hygiene: Remove `Option`s from functions returning `ExpnInfo`

The expansion info is not optional and should always exist

2 files changed, 49 insertions, 72 deletions

diff --git a/src/libsyntax_pos/hygiene.rs b/src/libsyntax_pos/hygiene.rs
index c832e058cdf..743bd437ee5 100644
--- a/src/libsyntax_pos/hygiene.rs
+++ b/src/libsyntax_pos/hygiene.rs
@@ -112,8 +112,8 @@ impl ExpnId {
     }
 
     #[inline]
-    pub fn expn_info(self) -> Option<ExpnInfo> {
-        HygieneData::with(|data| data.expn_info(self).cloned())
+    pub fn expn_info(self) -> ExpnInfo {
+        HygieneData::with(|data| data.expn_info(self).clone())
     }
 
     #[inline]
@@ -139,12 +139,9 @@ impl ExpnId {
     #[inline]
     pub fn looks_like_proc_macro_derive(self) -> bool {
         HygieneData::with(|data| {
-            if data.default_transparency(self) == Transparency::Opaque {
-                if let Some(expn_info) = data.expn_info(self) {
-                    if let ExpnKind::Macro(MacroKind::Derive, _) = expn_info.kind {
-                        return true;
-                    }
-                }
+            let expn_info = data.expn_info(self);
+            if let ExpnKind::Macro(MacroKind::Derive, _) = expn_info.kind {
+                return expn_info.default_transparency == Transparency::Opaque;
             }
             false
         })
@@ -190,16 +187,9 @@ impl HygieneData {
         self.expn_data[expn_id.0 as usize].parent
     }
 
-    fn expn_info(&self, expn_id: ExpnId) -> Option<&ExpnInfo> {
-        if expn_id != ExpnId::root() {
-            Some(self.expn_data[expn_id.0 as usize].expn_info.as_ref()
-                     .expect("no expansion info for an expansion ID"))
-        } else {
-            // FIXME: Some code relies on `expn_info().is_none()` meaning "no expansion".
-            // Introduce a method for checking for "no expansion" instead and always return
-            // `ExpnInfo` from this function instead of the `Option`.
-            None
-        }
+    fn expn_info(&self, expn_id: ExpnId) -> &ExpnInfo {
+        self.expn_data[expn_id.0 as usize].expn_info.as_ref()
+            .expect("no expansion info for an expansion ID")
     }
 
     fn is_descendant_of(&self, mut expn_id: ExpnId, ancestor: ExpnId) -> bool {
@@ -212,12 +202,6 @@ impl HygieneData {
         true
     }
 
-    fn default_transparency(&self, expn_id: ExpnId) -> Transparency {
-        self.expn_info(expn_id).map_or(
-            Transparency::SemiTransparent, |einfo| einfo.default_transparency
-        )
-    }
-
     fn modern(&self, ctxt: SyntaxContext) -> SyntaxContext {
         self.syntax_context_data[ctxt.0 as usize].opaque
     }
@@ -256,11 +240,7 @@ impl HygieneData {
 
     fn walk_chain(&self, mut span: Span, to: SyntaxContext) -> Span {
         while span.from_expansion() && span.ctxt() != to {
-            if let Some(info) = self.expn_info(self.outer_expn(span.ctxt())) {
-                span = info.call_site;
-            } else {
-                break;
-            }
+            span = self.expn_info(self.outer_expn(span.ctxt())).call_site;
         }
         span
     }
@@ -275,7 +255,9 @@ impl HygieneData {
 
     fn apply_mark(&mut self, ctxt: SyntaxContext, expn_id: ExpnId) -> SyntaxContext {
         assert_ne!(expn_id, ExpnId::root());
-        self.apply_mark_with_transparency(ctxt, expn_id, self.default_transparency(expn_id))
+        self.apply_mark_with_transparency(
+            ctxt, expn_id, self.expn_info(expn_id).default_transparency
+        )
     }
 
     fn apply_mark_with_transparency(&mut self, ctxt: SyntaxContext, expn_id: ExpnId,
@@ -285,8 +267,7 @@ impl HygieneData {
             return self.apply_mark_internal(ctxt, expn_id, transparency);
         }
 
-        let call_site_ctxt =
-            self.expn_info(expn_id).map_or(SyntaxContext::root(), |info| info.call_site.ctxt());
+        let call_site_ctxt = self.expn_info(expn_id).call_site.ctxt();
         let mut call_site_ctxt = if transparency == Transparency::SemiTransparent {
             self.modern(call_site_ctxt)
         } else {
@@ -581,17 +562,17 @@ impl SyntaxContext {
     /// `ctxt.outer_expn_info()` is equivalent to but faster than
     /// `ctxt.outer_expn().expn_info()`.
     #[inline]
-    pub fn outer_expn_info(self) -> Option<ExpnInfo> {
-        HygieneData::with(|data| data.expn_info(data.outer_expn(self)).cloned())
+    pub fn outer_expn_info(self) -> ExpnInfo {
+        HygieneData::with(|data| data.expn_info(data.outer_expn(self)).clone())
     }
 
     /// `ctxt.outer_expn_with_info()` is equivalent to but faster than
     /// `{ let outer = ctxt.outer_expn(); (outer, outer.expn_info()) }`.
     #[inline]
-    pub fn outer_expn_with_info(self) -> (ExpnId, Option<ExpnInfo>) {
+    pub fn outer_expn_with_info(self) -> (ExpnId, ExpnInfo) {
         HygieneData::with(|data| {
             let outer = data.outer_expn(self);
-            (outer, data.expn_info(outer).cloned())
+            (outer, data.expn_info(outer).clone())
         })
     }
 
