         span: right.span(),
@@ -1872,7 +1904,7 @@ impl TypeChecker {
                 // right must be a function that accepts left's type
                 let result_type = Type::var();
                 let expected_fn = Type::function(vec![left_type.clone()], result_type.clone());
-                if let Err(e) = unify(&right_type, &expected_fn) {
+                if let Err(e) = unify_with_env(&right_type, &expected_fn, &self.env) {
                     self.errors.push(TypeError {
                         message: format!(
                             "Pipe target must be a function accepting {}: {}",
@@ -1904,7 +1936,7 @@ impl TypeChecker {
                 }
             },
             UnaryOp::Not => {
-                if let Err(e) = unify(&operand_type, &Type::Bool) {
+                if let Err(e) = unify_with_env(&operand_type, &Type::Bool, &self.env) {
                     self.errors.push(TypeError {
                         message: format!("Operator '!' requires Bool operand: {}", e),
                         span,
@@ -1955,7 +1987,7 @@ impl TypeChecker {
             self.current_effects.clone(),
         );
 
-        match unify(&func_type, &expected_fn) {
+        match unify_with_env(&func_type, &expected_fn, &self.env) {
             Ok(subst) => result_type.apply(&subst),
             Err(e) => {
                 // Provide more detailed error message based on the type of mismatch
@@ -2032,7 +2064,7 @@ impl TypeChecker {
                     let result_type = Type::var();
                     let expected_fn = Type::function(arg_types, result_type.clone());
 
-                    if let Err(e) = unify(field_type, &expected_fn) {
+                    if let Err(e) = unify_with_env(field_type, &expected_fn, &self.env) {
                         self.errors.push(TypeError {
                             message: format!(
                                 "Type mismatch in {}.{} call: {}",
@@ -2104,7 +2136,7 @@ impl TypeChecker {
                 for (i, (arg_type, (_, param_type))) in
                     arg_types.iter().zip(op.params.iter()).enumerate()
                 {
-                    if let Err(e) = unify(arg_type, param_type) {
+                    if let Err(e) = unify_with_env(arg_type, param_type, &self.env) {
                         self.errors.push(TypeError {
                             message: format!(
                                 "Argument {} of '{}.{}' has type {}, expected {}: {}",
@@ -2137,6 +2169,7 @@ impl TypeChecker {
 
     fn infer_field(&mut self, object: &Expr, field: &Ident, span: Span) -> Type {
         let object_type = self.infer_expr(object);
+        let object_type = self.env.expand_type_alias(&object_type);
 
         match &object_type {
             Type::Record(fields) => match fields.iter().find(|(n, _)| n == &field.name) {
@@ -2217,7 +2250,7 @@ impl TypeChecker {
         // Check return type if specified
         let ret_type = if let Some(rt) = return_type {
             let declared = self.resolve_type(rt);
-            if let Err(e) = unify(&body_type, &declared) {
+            if let Err(e) = unify_with_env(&body_type, &declared, &self.env) {
                 self.errors.push(TypeError {
                     message: format!(
                         "Lambda body type {} doesn't match declared {}: {}",
@@ -2283,7 +2316,7 @@ impl TypeChecker {
         span: Span,
     ) -> Type {
         let cond_type = self.infer_expr(condition);
-        if let Err(e) = unify(&cond_type, &Type::Bool) {
+        if let Err(e) = unify_with_env(&cond_type, &Type::Bool, &self.env) {
             self.errors.push(TypeError {
                 message: format!("If condition must be Bool, got {}: {}", cond_type, e),
                 span: condition.span(),
@@ -2293,7 +2326,7 @@ impl TypeChecker {
         let then_type = self.infer_expr(then_branch);
         let else_type = self.infer_expr(else_branch);
 
-        match unify(&then_type, &else_type) {
+        match unify_with_env(&then_type, &else_type, &self.env) {
             Ok(subst) => then_type.apply(&subst),
             Err(e) => {
                 self.errors.push(TypeError {
@@ -2334,7 +2367,7 @@ impl TypeChecker {
             // Check guard if present
             if let Some(ref guard) = arm.guard {
                 let guard_type = self.infer_expr(guard);
-                if let Err(e) = unify(&guard_type, &Type::Bool) {
+                if let Err(e) = unify_with_env(&guard_type, &Type::Bool, &self.env) {
                     self.errors.push(TypeError {
                         message: format!("Match guard must be Bool: {}", e),
                         span: guard.span(),
@@ -2350,7 +2383,7 @@ impl TypeChecker {
             match &result_type {
                 None => result_type = Some(body_type),
                 Some(prev) => {
-                    if let Err(e) = unify(prev, &body_type) {
+                    if let Err(e) = unify_with_env(prev, &body_type, &self.env) {
                         self.errors.push(TypeError {
                             message: format!(
                                 "Match arm has incompatible type: expected {}, got {}: {}",
@@ -2400,7 +2433,7 @@ impl TypeChecker {
 
