miniscript: use new TRUE/FALSE constants throughout the codebase

This eliminates a bunch of error paths, which is nice.

Author: apoelstra

src/interpreter/inner.rs

@@ -46,12 +46,8 @@ fn script_from_stack_elem<Ctx: ScriptContext>(
             Miniscript::parse_with_ext(bitcoin::Script::from_bytes(sl), &ExtParams::allow_all())
                 .map_err(Error::from)
         }
-        stack::Element::Satisfied => {
-            Miniscript::from_ast(crate::Terminal::True).map_err(Error::from)
-        }
-        stack::Element::Dissatisfied => {
-            Miniscript::from_ast(crate::Terminal::False).map_err(Error::from)
-        }
+        stack::Element::Satisfied => Ok(Miniscript::TRUE),
+        stack::Element::Dissatisfied => Ok(Miniscript::FALSE),
     }
 }
 

src/miniscript/astelem.rs

@@ -332,7 +332,7 @@ impl<Pk: crate::FromStrKey, Ctx: ScriptContext> crate::expression::FromTree for
             ("and_n", 2) => Ok(Terminal::AndOr(
                 expression::FromTree::from_tree(&top.args[0])?,
                 expression::FromTree::from_tree(&top.args[1])?,
-                Arc::new(Miniscript::from_ast(Terminal::False)?),
+                Arc::new(Miniscript::FALSE),
             )),
             ("andor", 3) => Ok(Terminal::AndOr(
                 expression::FromTree::from_tree(&top.args[0])?,
@@ -401,24 +401,9 @@ impl<Pk: crate::FromStrKey, Ctx: ScriptContext> crate::expression::FromTree for
                 'v' => unwrapped = Terminal::Verify(Arc::new(ms)),
                 'j' => unwrapped = Terminal::NonZero(Arc::new(ms)),
                 'n' => unwrapped = Terminal::ZeroNotEqual(Arc::new(ms)),
-                't' => {
-                    unwrapped = Terminal::AndV(
-                        Arc::new(ms),
-                        Arc::new(Miniscript::from_ast(Terminal::True)?),
-                    )
-                }
-                'u' => {
-                    unwrapped = Terminal::OrI(
-                        Arc::new(ms),
-                        Arc::new(Miniscript::from_ast(Terminal::False)?),
-                    )
-                }
-                'l' => {
-                    unwrapped = Terminal::OrI(
-                        Arc::new(Miniscript::from_ast(Terminal::False)?),
-                        Arc::new(ms),
-                    )
-                }
+                't' => unwrapped = Terminal::AndV(Arc::new(ms), Arc::new(Miniscript::TRUE)),
+                'u' => unwrapped = Terminal::OrI(Arc::new(ms), Arc::new(Miniscript::FALSE)),
+                'l' => unwrapped = Terminal::OrI(Arc::new(Miniscript::FALSE), Arc::new(ms)),
                 x => return Err(Error::UnknownWrapper(x)),
             }
         }

src/policy/compiler.rs

@@ -530,27 +530,13 @@ fn all_casts<Pk: MiniscriptKey, Ctx: ScriptContext>() -> [Cast<Pk, Ctx>; 10] {
         },
         Cast {
             ext_data: types::ExtData::cast_likely,
-            node: |ms| {
-                Terminal::OrI(
-                    Arc::new(
-                        Miniscript::from_ast(Terminal::False).expect("False Miniscript creation"),
-                    ),
-                    ms,
-                )
-            },
+            node: |ms| Terminal::OrI(Arc::new(Miniscript::FALSE), ms),
             ast_type: types::Type::cast_likely,
             comp_ext_data: CompilerExtData::cast_likely,
         },
         Cast {
             ext_data: types::ExtData::cast_unlikely,
-            node: |ms| {
-                Terminal::OrI(
-                    ms,
-                    Arc::new(
-                        Miniscript::from_ast(Terminal::False).expect("False Miniscript creation"),
-                    ),
-                )
-            },
+            node: |ms| Terminal::OrI(ms, Arc::new(Miniscript::FALSE)),
             ast_type: types::Type::cast_unlikely,
             comp_ext_data: CompilerExtData::cast_unlikely,
         },
@@ -568,14 +554,7 @@ fn all_casts<Pk: MiniscriptKey, Ctx: ScriptContext>() -> [Cast<Pk, Ctx>; 10] {
         },
         Cast {
             ext_data: types::ExtData::cast_true,
-            node: |ms| {
-                Terminal::AndV(
-                    ms,
-                    Arc::new(
-                        Miniscript::from_ast(Terminal::True).expect("True Miniscript creation"),
-                    ),
-                )
-            },
+            node: |ms| Terminal::AndV(ms, Arc::new(Miniscript::TRUE)),
             ast_type: types::Type::cast_true,
             comp_ext_data: CompilerExtData::cast_true,
         },