@@ -681,6 +662,11 @@ impl ExpnInfo {
             ..ExpnInfo::default(kind, call_site, edition)
         }
     }
+
+    #[inline]
+    pub fn is_root(&self) -> bool {
+        if let ExpnKind::Root = self.kind { true } else { false }
+    }
 }
 
 /// Expansion kind.
diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index 7c8539198b9..7af426eaa13 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -355,20 +355,20 @@ impl Span {
     /// Returns the source span -- this is either the supplied span, or the span for
     /// the macro callsite that expanded to it.
     pub fn source_callsite(self) -> Span {
-        self.ctxt().outer_expn_info().map(|info| info.call_site.source_callsite()).unwrap_or(self)
+        let expn_info = self.ctxt().outer_expn_info();
+        if !expn_info.is_root() { expn_info.call_site.source_callsite() } else { self }
     }
 
     /// The `Span` for the tokens in the previous macro expansion from which `self` was generated,
     /// if any.
     pub fn parent(self) -> Option<Span> {
-        self.ctxt().outer_expn_info().map(|i| i.call_site)
+        let expn_info = self.ctxt().outer_expn_info();
+        if !expn_info.is_root() { Some(expn_info.call_site) } else { None }
     }
 
     /// Edition of the crate from which this span came.
     pub fn edition(self) -> edition::Edition {
-        self.ctxt().outer_expn_info().map_or_else(|| {
-            Edition::from_session()
-        }, |einfo| einfo.edition)
+        self.ctxt().outer_expn_info().edition
     }
 
     #[inline]
@@ -387,49 +387,39 @@ impl Span {
     /// else returns the `ExpnInfo` for the macro definition
     /// corresponding to the source callsite.
     pub fn source_callee(self) -> Option<ExpnInfo> {
-        fn source_callee(info: ExpnInfo) -> ExpnInfo {
-            match info.call_site.ctxt().outer_expn_info() {
-                Some(info) => source_callee(info),
-                None => info,
-            }
+        fn source_callee(expn_info: ExpnInfo) -> ExpnInfo {
+            let next_expn_info = expn_info.call_site.ctxt().outer_expn_info();
+            if !next_expn_info.is_root() { source_callee(next_expn_info) } else { expn_info }
         }
-        self.ctxt().outer_expn_info().map(source_callee)
+        let expn_info = self.ctxt().outer_expn_info();
+        if !expn_info.is_root() { Some(source_callee(expn_info)) } else { None }
     }
 
     /// Checks if a span is "internal" to a macro in which `#[unstable]`
     /// items can be used (that is, a macro marked with
     /// `#[allow_internal_unstable]`).
     pub fn allows_unstable(&self, feature: Symbol) -> bool {
-        match self.ctxt().outer_expn_info() {
-            Some(info) => info
-                .allow_internal_unstable
-                .map_or(false, |features| features.iter().any(|&f|
-                    f == feature || f == sym::allow_internal_unstable_backcompat_hack
-                )),
-            None => false,
-        }
+        self.ctxt().outer_expn_info().allow_internal_unstable.map_or(false, |features| {
+            features.iter().any(|&f| {
+                f == feature || f == sym::allow_internal_unstable_backcompat_hack
+            })
+        })
     }
 
     /// Checks if this span arises from a compiler desugaring of kind `kind`.
     pub fn is_desugaring(&self, kind: DesugaringKind) -> bool {
-        match self.ctxt().outer_expn_info() {
-            Some(info) => match info.kind {
-                ExpnKind::Desugaring(k) => k == kind,
-                _ => false,
-            },
-            None => false,
+        match self.ctxt().outer_expn_info().kind {
+            ExpnKind::Desugaring(k) => k == kind,
+            _ => false,
         }
     }
 
     /// Returns the compiler desugaring that created this span, or `None`
     /// if this span is not from a desugaring.
     pub fn desugaring_kind(&self) -> Option<DesugaringKind> {
-        match self.ctxt().outer_expn_info() {
-            Some(info) => match info.kind {
-                ExpnKind::Desugaring(k) => Some(k),
-                _ => None
-            },
-            None => None
+        match self.ctxt().outer_expn_info().kind {
+            ExpnKind::Desugaring(k) => Some(k),
+            _ => None
         }
     }
 
@@ -437,16 +427,17 @@ impl Span {
     /// can be used without triggering the `unsafe_code` lint
     //  (that is, a macro marked with `#[allow_internal_unsafe]`).
     pub fn allows_unsafe(&self) -> bool {
-        match self.ctxt().outer_expn_info() {
-            Some(info) => info.allow_internal_unsafe,
-            None => false,
-        }
+        self.ctxt().outer_expn_info().allow_internal_unsafe
     }
 
     pub fn macro_backtrace(mut self) -> Vec<MacroBacktrace> {
         let mut prev_span = DUMMY_SP;
         let mut result = vec![];
-        while let Some(info) = self.ctxt().outer_expn_info() {
+        loop {
+            let info = self.ctxt().outer_expn_info();
+            if info.is_root() {
+                break;
+            }
             // Don't print recursive invocations.
             if !info.call_site.source_equal(&prev_span) {
                 let (pre, post) = match info.kind {