1 files changed, 98 insertions, 0 deletions

diff --git a/crates/ra_analysis/src/completion/complete_dot.rs b/crates/ra_analysis/src/completion/complete_dot.rs
new file mode 100644
index 000000000..93d657576
--- /dev/null
+++ b/crates/ra_analysis/src/completion/complete_dot.rs
@@ -0,0 +1,98 @@
+use ra_syntax::ast::AstNode;
+use hir::{Ty, Def};
+
+use crate::Cancelable;
+use crate::completion::{CompletionContext, Completions, CompletionKind, CompletionItem, CompletionItemKind};
+
+/// Complete dot accesses, i.e. fields or methods (currently only fields).
+pub(super) fn complete_dot(acc: &mut Completions, ctx: &CompletionContext) -> Cancelable<()> {
+    let module = if let Some(module) = &ctx.module {
+        module
+    } else {
+        return Ok(());
+    };
+    let function = if let Some(fn_def) = ctx.enclosing_fn {
+        hir::source_binder::function_from_module(ctx.db, module, fn_def)
+    } else {
+        return Ok(());
+    };
+    let receiver = if let Some(receiver) = ctx.dot_receiver {
+        receiver
+    } else {
+        return Ok(());
+    };
+    let infer_result = function.infer(ctx.db)?;
+    let receiver_ty = if let Some(ty) = infer_result.type_of_node(receiver.syntax()) {
+        ty
+    } else {
+        return Ok(());
+    };
+    if !ctx.is_method_call {
+        complete_fields(acc, ctx, receiver_ty)?;
+    }
+    Ok(())
+}
+
+fn complete_fields(acc: &mut Completions, ctx: &CompletionContext, receiver: Ty) -> Cancelable<()> {
+    // TODO: autoderef etc.
+    match receiver {
+        Ty::Adt { def_id, .. } => {
+            match def_id.resolve(ctx.db)? {
+                Def::Struct(s) => {
+                    let variant_data = s.variant_data(ctx.db)?;
+                    for field in variant_data.fields() {
+                        CompletionItem::new(CompletionKind::Reference, field.name().to_string())
+                            .kind(CompletionItemKind::Field)
+                            .add_to(acc);
+                    }
+                }
+                // TODO unions
+                _ => {}
+            }
+        }
+        Ty::Tuple(fields) => {
+            for (i, _ty) in fields.iter().enumerate() {
+                CompletionItem::new(CompletionKind::Reference, i.to_string())
+                    .kind(CompletionItemKind::Field)
+                    .add_to(acc);
+            }
+        }
+        _ => {}
+    };
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::completion::*;
+
+    fn check_ref_completion(code: &str, expected_completions: &str) {
+        check_completion(code, expected_completions, CompletionKind::Reference);
+    }
+
+    #[test]
+    fn test_struct_field_completion() {
+        check_ref_completion(
+            r"
+            struct A { the_field: u32 }
+            fn foo(a: A) {
+               a.<|>
+            }
+            ",
+            r#"the_field"#,
+        );
+    }
+
+    #[test]
+    fn test_no_struct_field_completion_for_method_call() {
+        check_ref_completion(
+            r"
+            struct A { the_field: u32 }
+            fn foo(a: A) {
+               a.<|>()
+            }
+            ",
+            r#""#,
+        );
+    }
+}