             Pattern::Literal(lit) => {
                 let lit_type = self.infer_literal(lit);
-                if let Err(e) = unify(&lit_type, expected) {
+                if let Err(e) = unify_with_env(&lit_type, expected, &self.env) {
                     self.errors.push(TypeError {
                         message: format!("Pattern literal type mismatch: {}", e),
                         span: lit.span,
@@ -2414,7 +2447,7 @@ impl TypeChecker {
                 // For now, handle Option specially
                 match name.name.as_str() {
                     "None" => {
-                        if let Err(e) = unify(expected, &Type::Option(Box::new(Type::var()))) {
+                        if let Err(e) = unify_with_env(expected, &Type::Option(Box::new(Type::var())), &self.env) {
                             self.errors.push(TypeError {
                                 message: format!(
                                     "None pattern doesn't match type {}: {}",
@@ -2427,7 +2460,7 @@ impl TypeChecker {
                     }
                     "Some" => {
                         let inner_type = Type::var();
-                        if let Err(e) = unify(expected, &Type::Option(Box::new(inner_type.clone())))
+                        if let Err(e) = unify_with_env(expected, &Type::Option(Box::new(inner_type.clone())), &self.env)
                         {
                             self.errors.push(TypeError {
                                 message: format!(
@@ -2456,7 +2489,7 @@ impl TypeChecker {
 
             Pattern::Tuple { elements, span } => {
                 let element_types: Vec<Type> = elements.iter().map(|_| Type::var()).collect();
-                if let Err(e) = unify(expected, &Type::Tuple(element_types.clone())) {
+                if let Err(e) = unify_with_env(expected, &Type::Tuple(element_types.clone()), &self.env) {
                     self.errors.push(TypeError {
                         message: format!("Tuple pattern doesn't match type {}: {}", expected, e),
                         span: *span,
@@ -2506,7 +2539,7 @@ impl TypeChecker {
 
                     if let Some(type_expr) = typ {
                         let declared = self.resolve_type(type_expr);
-                        if let Err(e) = unify(&value_type, &declared) {
+                        if let Err(e) = unify_with_env(&value_type, &declared, &self.env) {
                             self.errors.push(TypeError {
                                 message: format!(
                                     "Variable '{}' has type {}, but declared type is {}: {}",
@@ -2527,12 +2560,46 @@ impl TypeChecker {
         self.infer_expr(result)
     }
 
-    fn infer_record(&mut self, fields: &[(Ident, Expr)], _span: Span) -> Type {
+    fn infer_record(
-        let field_types: Vec<(String, Type)> = fields
+        &mut self,
+        spread: Option<&Expr>,
+        fields: &[(Ident, Expr)],
+        span: Span,
+    ) -> Type {
+        // Start with spread fields if present
+        let mut field_types: Vec<(String, Type)> = if let Some(spread_expr) = spread {
+            let spread_type = self.infer_expr(spread_expr);
+            match spread_type {
+                Type::Record(spread_fields) => spread_fields,
+                _ => {
+                    self.errors.push(TypeError {
+                        message: format!(
+                            "Spread expression must be a record type, got {}",
+                            spread_type
+                        ),
+                        span,
+                    });
+                    Vec::new()
+                }
+            }
+        } else {
+            Vec::new()
+        };
+
+        // Apply explicit field overrides
+        let explicit_types: Vec<(String, Type)> = fields
             .iter()
             .map(|(name, expr)| (name.name.clone(), self.infer_expr(expr)))
             .collect();
 
+        for (name, typ) in explicit_types {
+            if let Some(existing) = field_types.iter_mut().find(|(n, _)| n == &name) {
+                existing.1 = typ;
+            } else {
+                field_types.push((name, typ));
+            }
+        }
+
         Type::Record(field_types)
     }
 
@@ -2549,7 +2616,7 @@ impl TypeChecker {
         let first_type = self.infer_expr(&elements[0]);
         for elem in &elements[1..] {
             let elem_type = self.infer_expr(elem);
-            if let Err(e) = unify(&first_type, &elem_type) {
+            if let Err(e) = unify_with_env(&first_type, &elem_type, &self.env) {
                 self.errors.push(TypeError {
                     message: format!("List elements must have same type: {}", e),
                     span,
@@ -2855,7 +2922,7 @@ impl TypeChecker {
             // Check return type matches if specified
             if let Some(ref return_type_expr) = impl_method.return_type {
                 let return_type = self.resolve_type(return_type_expr);
-                if let Err(e) = unify(&body_type, &return_type) {
+                if let Err(e) = unify_with_env(&body_type, &return_type, &self.env) {
                     self.errors.push(TypeError {
                         message: format!(
                             "Method '{}' body has type {}, but declared return type is {}: {}",

src/types.rs

@@ -1887,6 +1887,18 @@ impl TypeEnv {
                 "round".to_string(),
                 Type::function(vec![Type::var()], Type::Int),
             ),
+            (
+                "sin".to_string(),
+                Type::function(vec![Type::Float], Type::Float),
+            ),
+            (
+                "cos".to_string(),
+                Type::function(vec![Type::Float], Type::Float),
+            ),
+            (
+                "atan2".to_string(),
+                Type::function(vec![Type::Float, Type::Float], Type::Float),
+            ),
         ]);
         env.bind("Math", TypeScheme::mono(math_module_type));